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Astronomy

Hubble celebrates 35th year in orbit

By ScientifiCult 23 April 2025

$The planetary nebula NGC 2899 is shaped like a single macaroni noodle, with its edges pointed up, but its edge-on central torus is semi-transparent in the middle. The top and bottom edges are thick and orange. The center is semi-transparent blue and green. The wider central region looks roughly like a moth, also filled with semi-transparent blue and green. There are two pinpoint-like white stars with diffraction spikes toward the center. Immediately below them, slightly toward the right, is a smaller blue orb, a central star. The next layer of gas and dust is whiter, with some thicker pillars that look like they are rising up at bottom center. The colour fades into reds and purples, and then to orange$

Hubble celebrates 35th year in orbit

In celebration of the NASA/ESA Hubble Space Telescope’s 35 years in Earth orbit, an assortment of compelling images have been released today that were recently taken by Hubble. This stretches from the planet Mars to dramatic images of stellar birth and death, to a magnificent neighbouring galaxy. After over three decades of perusing the restless universe, Hubble remains a household word as the most well-recognized telescope in scientific history.

Astronomers knew that placing a telescope above Earth’s blurry atmosphere would allow for them to behold the Universe like never before. Hubble’s view would be ten times sharper than conventional ground-based telescopes of the time. Its high sensitivity would uncover objects more than one-billionth the brightness of the faintest stars seen by the human eye. Unfiltered by Earth’s atmosphere, its broad wavelength coverage would stretch from ultraviolet to near-infrared light. Glorious celestial wonders would come into focus. Moreover, Hubble would be an audacious leap forward in human imagination, engineering prowess, and boundless curiosity.

Before Hubble, no generation ever had access to unimaginably vibrant views of space, stretching almost all the way back to almost the beginning of time. For most of history, the complexity and extent of the vast cosmos was left largely to human imagination. But Hubble entered the final sprint in the race to the edge of the visible Universe. In the early 1920s, the telescope’s namesake, astronomer Edwin Hubble, started this marathon with the discovery of galaxies outside of our Milky Way.

Hubble today is at the peak of its scientific return thanks to the dedication, perseverance and skills of engineers, scientists and mission operators. Astronaut shuttle crews gallantly chased and rendezvoused with Hubble on five servicing missions from 1993 to 2009. The astronauts, including ESA astronauts on two of the servicing missions, upgraded Hubble’s cameras, computers and other support systems.

By extending Hubble’s operational life the telescope has made nearly 1.7 million observations, looking at approximately 55,000 astronomical targets. Hubble discoveries have resulted in over 22,000 papers and over 1.3 million citations as of February 2025. All the data collected by Hubble is archived and currently adds up to over 400 terabytes. The demand for observing time remains very high with 6:1 oversubscriptions, making it one of the most in-demand observatories today.

Hubble’s long operational life has allowed astronomers to see astronomical changes spanning over three decades: seasonal variability on the planets in our solar system, black hole jets travelling at nearly the speed of light, stellar convulsions, asteroid collisions, expanding supernova bubbles, and much more.

A lasting legacy

Hubble’s legacy is the bridge between our past and future knowledge of a Universe that is unbelievably glorious, as well as rambunctious — with colliding galaxies, voracious black holes, and relentless stellar fireworks. Hubble, more than any other telescope, sees the Universe through the eyes of Einstein: microlensing, time-dilation, the cosmological constant, matter disappearing into a black hole, a source of gravitational waves.

Before 1990, powerful optical telescopes on Earth could see only halfway across the cosmos. Estimates for the age of the Universe disagreed by a big margin. Supermassive black holes were only suspected to be the powerhouses behind a rare zoo of energetic phenomena. Not a single planet had been seen around another star.

Among its long list of breakthroughs: Hubble’s deep fields unveiled myriad galaxies dating back to the early Universe; precisely measured the Universe’s expansion; found that supermassive black holes are common among galaxies; made the first measurement of the atmospheres of extrasolar planets; contributed to discovering dark energy, which is accelerating the Universe.

After three decades, Hubble remains a household word as the most well-recognized and celebrated scientific instrument in all of human history. Hubble’s discoveries and images have been nothing less than transformative for the public’s perception of the cosmos. Unlike any other telescope before it, Hubble has made astronomy very relevant, engaging, and accessible for people of all ages. Hubble became “the people’s telescope,” touching the minds as well as the emotions of hundreds of millions of humans around the globe.

A single Hubble snapshot can portray the Universe as awesome, mysterious, and beautiful—and at the same time chaotic, overwhelming, and foreboding. These pictures have become iconic, seminal, and timeless. They viscerally communicate the value of science: the awe and drive to seek understanding of our place in the cosmos. In commemoration NASA and ESA released images today of five astronomical targets that were selected for the celebration, ranging from planets to nebulae to galaxies.

The relentless pace of Hubble’s trailblazing discoveries kicked-started a new generation of space telescopes for the 21st century. The powerful James Webb Space Telescope may not have been built without Hubble revealing an “undiscovered country” of far-flung, seemingly countless galaxies. Hubble provided the first observational evidence that there was a lot for Webb to pursue in infrared wavelengths that reach even greater distances beyond Hubble’s gaze. Now, Hubble and Webb are often being used in complement to study everything from exoplanets to galaxy dynamics.

35th anniversary images

An assortment of compelling images have been released today that were recently taken by Hubble:

Mars: These are a combination of Hubble Space Telescope images of Mars taken from December 28th to 30th, 2024. At the midpoint of the observations, Mars was approximately 98 million kilometres from Earth. Thin water-ice clouds that are apparent in ultraviolet light give the Red Planet a frosty appearance. The icy northern polar cap was experiencing the start of Martian spring.

Composite shows four Hubble images in quarters. At top left is a crisp view of Mars in shades of orange, blues, and browns. At top right is planetary nebula NGC 2899, which is shaped like a single macaroni noodle, with its central torus appearing semi-transparent and blue/green, and top and bottom edges in orange. At bottom left is a tiny portion of the Rosette Nebula. Very dark gray material shaped like a V takes up the center. At bottom right is barred spiral galaxy NGC 5335 with a milky yellow center that forms a bar surrounded by multiple blue star-filled spiral that wrap up counterclockwise. — In celebration of the NASA/ESA Hubble Space Telescope’s 35 years in Earth orbit, an assortment of compelling images have been released today that were recently taken by Hubble: Upper left: The planet Mars as seen in late December 2024. Thin water-ice clouds, revealed by Hubble’s unique ultraviolet capability, give the Red Planet a frosty appearance. Upper right: Planetary nebula NGC 2899. This moth-like nebula is sculpted by the outflow of radiation and stellar winds from a dying star – a white dwarf – at the center. Lower left: The Rosette Nebula. This is a small portion of the huge star-forming region. Dark clouds of hydrogen gas laced with dust are silhouetted across the image. Lower right: The galaxy NGC 5335, which is a flocculent spiral galaxy with patchy streamers of star formation across its disc. A notable bar structure slices across the center of the galaxy. Credit: NASA, ESA, STScI

Two views of planet Mars on a black background of space observed by the Hubble Space Telescope. At left, text: December 28, 2024 20:00 UT. At right, text: December 29, 2024 13:18 UT. In both images, its atmosphere is clear and the surface appears detailed. Most of the planet is shades of orange. At left, the brightest orange area appears in the left half. At right, the brightest orange area is centered and takes on the rough shape of a sleeping mask. In both views, darker surface features are noticeable on the lower half of the planet. These have a mix of orange, blue, and gray hues. At the top and bottom, white regions mark the planet’s polar caps. The entire limb of the planet, its visible edge, has a blue hue. The blue doesn’t form an even circle at the edges, and appears thinner toward the left and right, and thicker in some areas. — This is a combination of Hubble Space Telescope images of Mars taken from December 28th to 30th, 2024. At the midpoint of the observations, Mars was approximately 98 million kilometres from Earth. Thin water-ice clouds that are apparent in ultraviolet light give the Red Planet a frosty appearance. The icy northern polar cap was experiencing the start of Martian spring. In the left image, the bright orange Tharsis plateau is visible with its chain of dormant volcanoes. The largest volcano, Olympus Mons, pokes above the clouds at the 10 o’clock position near the northwest limb. At an elevation of 21 000 metres, it is 2.5 times the height of Mt. Everest above sea level. Valles Marineris, Mars’ roughly 4,000 kilometre-long canyon system, is a dark, linear, horizontal feature near center left. In the right image, high-altitude evening clouds can be seen along the planet’s eastern limb. The 2,250-kilometre-wide Hellas basin, an ancient asteroid impact feature, appears far to the south. Most of the hemisphere is dominated by the classical “shark fin” feature, Syrtis Major. Credit: NASA, ESA, STScI

Two views of Mars. Top left text: Mars & Phobos, Hubble Space Telescope; filters in colors: F275W, purple; F410M, blue; F502N, green; F673N, red. Top image: December 28, 2024 20:00 UT. Most of the planet is shades of orange. The brightest orange area on the left half. At the top and bottom, white polar caps. Limb is blue. Text top center: northern polar cap, clouds. On planet, top to bottom, left to right: Arcadia Planitia, Tempe Terra, Acidalia Planitia; Olympus Monds; Tharsis Montes, Chryse Planitia; Valles Marineris, Terra Meridiana; Solus Planum; Argyre Planitia, Noachis Terra. To the right, dot: Phobos. Lower image: December 29, 2024 13:18 UT. Compass arrows at right, north pointing up, = east left. The planet has similar features; the brightest orange area is two centered two blobs. Text above Mars: northern polar cap, clouds. On-planet: Utopia Planitia; Arabia Terra, Syrtis Major; Terra Meridiani, Schiaparelli Crater, clouds; Noachis Terra, Huygens Crater, Syrtis Minor; Hellas Planitia. At left, dot: Phobos. — This pair of NASA/ESA Hubble Space Telescope images of Mars taken on 28 December (top) and 29 December (bottom) 2024. Each image shows a different side of the planet, with the accompanying moon Phobos. Various features are identified in the images, including the polar ice caps and clouds, as well as multiple terrestrial features. At the midpoint of the observations, Mars was approximately 98 million kilometres from Earth. Thin water-ice clouds that are apparent in ultraviolet light give the Red Planet a frosty appearance. The icy northern polar cap was experiencing the start of Martian spring. In the top image, the bright orange Tharsis plateau is visible with its chain of dormant volcanoes. The largest volcano, Olympus Mons, pokes above the clouds at the 10 o’clock position near the northwest limb. At an elevation of over 21 000 meters, it is 2.5 times the height of Mt. Everest above sea level. Valles Marineris, Mars’ over 4,000-kilometre-long canyon system, is a dark, linear, horizontal feature near center left. In the bottom image, high-altitude evening clouds can be seen along the planet’s eastern limb. The 2,250-kilometre-wide Hellas basin, an ancient asteroid impact feature, appears far to the south. Most of the hemisphere is dominated by the classical “shark fin” feature, Syrtis Major. Credit: NASA, ESA, STScI

Planetary nebula NGC 2899: This object has a diagonal, bipolar, cylindrical outflow of gas. This is propelled by radiation and stellar winds from a nearly 22 000 degree Celsius white dwarf at the center. In fact, there may be two companion stars that are interacting and sculpting the nebula, which is pinched in the middle by a fragmented ring or torus – looking like a half-eaten donut. It has a forest of gaseous “pillars” that point back to the source of radiation and stellar winds. The colors are from glowing hydrogen and oxygen. The nebula lies approximately 4,500 light-years away in the southern constellation Vela.

