Hubble sees white dwarf eating piece of Pluto-like object: a new study reports the accretion of an icy extrasolar planetesimal on to WD 1647+375
In our nearby stellar neighbourhood, a burned-out star is snacking on a fragment of a Pluto-like object. With its unique ultraviolet capability, only the NASA/ESA Hubble Space Telescope could identify that this meal is taking place.
The stellar remnant is a white dwarf about half the mass of our Sun, but that is densely packed into a body about the size of Earth. Scientists think the dwarf’s immense gravity pulled in and tore apart an icy Pluto analogue from the system’s own version of the Kuiper Belt, an icy ring of debris that encircles our Solar System. The findings were reported on 18 September 2025 in the Monthly Notices of the Royal Astronomical Society.
An international team of astronomers were able to determine this carnage by analysing the chemical composition of the doomed object as its pieces fell onto the white dwarf. In particular, they detected “volatiles” (substances with low boiling points) including carbon, sulphur, nitrogen, and a high oxygen content that suggests the strong presence of water.
“We were surprised,” said Snehalata Sahu of the University of Warwick in the United Kingdom. Sahu led the data analysis of a Hubble survey of white dwarfs. “We did not expect to find water or other icy content. This is because the comets and Kuiper Belt-like objects are thrown out of their planetary systems early, as their stars evolve into white dwarfs. But here, we are detecting this very volatile-rich material. This is surprising for astronomers studying white dwarfs as well as exoplanets, planets outside our Solar System.”
Only with Hubble
Using Hubble’s Cosmic Origins Spectrograph, the team found that the fragments were composed of nearly two thirds water ice. The fact that they detected so much ice meant that the pieces were part of a very massive object that formed far out in the star system’s icy Kuiper Belt analogue. Using Hubble data, scientists calculated that the object was bigger than typical comets and may be a fragment of an exo-Pluto.
They also detected a large fraction of nitrogen – the highest ever detected in white dwarf debris systems.
“We know that Pluto’s surface is covered with nitrogen ices,” said Sahu. “We think that the white dwarf accreted fragments of the crust and mantle of a dwarf planet.”
Accretion of these volatile-rich objects by white dwarfs is very difficult to detect in visible light. These volatile elements can only be detected with Hubble’s unique ultraviolet light sensitivity. In optical light, the white dwarf would appear ordinary.
About 260 light-years away, the white dwarf is a relatively close cosmic neighbor. In the past, when it was a Sun-like star, it would have been expected to host planets and an analogue to our Kuiper Belt.
Like seeing our Sun in the future
Billions of years from now, when our Sun burns out and collapses to a white dwarf, Kuiper Belt objects will be pulled in by the stellar remnant’s immense gravity.
“These planetesimals will then be disrupted and accreted,” said Sahu. “If an alien observer looks into our Solar System in the far future, they might see the same kind of remains we see today around this white dwarf.”
The team hopes to use the NASA/ESA/CSA James Webb Space Telescope to detect molecular features of volatiles such as water vapour and carbonates by observing this white dwarf in infrared light. By further studying white dwarfs, scientists can better understand the frequency and composition of these volatile-rich accretion events.
Sahu is also following the recent discovery of the interstellar comet 3I/ATLAS. She is eager to learn its chemical composition, especially its fraction of water.
“These types of studies will help us learn more about planet formation. They can also help us understand how water is delivered to rocky planets,” said Sahu.
Boris Gänsicke, of the University of Warwick and a visitor at Spain’s Instituto de Astrofisica de Canarias, was the principal investigator of the Hubble program that led to this discovery.
“We observed over 500 white dwarfs with Hubble. We’ve already learned so much about the building blocks and fragments of planets, but I’ve been absolutely thrilled that we now identified a system that resembles the objects in the frigid outer edges of our solar system,” said Gänsicke. “Measuring the composition of an exo-Pluto is an important contribution toward our understanding of the formation and evolution of these bodies.”
