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Webb hints at possible atmosphere surrounding 55 Cancri e, a rocky exoplanet

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55 Cancri e Illustration of a rocky exoplanet and its star. The star is in the background at the lower left and appears somewhat smaller in the sky than the planet. The planet has hints of a rocky, partly molten surface beneath the haze of a thin atmosphere.

Webb hints at possible atmosphere surrounding 55 Cancri e, a rocky exoplanet

 

Researchers using the NASA/ESA/CSA James Webb Space Telescope may have detected atmospheric gases surrounding 55 Cancri e, a hot rocky exoplanet 41 light-years from Earth. This is the best evidence to date for the existence of a rocky planet atmosphere outside our Solar System.

Renyu Hu from NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, USA, is the lead author of a paper published today in Nature.

“Webb is pushing the frontiers of exoplanet characterisation to rocky planets,” Hu said. “It is truly enabling a new type of science.”

Super-hot super-Earth 55 Cancri e

55 Cancri e is one of five known planets orbiting a Sun-like star in the constellation Cancer. With a diameter nearly twice that of Earth and a density slightly greater, the planet is classified as a super-Earth: larger than Earth, smaller than Neptune, and likely similar in composition to the rocky planets in our Solar System.

To describe 55 Cancri e as rocky, however, could give the wrong impression. The planet orbits so close to its star (about 2.25 million kilometres, or one twenty-fifth of the distance between Mercury and the Sun) that its surface is likely to be molten – a bubbling ocean of magma. In such a tight orbit, the planet is also likely to be tidally locked, with a dayside that faces the star at all times and a nightside in perpetual darkness.

In spite of numerous observations since it was discovered to transit in 2011, the question of whether or not 55 Cancri e has an atmosphere – or even could have one, given its high temperature and the continuous onslaught of stellar radiation and wind from its star – has gone unanswered.

“I’ve worked on this planet for more than a decade,” said Diana Dragomir, an exoplanet researcher at the University of New Mexico in the USA and a co-author of the study. “It’s been really frustrating that none of the observations we’ve been getting have robustly solved these mysteries. I am thrilled that we are finally getting some answers!”

Unlike gas-giant atmospheres, which are relatively easy to spot (the first was detected by the NASA/ESA Hubble Space Telescope more than two decades ago), thinner and denser atmospheres surrounding rocky planets have remained elusive.

Previous studies of 55 Cancri e using data from NASA’s now-retired Spitzer Space Telescope suggested the presence of a substantial atmosphere rich in volatiles (molecules that occur in gas form on Earth) like oxygen, nitrogen, and carbon dioxide. But researchers could not rule out another possibility: that the planet is bare, save for a tenuous shroud of vaporised rock, rich in elements like silicon, iron, aluminium, and calcium.

“The planet is so hot that some of the molten rock should evaporate,” explained Hu.

Illustration of a rocky exoplanet and its star. The star is in the background at the lower left and appears somewhat smaller in the sky than the planet. The planet has hints of a rocky, partly molten surface beneath the haze of a thin atmosphere.
This artist’s concept shows what the exoplanet 55 Cancri e could look like.
Also called Janssen, 55 Cancri e is a so-called super-Earth, a rocky planet significantly larger than Earth but smaller than Neptune, which orbits its star at a distance of only 2.25 million kilometres (0.015 astronomical units), completing one full orbit in less than 18 hours. In comparison, Mercury is 25 times farther from the Sun than 55 Cancri e is from its star. The system, which also includes four large gas-giant planets, is located about 41 light-years from Earth, in the constellation Cancer.
Observations from Webb’s NIRCam and MIRI suggest that the planet may be surrounded by an atmosphere rich in carbon dioxide (CO2) or carbon monoxide (CO). Because it is so close to its star, the planet is extremely hot and is thought to be covered in molten rock. Researchers think that the gases that make up the atmosphere could have bubbled out of the magma.
The star, 55 Cancri, is a K-type star nearly the same size and mass as the Sun, but slightly cooler and dimmer. It is just bright enough to see with the naked eye in a very dark sky. The star and planet are so close to each other that the star would appear 70 times wider in the planet’s sky than the Sun appears in our sky. In addition, because the planet is likely to be tidally locked, from any given point the star would appear fixed in the sky.
This artist’s concept is based on new data gathered by NIRCam and MIRI as well as previous observations from other ground- and space-based telescopes, including NASA’s Hubble and the now-retired Spitzer space telescopes. Webb has not captured any images of the planet.
Credit: NASA, ESA, CSA, R. Crawford (STScI)

Measuring subtle variations in infrared colours

To distinguish between the two possibilities, the team used Webb’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) to measure 4- to 12-micron infrared light coming from the planet.