The planetary nebula NGC 2899 is shaped like a single macaroni noodle, with its edges pointed up, but its edge-on central torus is semi-transparent in the middle. The top and bottom edges are thick and orange. The center is semi-transparent blue and green. The wider central region looks roughly like a moth, also filled with semi-transparent blue and green. There are two pinpoint-like white stars with diffraction spikes toward the center. Immediately below them, slightly toward the right, is a smaller blue orb, a central star. The next layer of gas and dust is whiter, with some thicker pillars that look like they are rising up at bottom center. The colour fades into reds and purples, and then to orange — This Hubble Space Telescope image captures the beauty of the moth-like planetary nebula NGC 2899. This object has a diagonal, bipolar, cylindrical outflow of gas. This is propelled by radiation and stellar winds from a nearly 22 000 degree Celsius white dwarf at the center. In fact, there may be two companion stars that are interacting and sculpting the nebula, which is pinched in the middle by a fragmented ring or torus – looking like a half-eaten donut. It has a forest of gaseous “pillars” that point back to the source of radiation and stellar winds. The colours are from glowing hydrogen and oxygen. The nebula lies approximately 4,500 light-years away in the southern constellation Vela. Credit: NASA, ESA, STScI

This Hubble Space Telescope image captures the beauty of the moth-like planetary nebula NGC 2899. This object has a diagonal, bipolar, cylindrical outflow of gas. This is propelled by radiation and stellar winds from a nearly 22 000 degree Celsius white dwarf at the center. In fact, there may be two companion stars that are interacting and sculpting the nebula, which is pinched in the middle by a fragmented ring or torus – looking like a half-eaten donut. It has a forest of gaseous “pillars” that point back to the source of radiation and stellar winds. The colours are from glowing hydrogen and oxygen. The nebula lies approximately 4,500 light-years away in the southern constellation Vela. Credit: NASA, ESA, STScI

Rosette Nebula: This is a Hubble Space Telescope photo of a small portion of the Rosette Nebula, a huge star-forming region spanning 100 light-years across and located 5,200 light-years away. Hubble zooms into a small portion of the nebula that is only 4 light-years across (the approximate distance between our Sun and the neighbouring Alpha Centauri star system.) Dark clouds of hydrogen gas laced with dust are silhouetted across the image. The clouds are being eroded and shaped by the seething radiation from the cluster of larger stars in the center of the nebula (NGC 2440). An embedded star seen at the tip of a dark cloud in the upper right portion of the image is launching jets of plasma that are crashing into the cold cloud around it. The resulting shock wave is causing a red glow. The colors come from the presence of hydrogen, oxygen, and nitrogen.

A tiny portion of the Rosette Nebula. Very dark gray material shaped like a V extends from just below top left all the way down to the lower right corner and back up toward the top right. It looks like thick smoke that has billowed out irregularly, thicker along the line from top left to bottom right, and looser on the piece that goes toward the top right. Behind the dark gray on the left side, from the bottom left to top center, there is dust that looks like arced claw marks that appears in light orange and yellow. The background at top left is hazier and some blues are covered in semi-transparent orange wisps, which makes sections take on green hues. In the bottom right, the background is bluer. There are a few bright red and purple stars scattered along the right half, most toward the bottom. The largest star is at right-center, just at the edge. It is red and has four diffraction spikes. — This is a Hubble Space Telescope photo of a small portion of the Rosette Nebula, a huge star-forming region spanning 100 light-years across and located 5,200 light-years away. Hubble zooms into a small portion of the nebula that is only 4 light-years across (the approximate distance between our Sun and the neighbouring Alpha Centauri star system.) Dark clouds of hydrogen gas laced with dust are silhouetted across the image. The clouds are being eroded and shaped by the seething radiation from the cluster of larger stars in the center of the nebula (NGC 2440). An embedded star seen at the tip of a dark cloud in the upper right portion of the image is launching jets of plasma that are crashing into the cold cloud around it. The resulting shock wave is causing a red glow. The colours come from the presence of hydrogen, oxygen, and nitrogen. Credit: NASA, ESA, STScI

A square, ground-based observation of the entire Rosette Nebula. A large, diffuse donut shape primarily composed of light brown and gray gas and dust extends to the edges. Several bright blue stars are at its clearer center. There are innumerable small stars throughout the background, most of which are blue. A tiny box at center-left connects to a zoomed-in image of this region at bottom left from the Hubble Space Telescope. The Hubble image shows a dark gray V that extends from just below top left all the way down to the lower right corner and back up toward the top right. It looks like thick, irregular smoke. Behind the dark gray on the left side there are arced lines in light orange and yellow. The background at top left is hazier, the blues covered in semi-transparent orange wisps, making a few sections appear green. In the bottom right, the background is bluer. There are a few bright red and purple stars scattered along the right half. — The Rosette Nebula is a vast star-forming region, 100 light-years across, that lies at one end of a giant molecular cloud the constellation Monoceros. The nebula is estimated to contain around 10,000 solar masses. The nebula is located about 5,000 light-years away from Earth. Intense radiation from the young stars inside a cluster in the nebula causes the gasses to glow. The background image is from the Digitized Sky Survey, while the inset is a small portion of the nebula as photographed by the Hubble Space Telescope. Dark clouds of hydrogen gas laced with dust are silhouetted across the image. The colours come from the presence of hydrogen, oxygen, and nitrogen. Credit: NASA, ESA, STScI, DSS

This is a Hubble Space Telescope photo of a small portion of the Rosette Nebula, a huge star-forming region spanning 100 light-years across and located 5,200 light-years away. Hubble zooms into a small portion of the nebula that is only 4 light-years across (the approximate distance between our Sun and the neighbouring Alpha Centauri star system.) Dark clouds of hydrogen gas laced with dust are silhouetted across the image. The clouds are being eroded and shaped by the seething radiation from the cluster of larger stars in the center of the nebula (NGC 2440). An embedded star seen at the tip of a dark cloud in the upper right portion of the image is launching jets of plasma that are crashing into the cold cloud around it. The resulting shock wave is causing a red glow. The colours come from the presence of hydrogen, oxygen, and nitrogen. Credit: NASA, ESA, STScI

Barred Spiral Galaxy NGC 5335: This object is categorized as a flocculent spiral galaxy with patchy streamers of star formation across its disk. There is a striking lack of well-defined spiral arms that are commonly found among galaxies, including our Milky Way. A notable bar structure slices across the center of the galaxy. The bar channels gas inwards toward the galactic center, fueling star formation. Such bars are dynamic in galaxies and may come and go over two-billion-year intervals. They appear in about 30 percent of observed galaxies, including our Milky Way.

Barred spiral galaxy NGC 5335 observed by the Hubble Space Telescope takes up the majority of the view. At its center is a milky yellow, flattened oval that extends bottom left to top. Within the oval is a bright central region that looks circular, with the very center the brightest. In the bright central region is what looks like a bar, extending from top left to bottom right. Around this is a thick swath of blue stars speckled with white regions. Multiple arms wrap up and around in a counterclockwise direction, becoming fainter the farther out they are. Both the white core and the spiral arms are intertwined with dark streaks of dust. The background of space is black. Thousands of distant galaxies in an array of colors are speckled throughout. — The Hubble Space Telescope captured in exquisite detail a face-on view of a remarkable-looking galaxy. NGC 5335 is categorized as a flocculent spiral galaxy with patchy streamers of star formation across its disk. There is a striking lack of well-defined spiral arms that are commonly found among galaxies, including our Milky Way. A notable bar structure slices across the center of the galaxy. The bar channels gas inwards toward the galactic center, fueling star formation. Such bars are dynamic in galaxies and may come and go over two-billion-year intervals. They appear in about 30 percent of observed galaxies, including our Milky Way. Credit: NASA, ESA, STScI

The Hubble Space Telescope captured in exquisite detail a face-on view of a remarkable-looking galaxy. NGC 5335 is categorized as a flocculent spiral galaxy with patchy streamers of star formation across its disk. There is a striking lack of well-defined spiral arms that are commonly found among galaxies, including our Milky Way. A notable bar structure slices across the center of the galaxy. The bar channels gas inwards toward the galactic center, fueling star formation. Such bars are dynamic in galaxies and may come and go over two-billion-year intervals. They appear in about 30 percent of observed galaxies, including our Milky Way. Credit: NASA, ESA, STScI

Hubble’s science and discoveries in recent years

Even at the impressive age of 35, there has been no slowdown in the research and new discoveries made using Hubble — if anything, the opposite. Astronomers from Europe make intensive use of the telescope, with the share of observing time awarded to European-led programmes being consistently above the 15% guaranteed by ESA’s participation in the Hubble mission thanks to their many proposals with strong scientific merit. This has led directly to discoveries including evidence for an intermediate-mass black hole in Omega Centauri, a precursor to the earliest supermassive black holes, a bizarre explosion of extraordinarily bright light originating far from any host galaxy, hydrogen burning in white dwarf stars, and the absence of Population III stars as far back in time as Hubble can see. A particular highlight, and a demonstration of Hubble’s incredible capabilities, was the discovery in 2022 of Earendel. The most distant single star ever seen, Earendel is viewed 12.9 billion years into the past when the Universe was under a billion years old.