Thanks to the Hubble Space Telescope, a new study reports the accretion of an icy extrasolar planetesimal on to white dwarf WD 1647+375. This artist’s concept shows a white dwarf surrounded by a large debris disc. Debris from pieces of a captured, Pluto-like object is falling onto the white dwarf. Credit: T. Pyle (Caltech, NASA’s Jet Propulsion Laboratory)
Bibliographic information:
Snehalata Sahu, Boris T Gänsicke, Jamie T Williams, Detlev G Koester, Jay Farihi, Steven J Desch, Nicola Pietro Gentile Fusillo, Dimitri Veras, Sean N Raymond, Maria Teresa Belmonte, Discovery of an icy and nitrogen-rich extrasolar planetesimal, Monthly Notices of the Royal Astronomical Society, Volume 543, Issue 1, October 2025, Pages 223–232, https://doi.org/10.1093/mnras/staf1424
WD 0525+526: Hubble uncovers rare white dwarf merger remnant
An international team of astronomers using the NASA/ESA Hubble Space Telescope have discovered a stellar rarity: an ultra-massive white dwarf that formed when a white dwarf merged with another star, rather than through the evolution of a single star. This discovery, which was made possible by Hubble’s sensitive ultraviolet observations, suggests that these rare white dwarfs may be more common than previously suspected.
A white dwarf is the end state for a star that is not massive enough to explode as a core-collapse supernova. The transition to a white dwarf begins when a star exhausts the supply of hydrogen in its core. The changes in and around the star’s core cause the star to expel its outer layers in a massive stellar sigh, revealing the star’s dense, Earth-sized core, which evolves into a white dwarf. The cores of white dwarfs are mostly composed of either carbon and oxygen or oxygen and neon, depending on the mass of the progenitor star. The Sun will become a white dwarf in about 5 billion years.
White dwarfs can theoretically have masses up to about 1.4 times the mass of the Sun, but white dwarfs that are more massive than the Sun are rare. These objects, which astronomers call ultra-massive white dwarfs, can form either through the evolution of a single massive star or through the merger of a white dwarf with another star.
Recently, astronomers used Hubble’s Cosmic Origins Spectrograph to investigate one such ultra-massive white dwarf, WD 0525+526. WD 0525+526 is just 128 light-years away and is 20% more massive than the Sun.
In visible light, the spectrum of WD 0525+526’s atmosphere resembled that of a typical white dwarf. However, Hubble’s ultraviolet spectrum revealed something unusual: evidence of carbon in the white dwarf’s atmosphere.
White dwarfs that form through the evolution of a single star have atmospheres composed of hydrogen and helium. These thick atmospheres blanket the carbon–oxygen or oxygen–neon surface of the white dwarf, usually preventing these elements from appearing in its spectrum.
When carbon appears in the spectrum of a white dwarf, it can signal a more violent origin than the typical single-star scenario: the collision of two white dwarfs, or of a white dwarf and a subgiant star. Such a collision can burn away the hydrogen and helium atmospheres of the colliding stars, leaving behind a scant layer of hydrogen and helium around the merger remnant that allows carbon from the white dwarf’s core to float upward, where it can be detected.
“It’s a discovery that underlines that things may be different from what they appear to us at first glance,” said the principal investigator of the Hubble programme, Boris Gaensicke, of the University of Warwick in the United Kingdom. “Until now, this appeared as a normal white dwarf, but Hubble’s ultraviolet eyes revealed that it had a very different history from what we would have guessed. It’s like asking a person you think you know well a different kind of question.”
This discovery marks the first time that a white dwarf born from colliding stars has been identified by its ultraviolet spectrum. Prior to this study, six white dwarf merger products were discovered via carbon lines in their visible-light spectra. All seven of these are part of a larger group that were found to be bluer than expected for their masses and ages from a study with ESA’s Gaia mission in 2019, with the evidence of mergers providing new insights into their formation history.
WD 0525+526 is remarkable even within the small group of white dwarfs known to be the product of merging stars. With a temperature of almost 21 000 kelvins and a mass of 1.2 solar masses, WD 0525+526 is hotter and more massive than the other white dwarfs in this group.