Although Webb cannot capture a direct image of 55 Cancri e, it can measure subtle changes in the light from the whole system as the planet orbits the star.

By subtracting the brightness during the secondary eclipse, when the planet is behind the star (starlight only), from the brightness when the planet is right beside the star (light from the star and planet combined), the team was able to calculate the amount of various wavelengths of infrared light coming from the dayside of the planet.

This method, known as secondary eclipse spectroscopy, is similar to that used by other research teams to search for atmospheres on other rocky exoplanets, like TRAPPIST-1 b.

Diagram of a secondary eclipse and a graph of change in brightness over time. Below the diagram is a graph showing the change in brightness of mid-infrared light emitted by the star-planet system over the course of about four and a half hours. The infographic shows that the brightness of the system decreases as the planet moves behind the star.
This lightcurve shows the change in brightness of the 55 Cancri system as the rocky planet 55 Cancri e, the closest of the five known planets in the system, moves behind the star. This phenomenon is known as a secondary eclipse.
When the planet is beside the star, the mid-infrared light emitted by both the star and the dayside of the planet reaches the telescope, and the system appears brighter. When the planet is behind the star, the light emitted by the planet is blocked and only the starlight reaches the telescope, causing the apparent brightness to decrease.
Astronomers can subtract the brightness of the star from the combined brightness of the star and planet to calculate how much infrared light is coming from the dayside of the planet. This is then used to calculate the dayside temperature and infer whether or not the planet has an atmosphere.
The graph shows data collected using the low-resolution spectroscopy mode on Webb’s Mid-Infrared Instrument (MIRI) in March 2023. Each of the purple data points shows the brightness of light ranging in wavelength from 7.5 to 11.8 microns, averaged over intervals of about five minutes. The grey line is the best fit, or model lightcurve that matches the data most closely. The decrease in brightness during the secondary eclipse is just 110 parts per million, or about 0.011 percent.
The temperature of the planet calculated from this observation is about 1800 kelvins (around 1500 degrees Celsius), which is significantly lower than would be expected if the planet has no atmosphere or only a thin rock-vapour atmosphere. This relatively low temperature indicates that heat is being distributed from the dayside to the nightside of the planet, possibly by a volatile-rich atmosphere.
Credit: NASA, ESA, CSA, J. Olmsted (STScI), A. Bello-Arufe (JPL)

 55 Cancri e is cooler than expected

The first indication that 55 Cancri e could have a substantial atmosphere came from temperature measurements based on its thermal emission, the heat energy given off in the form of infrared light. If the planet is covered in dark molten rock with a thin veil of vaporised rock, or has no atmosphere at all, the dayside should be around 2200 degrees Celsius.

“Instead, the MIRI data showed a relatively low temperature of about 1540 degrees Celsius,” said Hu. “This is a very strong indication that energy is being distributed from the dayside to the nightside, most likely by a volatile-rich atmosphere.”

 While currents of lava can carry some heat around to the nightside, they cannot move it efficiently enough to explain the cooling effect.

When the team looked at the NIRCam data, they saw patterns consistent with a volatile-rich atmosphere.

“We see evidence of a dip in the spectrum between 4 and 5 microns — less of this light is reaching the telescope,” explained co-author Aaron Bello-Arufe, also from JPL. “This suggests the presence of an atmosphere containing carbon monoxide or carbon dioxide, both of which absorb these wavelengths of light.”

A planet with no atmosphere or only vaporised rock in an atmosphere would not have this specific spectral feature.

“This is exciting news,” said co-author Yamila Miguel from Leiden Observatory and the Netherlands Institute for Space Research (SRON), both in the Netherlands. “We’ve spent the last ten years modelling different scenarios, trying to imagine what this world might look like. Finally getting some confirmation of our work is priceless!”

Bubbling magma ocean

The team thinks that the gases blanketing 55 Cancri e would be bubbling out from the interior, rather than being present since the planet’s formation. 