Benefitting from Hubble’s long operational life, the OPAL programme celebrated a decade studying the Solar System’s outer planets. Discoveries such as evidence for water vapour on Jupiter’s moons Europa and Ganymede, “spokes” in Saturn’s rings, the size of Jupiter’s Great Red Spot, and the colours of Uranus and Neptune are just some that have resulted. Smaller Solar System bodies got attention from Hubble as well — not least the asteroid Dimorphos, target of the DART asteroid redirection test. Hubble took images of Dimorphos before and after the impact alongside Webb, later producing a movie of the debris and spotting ejected boulders. A citizen science project also discovered thousands of asteroid trails in over two decades of archived Hubble snapshots.

Beyond the Solar System, Hubble proved its continued importance in the rapidly-growing field of research into exoplanets. It studied weather patterns in an exoplanet’s atmosphere, saw a new atmosphere being formed around a rocky exoplanet similar to Earth, and found a small exoplanet with water vapour in its atmosphere. Also completed in 2021 was a compilation of supernova host galaxies from 18 years of study, images that were used to measure the Hubble constant to its highest accuracy yet. This year too brought the culmination of the largest ever photomosaic of the Andromeda Galaxy, created from ten years of Hubble observations of our near neighbour.

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The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the Universe. Hubble is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.

Press release from ESA Hubble.

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Astronomy

Hubble spies a cosmic pillar in the Eagle Nebula, or Messier 16

By ScientifiCult 18 April 2025

Hubble spies a cosmic pillar in the Eagle Nebula, also known as Messier 16

In anticipation of the upcoming 35th anniversary of the NASA/ESA Hubble Space Telescope, ESA/Hubble is continuing the celebrations with a new view of the Eagle Nebula. This vast stellar nursery displays a towering spire of cosmic gas and dust that incorporates new data processing techniques developed since an image of this region was last released two decades ago.

Does this Hubble image of a sculpted pillar of gas and dust look to you like a curling party streamer, a plume of smoke from a blown-out candle, or an unusual balloon? Regardless of what you see when you gaze at this cosmic cloud, this new portrait is a cause for celebration.

As part of ESA/Hubble’s 35th anniversary celebrations, a new image series is being shared to revisit stunning Hubble targets that were previously released. New images of NGC 346 and the Sombrero Galaxy have already been published. Now, ESA/Hubble is revisiting the Eagle Nebula (originally published in 2005 as part of Hubble’s 15th anniversary celebrations) with new image processing techniques.

Unfurling along the length of the image is a pillar of cold gas and dust that is 9.5 light-years tall. As enormous as this dusty pillar is, it’s just one small piece of the greater Eagle Nebula, which is also called Messier 16. The name Messier 16 comes from the French astronomer Charles Messier, a comet hunter who compiled a catalogue of deep-sky objects that could be mistaken for comets.

The name Eagle Nebula was inspired by the nebula’s appearance. The edge of this shining nebula is shaped by dark clouds like this one, giving it the appearance of an eagle spreading its wings.

Not too far from the region pictured here are the famous Pillars of Creation, which Hubble has photographed multiple times, with images released in 1995 and 2015.

The heart of the nebula, which is located beyond the edge of this image, is home to a cluster of young stars. These stars have excavated an immense cavity in the centre of the nebula, shaping otherworldly pillars and globules of dusty gas. This particular feature extends like a pointing finger toward the centre of the nebula and the rich young star cluster embedded there.

The Eagle Nebula is one of many nebulae in the Milky Way that are known for their sculpted, dusty clouds. Nebulae take on these fantastic shapes when exposed to powerful radiation and winds from infant stars. Regions with denser gas are more able to withstand the onslaught of radiation and stellar winds from young stars, and these dense areas remain as dusty sculptures like the starry pillar shown here.

This image was developed using data from the Hubble observing programme #10393 (PI: K. Noll).

A tall, thin structure of dark gas clouds. It is darker and broader at the base and broadens out again at the top, with spikes, fingers and wisps of gas protruding in all directions from its head. Some parts are illuminated, but most is dark, lit only at the edges from behind. A wall of colourful gas lies behind it, bluish at the top and redder towards the bottom. Several blue and gold stars are scattered across it. — This towering structure of billowing gas and dark, obscuring dust might only be a small portion of the Eagle Nebula, but it is no less majestic in appearance for it. 9.5 light-years tall and 7000 light-years distant from Earth, this dusty sculpture is refreshed with the use of new processing techniques. The new Hubble image is part of ESA/Hubble’s 35th anniversary celebrations.
The cosmic cloud shown here is made of cold hydrogen gas, like the rest of the Eagle Nebula. In such regions of space new stars are born among the collapsing clouds. Hot, energetic and formed in great numbers, the stars unleash an onslaught of ultraviolet light and stellar winds that sculpt the gas clouds around them. This produces fantastical shapes like the narrow pillar with blossoming head that we see here. The material in the pillar is thick and opaque to light; it is highlighted at its edges by the glow of more distant gas behind it. The blue colours of the background are dominated by emission from ionised oxygen; the red colours lower down, glowing hydrogen. Orange colours indicate starlight that has managed to break through the dust: bluer wavelengths are blocked more easily by dust, leaving the redder light to pass through.
The stars responsible for carving this particular structure out of the stellar raw material lie just out of view, at the Eagle Nebula’s centre. As the pressure of their intense radiation batters and compresses the gas in this tower of clouds, it’s possible that further star formation is being ignited within. While the starry pillar has withstood these forces well so far, cutting an impressive shape against the background, eventually it will be totally eroded by the multitude of new stars that form in the Eagle Nebula.
Credit: ESA/Hubble & NASA, K. Noll

Press release from ESA Hubble.

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Astronomy

Hubble provides a new view of a galactic favourite, Sombrero Galaxy, or Messier 104

By ScientifiCult 16 April 2025

Hubble provides a new view of a galactic favourite, Sombrero Galaxy, or Messier 104

In anticipation of the upcoming 35th anniversary of the NASA/ESA Hubble Space Telescope, ESA/Hubble is continuing the celebrations with a new image of the Sombrero Galaxy, also known as Messier 104. An eye-catching target for Hubble and a favourite of amateur astronomers, the enigmatic Sombrero Galaxy has features of both spiral and elliptical galaxies. This image incorporates new processing techniques that highlight the unique structure of this galaxy.

As part of ESA/Hubble’s 35th anniversary celebrations, a new image series is being shared to revisit stunning Hubble targets that were previously released. First, a new image of NGC 346 was published. Now, ESA/Hubble is revisiting a fan-favourite galaxy with new image processing techniques. The new image reveals finer detail in the galaxy’s disc, as well as more background stars and galaxies.

Several Hubble images of the Sombrero Galaxy have been released over the past two decades, including this well-known Hubble image from October 2003. In November 2024, the NASA/ESA/CSA James Webb Space Telescope also gave an entirely new perspective on this striking galaxy.

Located around 30 million light-years away in the constellation Virgo, the Sombrero Galaxy is instantly recognisable. Viewed nearly edge on, the galaxy’s softly luminous bulge and sharply outlined disc resemble the rounded crown and broad brim of the Mexican hat from which the galaxy gets its name.

Though the Sombrero Galaxy is packed with stars, it’s surprisingly not a hotbed of star formation. Less than one solar mass of gas is converted into stars within the knotted, dusty disc of the galaxy each year. Even the galaxy’s central supermassive black hole, which at 9 billion solar masses is more than 2000 times more massive than the Milky Way’s central black hole, is fairly calm.

The galaxy is too faint to be spotted with unaided vision, but it is readily viewable with a modest amateur telescope. Seen from Earth, the galaxy spans a distance equivalent to roughly one third of the diameter of the full Moon. The galaxy’s size on the sky is too large to fit within Hubble’s narrow field of view, so this image is actually a mosaic of several images stitched together.

One of the things that makes this galaxy especially notable is its viewing angle, which is inclined just six degrees off of the galaxy’s equator. From this vantage point, intricate clumps and strands of dust stand out against the brilliant white galactic nucleus and bulge, creating an effect not unlike Saturn and its rings — but on an epic galactic scale.

At the same time, this extreme angle makes it difficult to discern the structure of the Sombrero Galaxy. It’s not clear whether it’s a spiral galaxy, like our own Milky Way, or an elliptical galaxy. Curiously, the galaxy’s disc seems like a fairly typical disc for a spiral galaxy, and its spheroidal bulge and halo seem fairly typical for an elliptical galaxy — but the combination of the two components resembles neither a spiral nor an elliptical galaxy.

Researchers have used Hubble to investigate the Sombrero Galaxy, measuring the amount of metals (what astronomers call elements heavier than helium) in stars in the galaxy’s expansive halo. This type of measurement can illuminate a galaxy’s history, potentially revealing whether it has merged with other galaxies in the past. In the case of the Sombrero Galaxy, extremely metal-rich stars in the halo point to a possible merger with a massive galaxy several billion years ago. An ancient galactic clash, hinted at by Hubble’s sensitive measurements, could explain the Sombrero Galaxy’s distinctive appearance.

This image was developed using data from the Hubble observing programme #9714 (PI: K. Noll)

The Sombrero Galaxy is an oblong, pale white disc with a glowing core. It appears nearly edge-on but is slanted slightly in the front, presenting a slightly top-down view of the inner region of the galaxy and its bright core. The outer disc is darker with shades of brown and black. Different coloured distant galaxies and various stars are speckled among the black background of space surrounding the galaxy. — Located around 30 million light-years away in the constellation Virgo, the Sombrero Galaxy is instantly recognisable. Viewed nearly edge on, the galaxy’s softly luminous bulge and sharply outlined disc resemble the rounded crown and broad brim of the Mexican hat from which the galaxy gets its name.
Though the Sombrero Galaxy is packed with stars, it’s surprisingly not a hotbed of star formation. Less than one solar mass of gas is converted into stars within the knotted, dusty disc of the galaxy each year. Even the galaxy’s central supermassive black hole, which at 9 billion solar masses is more than 2000 times more massive than the Milky Way’s central black hole, is fairly calm.
The galaxy is too faint to be spotted with unaided vision, but it is readily viewable with a modest amateur telescope. Seen from Earth, the galaxy spans a distance equivalent to roughly one third of the diameter of the full Moon. The galaxy’s size on the sky is too large to fit within Hubble’s narrow field of view, so this image is actually a mosaic of several images stitched together.
Credit: ESA/Hubble & NASA, K. Noll

Press release from ESA Hubble.