WD 0525+526’s extreme temperature posed something of a mystery for the team. For cooler white dwarfs, such as the six previously discovered merger products, a process called convection can mix carbon into the thin hydrogen–helium atmosphere. WD 0525+526 is too hot for convection to take place, however. Instead, the team determined that a more subtle process called semi-convection brings a small amount of carbon up into WD 0525+526’s atmosphere. WD 0525+526 has the smallest amount of atmospheric carbon of any white dwarf known to result from a merger, about 100 000 times less than other merger remnants.
The high temperature and low carbon abundance mean that identifying this white dwarf as the product of a merger would have been impossible without Hubble’s sensitivity to ultraviolet light; spectral lines from elements heavier than helium, like carbon, become fainter at visible wavelengths for hotter white dwarfs, but these spectral signals remain bright in the ultraviolet, where Hubble is uniquely positioned to spot them.
“Hubble’s Cosmic Origins Spectrograph is the only instrument that can obtain the superb quality ultraviolet spectroscopy that was required to detect the carbon in the atmosphere of this white dwarf,” said study lead Snehalata Sahu from the University of Warwick.
Because WD 0525+526’s unusual origin was revealed only once astronomers glimpsed its ultraviolet spectrum, it’s likely that other seemingly ‘normal’ white dwarfs are actually the result of cosmic collisions — a possibility that the team is excited to explore in the future.
“We would like to extend our research on this topic by exploring how common carbon white dwarfs are, and how many stellar mergers are hiding among the normal white dwarf family,” said study co-lead Antoine Bedrad from the University of Warwick. “That will be an important contribution to our understanding of white dwarf binaries, and the pathways to supernova explosions.”
This image is an illustration of a merging white dwarf remnant. An international team of astronomers using the NASA/ESA Hubble Space Telescope have discovered a stellar rarity: an ultra-massive white dwarf that formed when a white dwarf merged with another star, rather than through the evolution of a single star. This discovery, which was made possible by Hubble’s sensitive ultraviolet observations, suggests that these rare white dwarfs may be more common than previously suspected. Credit: NASA, ESA, R. Crawford (STScI)
Bibliographic information:
Sahu, S., Bédard, A., Gänsicke, B.T. et al. A hot white dwarf merger remnant revealed by an ultraviolet detection of carbon, Nat Astron (2025), DOI: https://doi.org/10.1038/s41550-025-02590-y
Hubble makes size estimate of interstellar comet 3I/ATLAS
A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS, using the crisp vision of the NASA/ESA Hubble Space Telescope.
This image of interstellar comet 3I/ATLAS was captured by the Hubble Space Telescope’s Wide Field Camera on 21 July 2025. The scale bar is labeled in arcseconds, which is a measure of angular distance on the sky. One arcsecond is equal to an angular measurement of 1/3600 of one degree. There are 60 arcminutes in a degree and 60 arcseconds in an arcminute (the full Moon has an angular diameter of about 30 arcminutes). The actual size of an object that covers one arcsecond on the sky depends on its distance from the telescope. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). This image shows visible wavelengths of light. Credit: NASA, ESA, D. Jewitt (UCLA); Image Processing: J. DePasquale (STScI)
Hubble’s observations are allowing astronomers to more accurately estimate the size of the comet’s solid icy nucleus. The upper limit on the diameter of the nucleus is 5.6 kilometers, though it could be as small as 320 metres across, researchers report. Though the Hubble images put tighter constraints on the nucleus size compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Observations from other observatories, including the NASA/ESA/CSA James Webb Space Telescope, will help refine our knowledge about the comet, including its chemical makeup.
Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data yields a dust-loss rate consistent with comets that are first detected around 480 million kilometres from the Sun. This behaviour is much like the signature of previously seen Sun-bound comets originating within our Solar System.
The big difference is that this interstellar visitor originated in some other Solar System elsewhere in our Milky Way galaxy.
3I/ATLAS is traveling through our Solar System at roughly 210,000 kilometres per hour, the highest velocity ever recorded for a Solar System visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.
This comet was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 1 July 2025 at a distance of 675 million kilometres from the Sun. 3I/ATLAS should remain visible to ground-based telescopes through September, after which it will pass too close to the Sun to observe and is expected to reappear on the other side of the Sun by early December.
The paper will be published in The Astrophysical Journal Letters. It is already available here.