“The primary atmosphere would be long gone because of the high temperature and intense radiation from the star,” said Bello-Arufe. “This would be a secondary atmosphere that is continuously replenished by the magma ocean. Magma is not only crystals and liquid rock, there’s a lot of dissolved gas in it, too.”

In all likelihood, any atmosphere surrounding the planet would be more complex and quite variable as a result of interactions with the magma ocean. In addition to carbon monoxide or carbon dioxide, there could be gases like nitrogen, water vapour, sulphur dioxide, some vaporised rock, and even short-lived clouds made of tiny droplets of lava condensed from the air.

While 55 Cancri e is far too hot to be habitable, researchers think it could provide a unique window for studying interactions between the atmospheres, surfaces and interiors of rocky planets, and perhaps provide insights into the early Earth, Venus and Mars, which are thought to have been covered in magma oceans in the past. 

“Ultimately, we want to understand what conditions make it possible for a rocky planet to sustain a gas-rich atmosphere, a key ingredient for a habitable planet,” said Hu.

This research was conducted as part of Webb’s General Observers (GO) Program 1952. Analysis of additional secondary eclipse observations of 55 Cancri e are currently in progress. In the future, the team hopes to capture a full phase curve with Webb in order to map temperature differences from one side of the planet to the other, to get a better sense of the planet’s weather, climate and more detailed atmospheric conditions.

Graph showing the brightness of light captured by Webb’s NIRCam and MIRI instruments plotted alongside two different model emission spectra, and an illustration of the planet and its star in the background.
A thermal emission spectrum captured by Webb’s NIRCam (Near-Infrared Camera) in November 2022, and MIRI (Mid-Infrared Instrument) in March 2023, shows the brightness (y-axis) of different wavelengths of infrared light (x-axis) emitted by the super-Earth exoplanet 55 Cancri e. The spectrum shows that the planet may be surrounded by an atmosphere rich in carbon dioxide or carbon monoxide and other volatiles, not just vaporised rock.
The graph compares data collected by NIRCam (orange dots) and MIRI (purple dots) to two different models. Model A, in red, shows what the emission spectrum of 55 Cancri e should look like if it has an atmosphere made of vaporised rock. Model B, in blue, shows what the emission spectrum should look like if the planet has a volatile-rich atmosphere outgassed from a magma ocean that has a volatile content similar to Earth’s mantle. Both MIRI and NIRCam data are consistent with the volatile-rich model.
The amount of mid-infrared light emitted by the planet (MIRI) shows that its dayside temperature is significantly lower than it would be if it did not have an atmosphere to distribute heat from the dayside to the nightside. The dip in the spectrum between 4 and 5 microns (NIRCam data) can be explained by absorption of those wavelengths by carbon monoxide or carbon dioxide molecules in the atmosphere.
The spectrum was made by measuring the brightness of 4- to 5-micron light with Webb’s NIRCam GRISM spectrometer, and 5- to 12-micron light with the MIRI low-resolution spectrometer, before, during and after the planet moved behind its star (the secondary eclipse ). The amount of each wavelength emitted by the planet (y-axis) was calculated by subtracting the brightness of the star alone (during the secondary eclipse) from the brightness of the star and planet combined (before and after the eclipse). Each observation lasted about eight hours.
Note that the NIRCam data have been shifted vertically to align with Model B. Although the differences in brightness between each wavelength in the NIRCam band were derived from the observation (the data suggest a valley between 4 and 5 microns), the absolute brightness (the vertical position of that valley) could not be measured precisely because of noise in the data.
Credit: NASA, ESA, CSA, J. Olmsted (STScI), R. Hu (JPL), A. Bello-Arufe (JPL), M. Zhang (University of Chicago), M. Zilinskas (SRON Netherlands Institute for Space Research)

Press release from ESA Webb.

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Webb captures iconic Horsehead Nebula in unprecedented detail

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At the bottom of the image a small portion of the Horsehead Nebula is seen close-in, as a curved wall of thick, smoky gas and dust. Above the nebula various distant stars and galaxies can be seen up to the top of the image. One star is very bright and large, with six long diffraction spikes that cross the image. The background fades from a dark red colour above the nebula to black.