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Hubble investigates SGR 0501+4516 and the magnetar’s birthplace

By ScientifiCult 15 April 2025

Hubble investigates SGR 0501+4516 and the magnetar’s birthplace

Magnetars are ultra-dense stellar remnants with extremely strong magnetic fields. Researchers using the NASA/ESA Hubble Space Telescope have discovered that the magnetar SGR 0501+4516 was not born in a neighbouring supernova as previously thought. The birthplace of this object is now unknown, and SGR 0501+4516 is the likeliest candidate in our galaxy for a magnetar that was not born in a supernova. This discovery was made possible by Hubble’s sensitive instruments as well as precise benchmarks from ESA’s Gaia spacecraft.

In 2008, NASA’s Swift Observatory spotted brief, intense flashes of gamma rays from the outskirts of the Milky Way. The source, an object named SGR 0501+4516, is one of only about 30 known magnetars in the Milky Way.

A magnetar is a special type of neutron star. Neutron stars are some of the most extreme objects in the Universe. These stars typically pack more than the mass of the Sun into a sphere of neutrons about 20 kilometres across. Unsurprisingly, these exotic objects can display several extreme behaviours, such as X-ray and gamma-ray outbursts, intense magnetic fields and rapid rotation.

“Magnetars are neutron stars — the dead remnants of stars, composed entirely of neutrons. They’re so heavy and dense that the electrons and protons which make up atoms have been crushed together into neutrons. What makes magnetars unique is their extreme magnetic fields, billions of times stronger than the strongest magnets we have on Earth,”

said Ashley Chrimes, lead author of the discovery paper published today in the journal Astronomy & Astrophysics. Chrimes is a European Space Agency Research Fellow at the European Space Research and Technology Centre (ESTEC) in the Netherlands.

Most neutron stars are thought to be born in core-collapse supernovae. These spectacular cosmic explosions happen when stars far more massive than the Sun run out of fuel for nuclear fusion. The star’s outer layers fall inward and rebound off the collapsed core in an explosion that can briefly outshine an entire galaxy.

Because magnetars are themselves neutron stars, the natural explanation for their formation is that they too are born in supernovae. This appeared to be the case for SGR 0501+4516, which is located promisingly close to a supernova remnant called HB9. The separation between the magnetar and the center of the supernova remnant on the sky is just 80 arcminutes, or slightly wider than your pinky finger when viewed at the end of your outstretched arm.

But a decade-long study with Hubble cast doubt on the magnetar’s birthplace. After initial observations with ground-based telescopes shortly after SGR 0501+4516’s discovery, researchers leveraged Hubble’s exquisite sensitivity and steady pointing to spot the magnetar’s faint infrared glow in 2010, 2012 and 2020. Each of these images was aligned to a reference frame defined by observations from the European Space Agency’s Gaia spacecraft, which has crafted an extraordinarily precise three-dimensional map of nearly two billion stars in the Milky Way. This method revealed the subtle motion of the magnetar as it inched across the sky. This work therefore demonstrates that Hubble and ESA’s Gaia can reveal mysteries never seen before when joining forces.

“All of this movement we measure is smaller than a single pixel of a Hubble image,” said co-investigator Joe Lyman of the University of Warwick, United Kingdom. “Being able to robustly perform such measurements really is a testament to the long-term stability of Hubble.”

By tracking the magnetar’s position, the team was able to measure the object’s apparent motion across the sky. Both the speed and direction of SGR 0501+4516’s movement showed that the magnetar could not be associated with the nearby supernova remnant. Tracing the magnetar’s trajectory thousands of years into the past showed that there were no other supernova remnants or massive star clusters that it could be associated with.

If SGR 0501+4516 was not born in supernova remnant HB9, the magnetar must either be far older than its reported 20 000-year age, or it must have formed in another way. Magnetars may also be able to form through the merger of two lower-mass neutron stars or through a process called accretion-induced collapse. Accretion-induced collapse requires a binary star system containing a white dwarf: the crystallised core of a dead Sun-like star. If the white dwarf ensnares gas from its companion, it can grow too massive to support itself, leading to an explosion — or possibly the creation of a magnetar.

“Normally, this scenario leads to the ignition of nuclear reactions, and the white dwarf exploding, leaving nothing behind. But it has been theorised that under certain conditions, the white dwarf can instead collapse into a neutron star. We think this might be how SGR 0501 was born,” added Andrew Levan of Radboud University in the Netherlands and the University of Warwick in the United Kingdom.

SGR 0501+4516 is currently the best candidate for a magnetar in our galaxy that may have formed through a merger or accretion-induced collapse. Magnetars that form through accretion-induced collapse could provide an explanation for some of the mysterious cosmic signals called fast radio bursts, which are brief but powerful flashes of radio waves. In particular, this scenario may explain the origin of fast radio bursts that emerge from stellar populations too ancient to have recently birthed stars massive enough to explode as supernovae.

“Magnetar birth rates and formation scenarios are among the most pressing questions in high-energy astrophysics, with implications for many of the Universe’s most powerful transient events, such as gamma-ray bursts, superluminous supernovae, and fast radio bursts,” said Nanda Rea of the Institute of Space Sciences in Barcelona, Spain.

The research team has further Hubble observations planned to study the origins of other magnetars in the Milky Way, helping to understand how these extreme objects form.

At the centre of the image, there is a very bright white-blueish ball, representing the neutron star, with white/blue filaments streaming out from its polar regions, representing magnetic field lines. Some filaments loop around the centre ball, connecting the magnetic north pole to the south. Two blueish beams stream out the two opposite poles towards space. The deep blue background depicting deep space is dotted with small bright-white spots symbolising stars. — This is an artist’s impression of a magnetar, which is a special type of neutron star. Neutron stars are some of the most extreme objects in the Universe. These stars typically pack more than the mass of the Sun into a sphere of neutrons about 20 kilometres across. Unsurprisingly, these exotic objects can display several extreme behaviours, such as X-ray and gamma-ray outbursts, intense magnetic fields and rapid rotation. Magnetars are a specific type of neutron star that are distinguished by their exceptionally strong magnetic fields (which are significantly stronger than those of typical neutron stars).
Researchers using the NASA/ESA Hubble Space Telescope have discovered that the magnetar SGR 0501+4516 was not born in a neighbouring supernova as previously thought. The birthplace of this object is now unknown, and SGR 0501+4516 is the likeliest candidate in our galaxy for a magnetar that was not born in a supernova. It is one of only about 30 known magnetars in the Milky Way.
Credit: ESA

Bibliographic information:

The infrared counterpart and proper motion of magnetar SGR 0501+4516, Astronomy & Astrophysics Volume 696, April 2025 A127, DOI: https://doi.org/10.1051/0004-6361/202453479

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Hubble helps determine Uranus’ rotation rate with unprecedented precision

By ScientifiCult 7 April 2025

Hubble helps determine Uranus’ rotation rate with unprecedented precision

An international team of astronomers using the NASA/ESA Hubble Space Telescope have made new measurements of Uranus’ interior rotation rate with a novel technique, achieving a level of accuracy 1000 times greater than previous estimates. By analysing more than a decade of Hubble observations of Uranus’ aurorae, researchers have refined the planet’s rotation period and established a crucial new reference point for future planetary research.

This visual shows three panels that each show Uranus and dynamic aurora activity. The images were captured in October 2022 on the 8th, 10, and 24th respectively. Each image shows a centred planet with a strong blue hue and a visible white region. A faint ring is also visible around the planet in each image. Each image shows fuzzy blue/purple regions hovering over the planet in different locations to indicate the aurorae. — This visual showcases 3 images from the NASA/ESA Hubble Space Telescope of the dynamic aurora on Uranus in October 2022. These observations were made by the Space Telescope Imaging Spectrograph (STIS) and includes both visible and ultraviolet data. An international team of astronomers used Hubble to make new measurements of Uranus’ interior rotation rate by analysing more than a decade of the telescope’s observations of Uranus’ aurorae. This refinement of the planet’s rotation period achieved a level of accuracy 1000 times greater than previous estimates and serves as a crucial new reference point for future planetary research. Credit: ESA/Hubble, NASA, L. Lamy, L. Sromovsky

Determining a planet’s interior rotation rate is challenging, particularly for a world like Uranus, where direct measurements are not possible. A team led by Laurent Lamy (of LIRA, Observatoire de Paris-PSL and LAM, Aix-Marseille University, France), developed an innovative method to track the rotational motion of Uranus’ aurorae: spectacular light displays generated in the upper atmosphere by the influx of energetic particles near the planet’s magnetic poles. This technique revealed that Uranus completes a full rotation in 17 hours, 14 minutes, and 52 seconds — 28 seconds longer than the estimate obtained by NASA’s Voyager 2 during its 1986 flyby.

“Our measurement not only provides an essential reference for the planetary science community but also resolves a long-standing issue: previous coordinate systems based on outdated rotation periods quickly became inaccurate, making it impossible to track Uranus’ magnetic poles over time,” explains Lamy. “With this new longitude system, we can now compare auroral observations spanning nearly 40 years and even plan for the upcoming Uranus mission.”

This breakthrough was made possible thanks to Hubble’s long-term monitoring of Uranus. Over more than a decade, Hubble has regularly observed its ultraviolet auroral emissions, enabling researchers to track the position of the magnetic poles with magnetic field models.

“The continuous observations from Hubble were crucial,” says Lamy. “Without this wealth of data, it would have been impossible to detect the periodic signal with the level of accuracy we achieved.”

Unlike the aurorae of Earth, Jupiter, or Saturn, Uranus’ aurorae behave in a unique and unpredictable manner. This is due to the planet’s highly tilted magnetic field, which is significantly offset from its rotational axis. The findings not only help astronomers understand Uranus’ magnetosphere but also provide vital information for future missions.

The Planetary Science Decadal Survey in the US prioritized the Uranus Orbiter and Probe concept for future exploration.

These findings set the stage for further studies that will deepen our understanding of one of the most mysterious planets in the Solar System. With its ability to monitor celestial bodies over decades, the Hubble Space Telescope continues to be an indispensable tool for planetary science, paving the way for the next era of exploration at Uranus.

This Hubble image shows Uranus and dynamic aurora activity on 10 October 2022. The centered planet is dominated by a blue hue and a large white region in the lower left. A faint ring is also visible around the planet. Fuzzy blue/purple regions hovering over the planet on the left and ride indicate the presence of aurorae. — This image of Uranus’ aurorae was taken by the NASA/ESA Hubble Space Telescope on 10 October 2022. These observations were made by the Space Telescope Imaging Spectrograph (STIS) and includes both visible and ultraviolet data. An international team of astronomers used Hubble to make new measurements of Uranus’ interior rotation rate by analysing more than a decade of the telescope’s observations of Uranus’ aurorae. This refinement of the planet’s rotation period achieved a level of accuracy 1000 times greater than previous estimates and serves as a crucial new reference point for future planetary research. Credit: ESA/Hubble, NASA, L. Lamy, L. Sromovsky

These results are based on observations acquired with Hubble programmes GO #12601, 13012, 14036, 16313 and DDT #15380 (PI: L. Lamy). The team’s paper has been published today in Nature Astronomy.