This is a Hubble Space telescope image of the interstellar comet 3I/ATLAS. Hubble photographed the comet on 21 July 21 2025, when the comet was 365 million kilometres from Earth. Hubble shows that the comet has a teardrop-shaped cocoon of dust coming off its solid, icy nucleus. Because Hubble was tracking the comet moving along a hyperbolic trajectory, the stationary background stars are streaked in the exposure. Credit: NASA, ESA, D. Jewitt (UCLA); Image Processing: J. DePasquale (STScI)
Webb scratches beyond the surface of the Cat’s Paw Nebula (NGC 6334) for third anniversary
To mark its third year of highly productive science, astronomers used the NASA/ESA/CSA James Webb Space Telescope to scratch beyond the surface of the Cat’s Paw Nebula (NGC 6334), a massive, local star-forming region.
Webb’s NIRCam instrument was used to look at this particular area of the Cat’s Paw Nebula, which just scratches the surface of the telescope’s three years of groundbreaking science.
To celebrate the NASA/ESA/CSA James Webb Space Telescope’s third year of highly productive science, astronomers used the telescope to scratch beyond the surface of the Cat’s Paw Nebula (NGC 6334), a massive, local star-forming region. This area is of great interest to scientists, having been subject to previous study by NASA’s Hubble and retired Spitzer space telescopes, as they seek to understand the multiple steps required for a turbulent molecular cloud to transition to stars. With its near-infrared capabilities and sharp resolution, the telescope “clawed” back a portion of a singular “toe bean,” revealing a subset of mini toe bean-reminiscent structures composed of gas, dust, and young stars. Webb’s view reveals a chaotic scene still in development: Massive young stars are carving away at nearby gas and dust, while their bright starlight is producing a bright nebulous glow represented in blue. This is only a chapter in the region’s larger story. The disruptive young stars, with their relatively short lifespans and luminosity, will eventually quench the local star formation process. The Cat’s Paw Nebula is located approximately 4,000 light-years away in the constellation Scorpius. Credit: NASA, ESA, CSA, STScI
A star formation flex
The progression from a large molecular cloud to massive stars entails multiple steps, some of which are still not well understood by astronomers. Located approximately 4,000 light-years away in the constellation Scorpius, the Cat’s Paw Nebula offers scientists the opportunity to study the turbulent cloud-to-star process in great detail. Webb’s observation of the nebula in near-infrared light builds upon previous studies by the NASA/ESA Hubble and retired NASA Spitzer Space Telescope in visible- and infrared-light, respectively.
With its sharp resolution, Webb shows never-before-seen structural details and features: Massive young stars are carving away at nearby gas and dust, while their bright starlight is producing a bright nebulous glow represented in blue. It’s a temporary scene where the disruptive young stars, with their relatively short lifespans and luminosity, have a brief but important role in the region’s larger story. As a consequence of these massive stars’ lively behavior, the local star formation process will eventually come to a stop.
The opera house’s intricate structure
Start with the region at top centre, which is nicknamed the “Opera House” for its circular, tiered-like structure. The primary drivers for the area’s cloudy blue glow are most likely toward its bottom: either the light from the bright yellowish stars or from a nearby source still hidden behind the dense, dark brown dust.
Just below the orange-brown tiers of dust is a bright yellow star with diffraction spikes. While this massive star has carved away at its immediate surroundings, it has been unable to push the gas and dust away to greater distances, creating a compact shell of surrounding material.
Look closely to notice small patches, like the tuning fork-shaped area to the Opera House’s immediate left, that contain fewer stars. These seemingly vacant zones indicate the presence of dense foreground filaments of dust that are home to still-forming stars and block the light of stars in the background.
A spotlight on stars
Toward the image’s centre are small, fiery red clumps scattered amongst the brown dust. These glowing red sources mark regions where massive star formation is underway, albeit in an obscured manner.
Some massive blue-white stars, like the one in the lower left region, seem to be more sharply resolved than others. This is because any intervening material between the star and the telescope has been dissipated by stellar radiation.
Near the bottom of this region are small, dense filaments of dust. These tiny clumps of dust have managed to remain despite the intense radiation, suggesting that they are dense enough to form protostars. A small section of yellow at the right notes the location of a still-enshrouded massive star that has managed to shine through intervening material.