Webb captures iconic Horsehead Nebula in unprecedented detail

 

The NASA/ESA/CSA James Webb Space Telescope has captured the sharpest infrared images to date of one of the most distinctive objects in our skies, the Horsehead Nebula. These observations show a part of the iconic nebula in a whole new light, capturing its complexity with unprecedented spatial resolution.

A collage of three images of the Horsehead Nebula. In the left image labelled “Euclid (Visible-Infrared)”, the Nebula is seen amongst its surroundings. A small box around it connects to the second image labelled “Hubble (Infrared)”, where the Nebula is zoomed in on. A portion of the Nebula’s head has another box, which leads with a callout to the third image, labelled “Webb (Infrared)”, of that area.
This image showcases three views of one of the most distinctive objects in our skies, the Horsehead Nebula. This object resides in part of the sky in the constellation Orion (The Hunter), in the western side of the Orion B molecular cloud. Rising from turbulent waves of dust and gas is the Horsehead Nebula, otherwise known as Barnard 33, which resides roughly 1300 light-years away.
The first image (left), released in November 2023, features the Horsehead Nebula as seen by ESA’s Euclid telescope. Euclid captured this image of the Horsehead in about one hour, which showcases the mission’s ability to very quickly image an unprecedented area of the sky in high detail.
The second image (middle) shows the NASA/ESA Hubble Space Telescope’s infrared view of the Horsehead Nebula, which was featured as the telescope’s 23rd anniversary image in 2013. This image captures plumes of gas in the infrared and reveals a beautiful, delicate structure that is normally obscured by dust.
The third image (right) features a new view of the Horsehead Nebula from the NASA/ESA/CSA James Webb Space Telescope’s NIRCam (Near-InfraRed Camera) instrument. It is the sharpest infrared image of the object to date, showing a part of the iconic nebula in a whole new light, and capturing its complexity with unprecedented spatial resolution.
Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi, NASA, ESA, and the Hubble Heritage Team (AURA/STScI), ESA/Webb, CSA, K. Misselt (University of Arizona) and A. Abergel (IAS/University Paris-Saclay, CNRS), M. Zamani (ESA/Webb)

Webb’s new images show part of the sky in the constellation Orion (The Hunter), in the western side of the Orion B molecular cloud. Rising from turbulent waves of dust and gas is the Horsehead Nebula, otherwise known as Barnard 33, which resides roughly 1300 light-years away.

The nebula formed from a collapsing interstellar cloud of material, and glows because it is illuminated by a nearby hot star. The gas clouds surrounding the Horsehead have already dissipated, but the jutting pillar is made of thick clumps of material that is harder to erode. Astronomers estimate that the Horsehead has about five million years left before it too disintegrates. Webb’s new view focuses on the illuminated edge of the top of the nebula’s distinctive dust and gas structure.

The Horsehead Nebula is a well-known photodissociation region, or PDR. In such a region ultraviolet light from young, massive stars creates a mostly neutral, warm area of gas and dust between the fully ionised gas surrounding the massive stars and the clouds in which they are born. This ultraviolet radiation strongly influences the gas chemistry of these regions and acts as the most important source of heat.

These regions occur where interstellar gas is dense enough to remain neutral, but not dense enough to prevent the penetration of far-ultraviolet light from massive stars. The light emitted from such PDRs provides a unique tool to study the physical and chemical processes that drive the evolution of interstellar matter in our galaxy, and throughout the Universe from the early era of vigorous star formation to the present day.

Owing to its proximity and its nearly edge-on geometry, the Horsehead Nebula is an ideal target for astronomers to study the physical structures of PDRs and the evolution of the chemical characteristics of the gas and dust within their respective environments, and the transition regions between them. It is considered one of the best objects in the sky to study how radiation interacts with interstellar matter.