Bibliographic information:

Lamy, L., Prangé, R., Berthier, J. et al. A new rotation period and longitude system for Uranus. Nat Astron (2025), DOI: https://doi.org/10.1038/s41550-025-02492-z

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Hubble spots stellar sculptors at work in a nearby galaxy: a new image of the star cluster NGC 346

By ScientifiCult 4 April 2025

Hubble spots stellar sculptors at work in a nearby galaxy: a new image of the star cluster NGC 346

In anticipation of the upcoming 35th anniversary of the NASA/ESA Hubble Space Telescope, ESA/Hubble is kicking off the celebrations with a new image of the star cluster NGC 346, featuring new data and processing techniques. This prolific star factory is in the Small Magellanic Cloud, one of the largest of the Milky Way’s satellite galaxies.

As part of ESA/Hubble’s 35th anniversary celebrations, a new image series is being shared to revisit stunning Hubble targets that were previously released. This image series combines new processing techniques with the latest data from Hubble to re-release these cosmic scenes for the public to enjoy.

This new image showcases the dazzling young star cluster NGC 346. Although several images of NGC 346 have been released previously, this view includes new data and is the first to combine Hubble observations made at infrared, optical, and ultraviolet wavelengths into an intricately detailed view of this vibrant star-forming factory.

NGC 346 is located in the Small Magellanic Cloud, a satellite galaxy of the Milky Way that lies 200 000 light-years away in the constellation Tucana. The Small Magellanic Cloud is less rich in elements heavier than helium — what astronomers call metals — than the Milky Way. This makes conditions in the galaxy similar to what existed in the early universe.

NGC 346 is home to more than 2500 newborn stars. The cluster’s most massive stars, which are many times more massive than our Sun, blaze with an intense blue light in this image. The glowing pink nebula and snakelike dark clouds are sculpted by the luminous stars in the cluster.

Hubble’s exquisite sensitivity and resolution were instrumental in uncovering the secrets of NGC 346’s star formation. Using two sets of observations taken 11 years apart, researchers traced the motions of NGC 346’s stars, revealing them to be spiralling in toward the centre of the cluster. This spiralling motion arises from a stream of gas from the outside of the cluster that fuels star formation in the centre of the turbulent cloud.

The inhabitants of this cluster are stellar sculptors, carving out a bubble from the nebula. NGC 346’s hot, massive stars produce intense radiation and fierce stellar winds that pummel the billowing gas of their birthplace and begin to disperse the surrounding nebula.

The nebula, named N66, is the brightest example of an H II (pronounced ‘H-two’) region in the Small Magellanic Cloud. H II regions are set aglow by ultraviolet light from hot young stars like those in NGC 346. The presence of the brilliant nebula indicates the young age of the star cluster, as an H II region shines only as long as the stars that power it — a mere few million years for the massive stars pictured here.

This image was developed from multiple Hubble observing programmes: #10248 (PI: Antonella Nota), #12940 (PI: Phillip Massey), #13680 (PI: Elena Sabbi), #15891 (PI: Claire Murray), and #17118 (PI: Claire Murray).

A star cluster within a nebula. The background is filled with thin, pale blue clouds. Parts are thicker and pinker in colour. The cluster is made up of bright blue stars that illuminate the nebula around them. Large arcs of dense dust curve around, before and behind the clustered stars, pressed together by the stars’ radiation. Behind the clouds of the nebula can be seen large numbers of orange stars. — The Hubble Space Telescope spots stellar sculptors at work in a nearby galaxy: a new image of the star cluster NGC 346. This new image showcases NGC 346, a dazzling young star cluster in the Small Magellanic Cloud. The Small Magellanic Cloud is a satellite galaxy of the Milky Way, located 200 000 light-years away in the constellation Tucana. The Small Magellanic Cloud is less rich in elements heavier than helium — what astronomers call metals — than the Milky Way. This makes conditions in the galaxy similar to what existed in the early universe. Although several images of NGC 346 have been released previously, this view includes new data and is the first to combine Hubble observations made at infrared, optical, and ultraviolet wavelengths into an intricately detailed view of this vibrant star-forming factory. NGC 346 is home to more than 2500 newborn stars. The cluster’s most massive stars, which are many times more massive than our Sun, blaze with an intense blue light in this image. The glowing pink nebula and snakelike dark clouds are the remnant of the birthsite of the stars in the cluster. The inhabitants of this cluster are stellar sculptors, carving out a bubble from the nebula. NGC 346’s hot, massive stars produce intense radiation and fierce stellar winds that pummel the billowing gas of their birthplace and begin to disperse the surrounding nebula. The nebula, named N66, is the brightest example of an H II (pronounced ‘H-two’) region in the Small Magellanic Cloud. H II regions are set aglow by ultraviolet light from hot young stars like those in NGC 346. The presence of the brilliant nebula indicates the young age of the star cluster, as an H II region shines only as long as the stars that power it — a mere few million years for the massive stars pictured here. Credit: ESA/Hubble & NASA, A. Nota, P. Massey, E. Sabbi, C. Murray, M. Zamani (ESA/Hubble)

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Webb exposes complex atmosphere of SIMP 0136, a starless super-Jupiter

By ScientifiCult 3 March 2025

Webb exposes complex atmosphere of SIMP 0136, a starless super-Jupiter

An international team of researchers has discovered that previously observed variations in brightness across a free-floating planetary-mass object known as SIMP 0136 must be the result of a complex combination of atmospheric factors, and cannot be explained by clouds alone.

Using the NASA/ESA/CSA James Webb Space Telescope to monitor a broad spectrum of infrared light emitted by SIMP 0136 over two full rotation periods, the team was able to detect variations in cloud layers, temperature, and carbon chemistry that were previously hidden from view. The results provide crucial insight into the three-dimensional complexity of gas giant atmospheres within and beyond our solar system.

Rapidly rotating, free-floating

SIMP 0136 is a rapidly rotating, free-floating object roughly 13 times the mass of Jupiter, located in the Milky Way just 20 light-years from Earth. Although it is not classified as a gas giant exoplanet — it doesn’t orbit a star and may instead be a brown dwarf — SIMP 0136 is an ideal target for exo-meteorology: It is the brightest object of its kind in the northern sky. Because it is isolated, it can be observed directly and with no fear of light contamination or variability caused by a host star. And its short rotation period of just 2.4 hours makes it possible to survey very efficiently.

Prior to the Webb observations, SIMP 0136 had been studied extensively using ground-based observatories, as well as and NASA’s Spitzer Space Telescope and the NASA/ESA Hubble Space Telescope.

“We already knew that it varies in brightness, and we were confident that there are patchy cloud layers that rotate in and out of view and evolve over time,” explained Allison McCarthy, doctoral student at Boston University and lead author on a study published today in The Astrophysical Journal Letters. “We also thought there could be temperature variations, chemical reactions, and possibly some effects of auroral activity affecting the brightness, but we weren’t sure.”

To figure it out, the team needed Webb’s ability to measure very precise changes in brightness over a broad range of wavelengths.

Charting thousands of infrared rainbows

Using NIRSpec (Near-Infrared Spectrograph), Webb captured thousands of individual 0.6- to 5.3-micron spectra — one every 1.8 seconds over more than three hours as the object completed one full rotation. This was immediately followed by an observation with MIRI (Mid-Infrared Instrument), which collected hundreds of measurements of 5- to 14-micron light — one every 19.2 seconds, over another rotation.

The result was hundreds of detailed light curves, each showing the change in brightness of a very precise wavelength (color) as different sides of the object rotated into view.

“To see the full spectrum of this object change over the course of minutes was incredible,” said principal investigator Johanna Vos, from Trinity College Dublin. “Until now, we only had a little slice of the near-infrared spectrum from Hubble, and a few brightness measurements from Spitzer.”

The team noticed almost immediately that there were several distinct light-curve shapes. At any given time, some wavelengths were growing brighter, while others were becoming dimmer or not changing much at all. A number of different factors must be affecting the brightness variations.

“Imagine watching Earth from far away. If you were to look at each color separately, you would see different patterns that tell you something about its surface and atmosphere, even if you couldn’t make out the individual features,” explained co-author Philip Muirhead, also from Boston University. “Blue would increase as oceans rotate into view. Changes in brown and green would tell you something about soil and vegetation.”

Illustration of a gas giant planet or brown dwarf on a background of distant stars. — This artist’s concept shows what the isolated planetary-mass object SIMP 0136 could look like based on recent observations from the NASA/ESA/CSA James Webb Space Telescope.
SIMP 0136 has a mass about 13 times that of Jupiter. Although it is thought to have the structure and composition of a gas giant, it is not technically classified as an exoplanet because it doesn’t orbit its own star.
The colors shown in the illustration represent near-infrared light, which is invisible to human eyes. SIMP 0136 is relatively warm — about 825 degrees Celsius or 1,100 kelvins — but is not hot enough to give off enough visible light to see from Earth, and is not illuminated by a host star. The bluish glow near the poles represents auroral energy (light given off by electrons spiraling in a magnetic field) which has been detected at radio wavelengths.
Researchers used NIRSpec (Near-infrared Spectrograph) and MIRI (Mid-Infrared Instrument) to monitor the brightness of SIMP 0136 over two full rotations in July 2023. By analyzing the change in brightness of different wavelengths over time, researchers were able to detect variability in cloud cover at different depths, temperature variations in the high atmosphere, and changes in carbon chemistry as different sides of the object rotated in and out of view.
SIMP 0136 is located within the Milky Way, about 20 light-years from Earth, in the constellation Pisces. It is the brightest isolated planet or brown dwarf visible from the Northern Hemisphere, and is thought to be about 200 million years old. This illustration is based on spectroscopic observations. Webb has not captured a direct image of the object.
Credit: NASA, ESA, CSA, J. Olmsted (STScI)

Patchy clouds, hot spots, and carbon chemistry

To figure out what could be causing the variability on SIMP 0136, the team used atmospheric models to show where in the atmosphere each wavelength of light was originating.