Across this entire scene are many small yellow stars with diffraction spikes. Bright blue-white stars are in the foreground of this Webb image, but some may be a part of the more expansive Cat’s Paw Nebula area.
One eye-catching aspect of this Webb image is the bright, red-orange oval at top right. Its low count of background stars implies it is a dense area just beginning its star-formation process. A couple of visible and still-veiled stars are scattered throughout this region, which are contributing to the illumination of the material in the middle. Some still-enveloped stars leave hints of their presence, like a bow shock at the bottom left, which indicates an energetic ejection of gas and dust from a bright source.
Another incredible year of science and images
Webb continued to return on its ambitious science goals over its third year of operations. Unexpected, bright hydrogen emission was found in the galaxy GZ-z13-1, a mere 330 million years after the Big Bang. Showcasing its coronagraph, Webb took direct images of exoplanets in the HR 8799 system which revealed how they likely formed. Then, astronomers discovered a potential new exoplanet in the debris disc around star TWA 7, the first such discovery made with Webb’s coronagraph — but surely not the last. Closer to home, astronomers were able to watch aurorae unfold over a period of just hours on Jupiter.
A remarkable view of a rare Einstein ring, a rich collection of galaxies that acts as a lens on the distant past, a protoplanetary disc sporting powerful stellar winds, and the Sombrero Galaxy seen in an entirely new light were just some of the images released over the past year through which Webb showed us a new view of the cosmos.
In a particular highlight from Webb, the first discovery of young brown dwarf stars outside our galaxy produced a truly breathtaking image of star cluster NGC 602, a vista of its many colours of ionised gas.
To celebrate the NASA/ESA/CSA James Webb Space Telescope’s third year of highly productive science, astronomers used the telescope to scratch beyond the surface of the Cat’s Paw Nebula (NGC 6334), a massive, local star-forming region. This area is of great interest to scientists, having been subject to previous study by NASA’s Hubble and retired Spitzer space telescopes, as they seek to understand the multiple steps required for a turbulent molecular cloud to transition to stars. With its near-infrared capabilities and sharp resolution, the telescope “clawed” back a portion of a singular “toe bean,” revealing a subset of mini toe bean-reminiscent structures composed of gas, dust, and young stars. Webb’s view reveals a chaotic scene still in development: Massive young stars are carving away at nearby gas and dust, while their bright starlight is producing a bright nebulous glow represented in blue. This is only a chapter in the region’s larger story. The disruptive young stars, with their relatively short lifespans and luminosity, will eventually quench the local star formation process. The Cat’s Paw Nebula is located approximately 4,000 light-years away in the constellation Scorpius. Credit: NASA, ESA, CSA, STScI
Hubble and a new study published in Nature Astronomy cast doubt on the certainty of a collision between the Milky Way and the Andromeda galaxy
Over a decade’s worth of NASA/ESA Hubble Space Telescope data was used to re-examine the long-held prediction that the Milky Way galaxy will collide with the Andromeda galaxy in about 4.5 billion years. The astronomers found that, based on the latest observational data from Hubble as well as the Gaia space telescope, there is only a 50-50 chance of the two galaxies colliding within the next 10 billion years. The study also found that the presence of the Large Magellanic Cloud can affect the trajectory of the Milky Way and make the collision less likely. The researchers emphasize that predicting the long-term future of galaxy interactions is highly uncertain, but the new findings challenge the previous consensus and suggest the fate of the Milky Way remains an open question.
Hubble and a new study published in Nature Astronomy cast doubt on the certainty of a collision between the Milky Way and the Andromeda galaxy. This selection of images of external galaxies illustrates three encounter scenarios between our Milky Way and the neighboring Andromeda galaxy. In the top left panel, a wide-field DSS image showing galaxies M81 and M82 serves as an example of the Milky Way and Andromeda passing each other at large distances. The top right panel shows NGC 6786, a pair of interacting galaxies displaying the telltale signs of tidal disturbances after a close encounter. The bottom panel shows NGC 520, a cosmic train wreck as two galaxies are actively merging together. Credit: NASA, ESA, STScI, Till Sawala (University of Helsinki), DSS, J. DePasquale (STScI)
As far back as 1912, astronomers realized that the Andromeda galaxy — then thought to be only a nebula — was headed our way. A century later, astronomers using the NASA/ESA Hubble Space Telescope were able to measure the sideways motion of Andromeda and found it was so negligible that an eventual head-on collision with the Milky Way seemed almost certain.