“Different wavelengths provide information about different depths in the atmosphere,” explained McCarthy. “We started to realize that the wavelengths that had the most similar light-curve shapes also probed the same depths, which reinforced this idea that they must be caused by the same mechanism.”

One group of wavelengths, for example, originates deep in the atmosphere where there could be patchy clouds made of iron particles. A second group comes from higher clouds thought to be made of tiny grains of silicate minerals. The variations in both of these light curves are related to patchiness of the cloud layers.

A third group of wavelengths originates at very high altitude, far above the clouds, and seems to track temperature. Bright “hot spots” could be related to auroras that were previously detected at radio wavelengths, or to upwelling of hot gas from deeper in the atmosphere.

Some of the light curves cannot be explained by either clouds or temperature, but instead show variations related to atmospheric carbon chemistry. There could be pockets of carbon monoxide and carbon dioxide rotating in and out of view, or chemical reactions causing the atmosphere to change.

“We haven’t really figured out the chemistry part of the puzzle yet,” said Vos. “But these results are really exciting because they are showing us that the abundances of molecules like methane and carbon dioxide could change from place to place and over time. If we are looking at an exoplanet and can get only one measurement, we need to consider that it might not be representative of the entire planet.”

This research was conducted as part of Webb’s General Observer (GO) Program 3548.

Bibliographic information:

Allison M. McCarthy et al 2025, ApJL 981 L22, DOI: 10.3847/2041-8213/ad9eaf

The graphic has two parts. On the left are light curves showing the change in brightness of three sets of near-infrared wavelengths over time. On the right is a cross-section of the object’s atmosphere, showing the altitude that each set of wavelengths originates and their relationship to cloud layers or temperature. — These light curves show the change in brightness of three different sets of wavelengths (colors) of near-infrared light coming from the isolated planetary-mass object SIMP 0136 as it rotated. The light was captured by Webb’s NIRSpec (Near-Infrared Spectrograph), which collected a total of 5,726 spectra — one every 1.8 seconds — over the course of about 3 hours on 23 July 2023 (SIMP 0136 completes one rotation every 2.4 hours).
By comparing these light curves to models, researchers were able to show that each set of wavelengths probes different depths (pressures) in the atmosphere.
The curve shown in red tracks the brightness of 0.9- to 1.4-micron light thought to originate deep in the atmosphere at a pressure of about 10 bars (about 10 times the air pressure at sea level on Earth), within clouds made of iron particles. The curve shown in yellow tracks the brightness of 1.4- to 2.3-micron light from a pressure of about 1 bar within higher clouds made of tiny grains of silicate minerals. The variations in brightness shown by these two curves is related to patchiness of the cloud layers, which emit some wavelengths of light and absorb others.
The curve shown in blue tracks the brightness of 3.3- to 3.6-micron light that originates high above the clouds at a pressure of about 0.1 bars. Changes in brightness of these wavelengths are related to variations in temperature around the object. Bright “hot spots” could be related to auroras that have been detected at radio wavelengths, or to upwelling of hot gas from deeper in the atmosphere.
The differences in shape of these three light curves show that there are complex variations in SIMP 0136’s atmosphere with depth as well as longitude. If the atmosphere varied around the object in the same way at all depths, the light curves would have similar patterns. If it varied with depth, but not longitude, the light curves would be straight, flat lines.
Note this graph shows the relative change in brightness for each given set of wavelengths over time, not the difference in absolute brightness between the different sets. At any given time, there is more light coming from the deep atmosphere (red light curve) than from the upper atmosphere (blue light curve).
SIMP 0136 is located within the Milky Way, about 20 light-years from Earth, in the constellation Pisces. It is the brightest isolated planet or brown dwarf visible from the Northern Hemisphere, and is thought to be about 200 million years old. The artist’s concepts are based on spectroscopic observations. Webb has not captured a direct image of the object.
Credit: NASA, ESA, CSA, J. Olmsted (STScI)

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Hubble traces hidden history of the Andromeda Galaxy

By ScientifiCult 16 January 2025

Hubble traces hidden history of the Andromeda Galaxy

Panorama of nearest galaxy unveils hundreds of millions of stars

The largest photomosaic of the Andromeda galaxy, assembled from NASA/ESA Hubble Space Telescope observations, has been unveiled. It took more than 10 years to collect data for this colorful portrait of our neighboring galaxy and was created from more than 600 snapshots. This stunning, colorful mosaic captures the glow of 200 million stars, and is spread across roughly 2.5 billion pixels.

In the years following the launch of the NASA/ESA Hubble Space Telescope, astronomers have tallied over 1 trillion galaxies in the universe. But only one galaxy stands out as the most important nearby stellar island to our Milky Way: the magnificent Andromeda galaxy (Messier 31). It can be seen with the naked eye on a very clear autumn night as a faint cigar-shaped object roughly the apparent angular diameter of our Moon.

A century ago, Edwin Hubble first established that this so-called “spiral nebula” was actually far outside our own Milky Way galaxy — at a distance of approximately 2.5 million light-years, or roughly 25 Milky Way diameters. Prior to that, astronomers had long thought that the Milky Way encompassed the entire universe. Overnight, Hubble’s discovery turned cosmology upside down by unveiling an infinitely grander universe.

Now, a century later, the space telescope named for Hubble has accomplished the most comprehensive survey of this enticing empire of stars. The Hubble telescope is yielding new clues to the evolutionary history of Andromeda, and it looks markedly different from the Milky Way’s history.

Without Andromeda as a proxy for spiral galaxies in the universe at large, astronomers would know much less about the structure and evolution of our own Milky Way. That’s because we are embedded inside the Milky Way.

Hubble’s sharp imaging capabilities can resolve more than 200 million stars in the Andromeda galaxy, detecting only stars brighter than our Sun. They look like grains of sand across the beach. But that’s just the tip of the iceberg. Andromeda’s total population is estimated to be 1 trillion stars, with many less massive stars falling below Hubble’s sensitivity limit.

Photographing Andromeda was a herculean task because the galaxy is a much bigger target on the sky than the galaxies Hubble routinely observes, which are often billions of light-years away. The full mosaic was carried out under two Hubble observing programs. In total it required over 1,000 Hubble orbits, spanning more than a decade.

The Andromeda galaxy is shown at the top of the visual. It is a spiral galaxy that spreads across the image. It is tilted nearly edge-on to our line of sight so that it appears very oval. The borders of the galaxy are jagged because the image is a mosaic of smaller, square images against a black background. The outer edges of the galaxy are blue, while the inner two-thirds is yellowish with a bright, central core. Five callout squares highlight interesting features of the galaxy — This is the largest photomosaic ever made by the Hubble Space Telescope. The target is the vast Andromeda galaxy that is only 2.5 million light-years from Earth, making it the nearest galaxy to our own Milky Way. Andromeda is seen almost edge-on, tilted by 77 degrees relative to Earth’s view. The galaxy is so large that the mosaic is assembled from approximately 600 separate fields of view taken over 10 years of Hubble observing. The mosaic image is made up of at least 2.5 billion pixels. Hubble resolves an estimated 200 million stars that are hotter than our sun, but still a fraction of the galaxy’s total estimated stellar population.
Interesting regions include:
Clusters of bright blue stars embedded within the galaxy, background galaxies seen much farther away, and photo-bombing by a couple bright foreground stars that are actually inside our Milky Way;
NGC 206 the most conspicuous star cloud in Andromeda;
A young cluster of blue newborn stars;
The satellite galaxy M32, that may be the residual core of a galaxy that once collided with Andromeda;
Dark dust lanes across myriad stars.
Credit: NASA, ESA, B. Williams (U. of Washington)

This panorama started with the Panchromatic Hubble Andromeda Treasury (PHAT) program about a decade ago. Images were obtained at near-ultraviolet, visible, and near-infrared wavelengths using the Advanced Camera for Surveys and the Wide Field Camera aboard Hubble to photograph the northern half of Andromeda.

This program was followed up by the Panchromatic Hubble Andromeda Southern Treasury (PHAST), which added images of approximately 100 million stars in the southern half of Andromeda. This region is structurally unique and more sensitive to the galaxy’s merger history than the northern disk mapped by the PHAT survey.

The combined programs collectively cover the entire disk of Andromeda, which is seen almost edge-on — tilted by 77 degrees relative to Earth’s view. The galaxy is so large that the mosaic is assembled from approximately 600 separate fields of view. The mosaic image is made up of at least 2.5 billion pixels.

The complementary Hubble survey programs provide information about the age, heavy-element abundance and stellar masses inside Andromeda. This will allow astronomers to distinguish between competing scenarios where Andromeda merged with one or more galaxies. Hubble’s detailed measurements constrain models of Andromeda’s merger history and disk evolution.

Though the Milky Way and Andromeda formed presumably around the same time many billions of years ago, observational evidence shows that they have very different evolutionary histories, despite growing up in the same cosmological neighborhood. Andromeda seems to be more highly populated with younger stars and unusual features like coherent streams of stars, say researchers. This implies it has a more active recent star-formation and interaction history than the Milky Way.

A possible culprit is the compact satellite galaxy Messier 32, which resembles the stripped-down core of a once-spiral galaxy that may have interacted with Andromeda in the past. Computer simulations suggest that when a close encounter with another galaxy uses up all the available interstellar gas, star formation subsides.

Hubble’s new findings will support future observations by the NASA/ESA/CSA James Webb Space Telescope.

The Andromeda galaxy, a spiral galaxy, spreads across the image. It is tilted nearly edge-on to our line of sight so that it appears very oval. The borders of the galaxy are jagged because the image is a mosaic of smaller, square images against a black background. The outer edges of the galaxy are blue, while the inner two-thirds is yellowish with a bright, central core. Dark, dusty filamentary clouds wrap around the outer half of the galaxy’s disk. At 10 o’clock, a smaller dwarf elliptical galaxy forms a fuzzy, yellow blob. Hubble’s sharp vision distinguishes about 200 million stars within the image. — This the largest photomosaic ever assembled from NASA/ESA Hubble Space Telescope observations: it is a panoramic view of the neighboring Andromeda galaxy, located 2.5 million light-years away. It took over 10 years to make this vast and colorful portrait of the galaxy, requiring over 600 Hubble snapshots. The galaxy is so close to us, that in angular size it is six times the apparent diameter of the full Moon, and can be seen with the unaided eye. For Hubble’s pinpoint view, that’s a lot of celestial real estate to cover. This stunning, colorful mosaic captures the glow of 200 million stars. That’s still a fraction of Andromeda’s population. And the stars are spread across about 2.5 billion pixels. The detailed look at the resolved stars will help astronomers piece together the galaxy’s past history that includes mergers with smaller satellite galaxies.
Credit: NASA, ESA, B. Williams (University of Washington)

Press release from ESA Hubble

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By observing NGC 346, Webb finds planet-forming discs lived longer in early Universe

By ScientifiCult 16 December 2024

By observing NGC 346, Webb finds planet-forming discs lived longer in early Universe: new data refutes current theories of planet formation in Universe’s early days

The NASA/ESA/CSA James Webb Space Telescope just solved a conundrum by proving a controversial finding made with the NASA/ESA Hubble Space Telescope more than 20 years ago.

This image features NGC 346, one of the most dynamic star-forming regions in nearby galaxies, as seen by the NASA/ESA/CSA James Webb Space Telescope.
NCG 346 is located in the Small Magellanic Cloud (SMC), a dwarf galaxy close to our Milky Way.
Credit: NASA, ESA, CSA, STScI, A. Pagan (STScI)

In 2003, Hubble provided evidence of a massive planet around a very old star, almost as old as the Universe. Such stars possess only small amounts of heavier elements that are the building blocks of planets. This implied that some planet formation happened when our Universe was very young, and those planets had time to form and grow big inside their primordial discs, even bigger than Jupiter. But how? This was puzzling.

A side-by-side comparison of a Hubble image of the massive star cluster NGC 346 (left) versus a Webb image of the same cluster (right). The Hubble image shows the cluster in shades of blue against a black background punctuated by white stars of various sizes. Ethereal nebulosity, looking much like draped chiffon, dominates the image. The Webb view, in shades of pink and orange against a black background, is speckled with fewer stars than in the Hubble version. These stars are white and pink. Webb pierces through the cluster’s clouds to reveal more of its structure, which looks like twisted fibers. — This side-by-side comparison shows a Hubble image of the massive star cluster NGC 346 (left) versus a Webb image of the same cluster (right). While the Hubble image shows more nebulosity, the Webb image pierces through those clouds to reveal more of the cluster’s structure. NGC 346 has a relative lack of elements heavier than helium and hydrogen, making it a good proxy for stellar environments in the early, distant universe.
Credit: NASA, ESA, CSA, STScI, O. C. Jones (UK ATC), G. De Marchi (ESTEC), M. Meixner (USRA), A. Nota (ESA)

To answer this question, researchers used Webb to study stars in a nearby galaxy that, much like the early Universe, lacks large amounts of heavy elements. They found that not only do some stars there have planet-forming discs, but that those discs are longer-lived than those seen around young stars in our Milky Way galaxy.

“With Webb, we have a really strong confirmation of what we saw with Hubble, and we must rethink how we model planet formation and early evolution in the young Universe,” said study leader Guido De Marchi of ESA’s European Space Research and Technology Centre in Noordwijk, Netherlands.

A different environment in early times

In the early Universe, stars formed from mostly hydrogen and helium, and very few heavier elements such as carbon and iron, which came later through supernova explosions.

“Current models predict that with so few heavier elements, the discs around stars have a short lifetime, so short in fact that planets cannot grow big,” said the Webb study’s co-investigator Elena Sabbi, chief scientist for Gemini Observatory at the National Science Foundation’s NOIRLab in Tucson. “But Hubble did see those planets, so what if the models were not correct and discs could live longer?”

To test this idea, scientists trained Webb on the Small Magellanic Cloud, a dwarf galaxy that is one of the Milky Way’s nearest neighbors. In particular, they examined the massive, star-forming cluster NGC 346, which also has a relative lack of heavier elements. The cluster served as a nearby proxy for studying stellar environments with similar conditions in the early, distant Universe.

The center of the image contains arcs of orange and pink that form a boat-like shape. One end of these arcs points to the top right of the image, while the other end point toward the bottom left. Another plume of orange and pink expands from the center to the top left of the image. To the right of this plume is a large cluster of white stars. There are various other white stars and a few galaxies of different sizes spread throughout the image. Ten, small, yellow circles overlaid at various points across the image indicate the positions of the ten stars surveyed in this study. — This is a NASA/ESA/CSA James Webb Space Telescope image of NGC 346, a massive star cluster in the Small Magellanic Cloud, a dwarf galaxy that is one of the Milky Way’s nearest neighbors. With its relative lack of elements heavier than helium and hydrogen, the NGC 346 cluster serves as a nearby proxy for studying stellar environments with similar conditions in the early, distant Universe. Ten, small, yellow circles overlaid on the image indicate the positions of the ten stars surveyed in this study.
Credit: NASA, ESA, CSA, STScI, O. C. Jones (UK ATC), G. De Marchi (ESTEC), M. Meixner (USRA)

Hubble observations of NGC 346 from the mid 2000s revealed many stars about 20 to 30 million years old that seemed to still have planet-forming discs around them. This went against the conventional belief that such discs would dissipate after 2 or 3 million years.

“The Hubble findings were controversial, going against not only empirical evidence in our galaxy but also against the current models,” said De Marchi. “This was intriguing, but without a way to obtain spectra of those stars, we could not really establish whether we were witnessing genuine accretion and the presence of discs, or just some artificial effects.”

Now, thanks to Webb’s sensitivity and resolution, scientists have the first-ever spectra of forming, Sun-like stars and their immediate environments in a nearby galaxy.

“We see that these stars are indeed surrounded by discs and are still in the process of gobbling material, even at the relatively old age of 20 or 30 million years,” said De Marchi. “This also implies that planets have more time to form and grow around these stars than in nearby star-forming regions in our own galaxy.”

By observing NGC 346, Webb finds planet-forming discs lived longer in early Universe: new data refutes current theories of planet formation in Universe’s early days. This image features NGC 346, one of the most dynamic star-forming regions in nearby galaxies, as seen by the NASA/ESA/CSA James Webb Space Telescope.
NCG 346 is located in the Small Magellanic Cloud (SMC), a dwarf galaxy close to our Milky Way.
Credit: NASA, ESA, CSA, STScI, A Pagan (STScI)

A New Way of Thinking

This finding refutes previous theoretical predictions that when there are very few heavier elements in the gas around the disc, the star would very quickly blow away the disc. So the disc’s life would be very short, even less than a million years. But if a disc doesn’t stay around the star long enough for the dust grains to stick together and pebbles to form and become the core of a planet, how can planets form?

The researchers explained that there could be two distinct mechanisms, or even a combination, for planet-forming discs to persist in environments scarce in heavier elements.

First, to be able to blow away the disc, the star applies radiation pressure. For this pressure to be effective, elements heavier than hydrogen and helium would have to reside in the gas. But the massive star cluster NGC 346 only has about ten percent of the heavier elements that are present in the chemical composition of our Sun. Perhaps it simply takes longer for a star in this cluster to disperse its disc.

The second possibility is that, for a Sun-like star to form when there are few heavier elements, it would have to start from a larger cloud of gas. A bigger gas cloud will produce a bigger disc. So there is more mass in the disc and therefore it would take longer to blow the disc away, even if the radiation pressure were working in the same way.

“With more matter around the stars, the accretion lasts for a longer time,” said Sabbi. “The discs take ten times longer to disappear. This has implications for how you form a planet, and the type of system architecture that you can have in these different environments. This is so exciting.”

The science team’s paper appears in the 16 December 2024 issue of The Astrophysical Journal.

planet-forming discs Graphic titled Star in NGC 346, Molecular Hydrogen in Protoplanetary Disk, NIRSpec Microshutter Array Spectroscopy showing brightness of 2.02- to 2.37-micron light of a star and its environment (plotted in yellow) and a star’s environment only (plotted in pink) on an xy graph of brightness versus wavelength in microns. Two wavelength bands, ranging from 2.05 to 2.07 and 2.16 to 2.18, are highlighted in red and labeled Hot Atomic Helium, He. A band from 2.11 to 2.13 in blue is labeled Cold Molecular Hydrogen, H 2. The spectrum of the star plus environment (yellow) has prominent peaks at 2.06 and 2.17 microns (He), and at 2.12 microns (H). The spectrum of the star’s environment only (pink) also has peaks at 2.06 and 2.17 microns (He), but not at 2.12 (H). The two spectra are offset vertically for readability. An inset shows them plotted with the same vertical alignment: the helium peaks on the star plus environment spectrum are slightly taller than those of the environment only. — This graph shows, on the bottom left in yellow, a spectrum of one of the 10 target stars in this study (as well as accompanying light from the immediate background environment). Spectral fingerprints of hot atomic helium, cold molecular hydrogen, and hot atomic hydrogen are highlighted. On the top left in magenta is a spectrum slightly offset from the star that includes only light from the background environment. This second spectrum lacks a spectral line of cold molecular hydrogen.
On the right is the comparison of the top and bottom lines. This comparison shows a large peak in the cold molecular hydrogen coming from the star but not its nebular environment. Also, atomic hydrogen shows a larger peak from the star. This indicates the presence of a protoplanetary disc immediately surrounding the star. The data was taken with the microshutter array on the James Webb Space Telescope’s NIRSpec (Near-Infrared Spectrometer) instrument.
Credit: NASA, ESA, CSA, J. Olmsted (STScI)

Press release from ESA Webb

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Hubble celebrates a decade of tracking the outer planets

By ScientifiCult 9 December 2024

Hubble celebrates a decade of tracking the outer planets

From 2014 to 2024, the NASA/ESA Hubble Space Telescope has been studying the outer planets under a program called OPAL (Outer Planet Atmospheres Legacy) to obtain long-time baseline observations of Jupiter, Saturn, Uranus, and Neptune in order to understand their atmospheric dynamics and evolution. Hubble is the only telescope that can provide high spatial resolution and image stability for global studies of cloud coloration, activity, and atmospheric motion on a consistent time basis to help constrain the underlying mechanics of weather and climate systems.

All four of the outer planets have deep atmospheres and no solid surfaces. Their churning atmospheres have their own unique weather systems, some with colorful bands of multicolored clouds, and with mysterious, large storms that pop up or linger for many years. Each also has seasons lasting many years as they revolve around the Sun.

Following the complex behavior is akin to understanding Earth’s dynamic weather as followed over many years, as well as the Sun’s influence on the solar system’s weather. The four wonder-worlds also serve as proxies for understanding the weather and climate on similar planets orbiting other stars.