A smashup between our own galaxy and Andromeda would trigger a firestorm of star birth, supernovae, and maybe toss our Sun into a different orbit. Simulations had suggested it was inevitable.
However, a new study using data from Hubble and ESA’s Gaia suggests this may not necessarily be the case. Researchers combining observations from the two space observatories re-examined the long-held prediction of a Milky Way – Andromeda collision, and found it is far less inevitable than astronomers had previously suspected.
“We have the most comprehensive study of this problem today that actually folds in all the observational uncertainties,” said Till Sawala, astronomer at the University of Helsinki in Finland and lead author of the study, which appears today in the journal Nature Astronomy.
His team includes researchers at Durham University, United Kingdom; the University of Toulouse, France; and the University of Western Australia. They found that there is approximately a 50-50 chance of the two galaxies colliding within the next 10 billion years. They based this conclusion on computer simulations using the latest observational data.
Sawala emphasized that predicting the long-term future of galaxy interactions is highly uncertain, but the new findings challenge the previous consensus and suggest the fate of the Milky Way remains an open question.
“Even using the latest and most precise observational data available, the future of the Local Group of several dozen galaxies is uncertain. Intriguingly, we find an almost equal probability for the widely publicized merger scenario, or, conversely, an alternative one where the Milky Way and Andromeda survive unscathed,” said Sawala.
The collision of the two galaxies had seemed much more likely in 2012, when astronomers Roeland van der Marel and Tony Sohn of the Space Telescope Science Institute in Baltimore, Maryland published a detailed analysis of Hubble observations over a five-to-seven-year period, indicating a direct impact in no more than 5 billion years.
“It’s somewhat ironic that, despite the addition of more precise Hubble data taken in recent years, we are now less certain about the outcome of a potential collision. That’s because of the more complex analysis and because we consider a more complete system. But the only way to get to a new prediction about the eventual fate of the Milky Way will be with even better data,” said Sawala.
Astronomers considered 22 different variables that could affect the potential collision between our galaxy and our neighbor, and ran 100,000 simulations called Monte Carlo simulations stretching to 10 billion years into the future.
“Because there are so many variables that each have their errors, that accumulates to rather large uncertainty about the outcome, leading to the conclusion that the chance of a direct collision is only 50% within the next 10 billion years,” said Sawala.
“The Milky Way and Andromeda alone would remain in the same plane as they orbit each other, but this doesn’t mean they need to crash. They could still go past each other,” said Sawala.
Researchers also considered the effects of the orbits of Andromeda’s large satellite galaxy, M33, and a satellite galaxy of the Milky Way called the Large Magellanic Cloud (LMC).
“The extra mass of Andromeda’s satellite galaxy M33 pulls the Milky Way a little bit more towards it. However, we also show that the LMC pulls the Milky Way off the orbital plane and away from Andromeda. It doesn’t mean that the LMC will save us from that merger, but it makes it a bit less likely,” said Sawala.
In about half of the simulations, the two main galaxies fly past each other separated by around half a million light-years or less (five times the Milky Way’s diameter). They move outward but then come back and eventually merge in the far future. The gradual decay of the orbit is caused by a process called dynamical friction between the vast dark-matter halos that surround each galaxy at the beginning.
In most of the other cases, the galaxies don’t even come close enough for dynamical friction to work effectively. In this case, the two galaxies can continue their orbital waltz for a very long time.
The new result also still leaves a small chance of around 2% for a head-on collision between the galaxies in only 4 to 5 billion years. Considering that the warming Sun makes Earth uninhabitable in roughly 1 billion years, and the Sun itself will likely burn out in 5 billion years, a collision with Andromeda is the least of our cosmic worries.
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.
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
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
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.
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.
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
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.
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.
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).
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
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)
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
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.
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
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 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 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.