Planetary scientists realized that any one year of data from Hubble, while interesting in its own right, doesn’t tell you the full story on the outer planets. Hubble’s OPAL program has routinely visited the planets once a year when they are closest to the Earth, an alignment called opposition. This has yielded a huge archive of data that has led to a string of remarkable discoveries to share with planetary astronomers around the world.

Highlights of the OPAL team’s decade of discovery is provided below.

Jupiter

Jupiter’s bands of clouds present an ever-changing kaleidoscope of shapes and colors. There is always stormy weather on Jupiter: cyclones, anticyclones, wind shear, and the largest storm in the solar system, the Great Red Spot (GRS). Jupiter is covered with largely ammonia ice-crystal clouds on top of an atmosphere that’s tens of thousands of miles deep.

Hubble’s sharp images track clouds and measure the winds, storms, and vortices, in addition to monitoring the size, shape and behavior of the GRS. Hubble follows as the GRS continues shrinking in size, but is still large enough to swallow Earth. OPAL data recently measured how often mysterious dark ovals—visible only at ultraviolet wavelengths—appeared in the “polar hoods” of stratospheric haze. Unlike Earth, Jupiter is only inclined three degrees on its axis (Earth is 23.5 degrees). Seasonal changes might not be expected, except that Jupiter’s distance from the Sun varies by roughly 64 million kilometres over its 12-year-long orbit, and so OPAL closely monitors the atmosphere for seasonal effects. Another Hubble advantage is that ground-based observatories can’t continuously view Jupiter for two Jupiter rotations, because that adds up to 20 hours. During that time, an observatory on the ground would have gone into daytime and Jupiter would no longer be visible until the next evening.

A two-panel image labeled “Jupiter, January 5, 2024, HST WFC3/UVIS” showcases the wealth of information provided by the spectral filters on the Hubble’s Wide Field Camera 3 (WFC3) science instrument. At left, this Hubble image of Jupiter is created using three filters at wavelengths similar to the colors seen by the human eye: F395N is blue, F502N is green, F658N is red. At right, the wavelength bounds are widened beyond the visible range to extend just into the ultraviolet (UV) and infrared regimes: F343N is blue, F467M is green, FQ889N is red. Humans can’t perceive these extended wavelengths. The result is a vivid disk that shows UV-absorbing lofty hazes as orange (over the poles and in three large storms, including the Great Red Spot), and freshely-formed ice as white (compact storm plumes just north of the equator). These filters (and others not shown here) allow astronomers to study differences in cloud thickness, altitude, and chemical makeup. — Two views of Jupiter showcase the wealth of information provided by the spectral filters on the Hubble Space Telescope’s Wide Field Camera 3 (WFC3) science instrument. At left, the RGB composite is created using three filters at wavelengths similar to the colors seen by the human eye. At right, the wavelength bounds are widened beyond the visible range to extend just into the ultraviolet (UV) and infrared regimes. Humans cannot perceive these extended wavelengths, but some animals are able to detect infrared and ultraviolet light. The result is a vivid disk that shows UV-absorbing lofty hazes as orange (over the poles and in three large storms, including the Great Red Spot), and freshly-formed ice as white (compact storm plumes just north of the equator). Astronomers, including the OPAL team, use these filters (and others not shown here) to study differences in cloud thickness, altitude, and chemical makeup.
Credit: NASA, ESA, A. Simon (NASA/GSFC), M. Wong (UC Berkeley), J. DePasquale (STScI)

OPAL’s findings may also support ESA’s Jupiter Icy Moons Explorer, Juice, which was launched on 14 April 2023. Juice will make detailed observations of Jupiter and its three large ocean-bearing moons — Ganymede, Callisto and Europa — with a suite of remote sensing, geophysical and in situ instruments. The mission will characterise these moons as both planetary objects and possible habitats, explore Jupiter’s complex environment in depth, and study the wider Jupiter system as an archetype for gas giants across the Universe.

A nine-panel collage showing Hubble images of Jupiter taken under the OPAL (Outer Planet Atmospheres Legacy) program from 2015-2024, with approximately true color. OPAL tracks the Great Red Spot (GRS) and other notable changes in Jupiter’s banded cloud structure of zones and belts over time.Credit:
NASA, ESA, A. Simon (GSFC), M. Wong (UC Berkeley), J. DePasquale (STScI) — A nine-panel collage showing Hubble images of Jupiter taken under the OPAL (Outer Planet Atmospheres Legacy) program from 2015-2024, with approximately true color. OPAL tracks the Great Red Spot (GRS) and other notable changes in Jupiter’s banded cloud structure of zones and belts over time.
Credit:
NASA, ESA, A. Simon (GSFC), M. Wong (UC Berkeley), J. DePasquale (STScI)

Saturn

Saturn takes more than 29 years to orbit the Sun, and so OPAL has followed it for approximately one quarter of a Saturnian year (picking up in 2018, after the end of the Cassini mission). Because Saturn is tilted 26.7 degrees, it goes through more profound seasonal changes than Jupiter. Saturnian seasons last approximately seven years. This also means Hubble can view the spectacular ring system from an oblique angle of almost 30 degrees to see the rings tilted edge-on. Edge-on, the rings nearly vanish because they are relatively paper-thin. This will happen again in 2025.

OPAL has followed changes in colors of Saturn’s atmosphere. The varying color was first detected by the Cassini orbiter, but Hubble provides a longer baseline. Hubble revealed slight changes from year-to-year in color, possibly caused by cloud height and winds. The observed changes are subtle because OPAL has covered only a fraction of a Saturnian year. Major changes happen when Saturn progresses into the next season.

Saturn’s mysteriously dark ring spokes, which slice across the ring plane, are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly formed spokes continuously add to the pattern. They were first seen in 1981 by Voyager 2. Cassini also saw the spokes during its 13-year-long mission, which ended in 2017. Hubble shows that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021. Long-term monitoring shows that both the number and contrast of the spokes vary with Saturn’s seasons.

A six-panel collage titled “Saturn, August 22, 2024, HST WFC3/UVIS.” This “Warhol-esque” array of Saturn images depict real data from multiple filters mapped onto the RGB colors perceptible to the human eye. Each filter combination emphasizes subtle differences in cloud altitude or composition. Infrared spectra from the Cassini mission suggested that Saturn’s aerosol particles may have even more complex chemical diversity than on Jupiter. The OPAL (Outer Planet Atmospheres Legacy) program extends Cassini’s legacy by measuring how the subtle patterns in the clouds vary over time. — n array of Saturn images depict real data from multiple filters mapped onto the RGB colors perceptible to the human eye. Each filter combination emphasizes the subtle differences in cloud altitude or composition. Infrared spectra from the Cassini mission suggested that Saturn’s aerosol particles may have even more complex chemical diversity than on Jupiter.
Credit: NASA, ESA, A. Simon (NASA/GSFC), M. Wong (UC Berkeley), J. DePasquale (STScI)

Uranus

Uranus is tilted on its side so that its spin axis almost lies in the plane of the planet’s orbit. This results in the planet going through radical seasonal changes along its 84-year-long trek around the Sun. The consequence of the planet’s tilt means part of one hemisphere is completely without sunlight, for stretches of time lasting up to 42 years. OPAL has followed the northern pole now tipping toward the Sun.

With OPAL, Hubble first imaged Uranus after the spring equinox, when the Sun was last shining directly over the planet’s equator. Hubble resolved multiple storms with methane ice-crystal clouds appearing at mid-northern latitudes as summer approaches the north pole. Uranus’ north pole now has a thickened photochemical haze with several little storms near the edge of the boundary. Hubble has been tracking the size of the north polar cap and it continues to get brighter year after year. As the northern summer solstice approaches in 2028, the cap may grow brighter still, and will be aimed directly toward Earth, allowing good views of the rings and north pole. The ring system will then appear face-on.

Neptune

When Voyager 2 flew by Neptune 1989, astronomers were mystified by a great dark spot the size of the Atlantic Ocean looming in the atmosphere. Was it long-lived like Jupiter’s Great Red Spot? The question remained unanswered until Hubble was able to show in 1994 that such dark storms were transitory, cropping up and then disappearing over a duration of two to six years each. During the OPAL program, Hubble saw the end of one dark spot and the full life cycle of a second one – both of them migrating toward the equator before dissipating. The OPAL program ensures that astronomers won’t miss another one.

Hubble observations uncovered a link between Neptune’s shifting cloud abundance and the 11-year solar cycle. The connection between Neptune and solar activity is surprising to planetary scientists because Neptune is our solar system’s farthest major planet. It receives sunlight with about 0.1% of the intensity Earth receives. Yet Neptune’s global cloudy weather seems to be influenced by solar activity. Do the planet’s four seasons (each lasting approximately 40 years) also play a role? We may find out, if the OPAL program continues running on Hubble until the year 2179!

A montage of Hubble Space Telescope images of our solar system’s four giant outer planets: Jupiter, Saturn, Uranus, and Neptune, taken under the OPAL (Outer Planet Atmospheres Legacy) program over a duration of 10 years, from 2014 to 2024. — This is a montage of NASA/ESA Hubble Space Telescope views of our solar system’s four giant outer planets: Jupiter, Saturn, Uranus, and Neptune, each shown in enhanced color. The images were taken over nearly 10 years, from 2014 to 2024. This long baseline allows astronomers to track seasonal changes in each planet’s turbulent atmosphere, with the sharpness of the NASA planetary flyby probes of the 1980s. These images were taken under a program called OPAL (Outer Planet Atmospheres Legacy).
From upper-left toward center, the hazy white polar cap on the three teal-colored Uranus images appears more face-on as the planet approaches northern summer.
From center-right to far-center right, three images of the blue planet Neptune show the coming and going of clouds as the Sun’s radiation level changes. Several of Neptune’s mysterious dark spots have come and gone sequentially over OPAL’s decade of observations.
Seven views of yellow-brown Saturn stretch across the center of the mosaic in a triangle—one for each year of OPAL observations—showing the tilt of the angle of the ring plane relative to the view from Earth. Approximately every 15 years the relatively paper-thin rings (about one mile thick) can be seen edge-on. In 2018 they were near their maximum tilt toward Earth. Colorful changes in Saturn’s bands of clouds can be followed as the weather changes.
At bottom center, three images of Jupiter spanning nearly a decade, form a triangle. There are notable changes in Jupiter’s banded cloud structure of zones and belts. OPAL measured shrinking of the legendary Great Red Spot, while its rotation period speeds up.
Credit: NASA, ESA, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)

Press release from ESA Hubble.

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