At the bottom of the image a small portion of the Horsehead Nebula is seen close-in, as a curved wall of thick, smoky gas and dust. Above the nebula various distant stars and galaxies can be seen up to the top of the image. One star is very bright and large, with six long diffraction spikes that cross the image. The background fades from a dark red colour above the nebula to black.
The NASA/ESA/CSA James Webb Space Telescope has captured the sharpest infrared images to date of one of the most distinctive objects in our skies, the Horsehead Nebula. These observations show a part of the iconic nebula in a whole new light, capturing its complexity with unprecedented spatial resolution.
Webb’s new images show part of the sky in the constellation Orion (The Hunter), in the western side of the Orion B molecular cloud. Rising from turbulent waves of dust and gas is the Horsehead Nebula, otherwise known as Barnard 33, which resides roughly 1300 light-years away.
The nebula formed from a collapsing interstellar cloud of material, and glows because it is illuminated by a nearby hot star. The gas clouds surrounding the Horsehead have already dissipated, but the jutting pillar is made of thick clumps of material that is harder to erode. Astronomers estimate that the Horsehead has about five million years left before it too disintegrates. Webb’s new view focuses on the illuminated edge of the top of the nebula’s distinctive dust and gas structure.
The Horsehead Nebula is a well-known photon-dominated region, or PDR. In such a region ultraviolet light from young, massive stars creates a mostly neutral, warm area of gas and dust between the fully ionised gas surrounding the massive stars and the clouds in which they are born. This ultraviolet radiation strongly influences the gas chemistry of these regions and acts as the most important source of heat.
These regions occur where interstellar gas is dense enough to remain neutral, but not dense enough to prevent the penetration of far-ultraviolet light from massive stars. The light emitted from such PDRs provides a unique tool to study the physical and chemical processes that drive the evolution of interstellar matter in our galaxy, and throughout the Universe from the early era of vigorous star formation to the present day.
Owing to its proximity and its nearly edge-on geometry, the Horsehead Nebula is an ideal target for astronomers to study the physical structures of PDRs and the evolution of the chemical characteristics of the gas and dust within their respective environments, and the transition regions between them. It is considered one of the best objects in the sky to study how radiation interacts with interstellar matter.
This image was captured with Webb’s NIRCam (Near-InfraRed Camera) instrument.
Credit: ESA/Webb, NASA, CSA, K. Misselt (University of Arizona) and A. Abergel (IAS/University Paris-Saclay, CNRS)

Thanks to Webb’s MIRI and NIRCam instruments, an international team of astronomers have revealed for the first time the small-scale structures of the illuminated edge of the Horsehead. They have also detected a network of striated features extending perpendicular to the PDR front and containing dust particles and ionised gas entrained in the photo-evaporative flow of the nebula. The observations have also allowed astronomers to investigate the effects of dust attenuation and emission, and to better understand the multidimensional shape of the nebula.

The image is more than half-filled by a small section of the Horsehead Nebula, from the bottom up. The clouds are seen up close, showing thick, whitish streaks and dark voids, as well as textured, fuzzy-looking patterns of dust and gas. The nebula stops at a spiky edge that follows a slight curve. Above it a small number of distant stars and galaxies lie on a dark but multi-coloured background.
The NASA/ESA/CSA James Webb Space Telescope has captured the sharpest infrared images to date of one of the most distinctive objects in our skies, the Horsehead Nebula. These observations show a part of the iconic nebula in a whole new light, capturing its complexity with unprecedented spatial resolution.
Webb’s new images show part of the sky in the constellation Orion (The Hunter), in the western side of the Orion B molecular cloud. Rising from turbulent waves of dust and gas is the Horsehead Nebula, otherwise known as Barnard 33, which resides roughly 1300 light-years away.
The nebula formed from a collapsing interstellar cloud of material, and glows because it is illuminated by a nearby hot star. The gas clouds surrounding the Horsehead have already dissipated, but the jutting pillar is made of thick clumps of material that is harder to erode. Astronomers estimate that the Horsehead has about five million years left before it too disintegrates. Webb’s new view focuses on the illuminated edge of the top of the nebula’s distinctive dust and gas structure.
The Horsehead Nebula is a well-known photon-dominated region, or PDR. In such a region ultraviolet light from young, massive stars creates a mostly neutral, warm area of gas and dust between the fully ionised gas surrounding the massive stars and the clouds in which they are born. This ultraviolet radiation strongly influences the gas chemistry of these regions and acts as the most important source of heat.
These regions occur where interstellar gas is dense enough to remain neutral, but not dense enough to prevent the penetration of far-ultraviolet light from massive stars. The light emitted from such PDRs provides a unique tool to study the physical and chemical processes that drive the evolution of interstellar matter in our galaxy, and throughout the Universe from the early era of vigorous star formation to the present day.
Owing to its proximity and its nearly edge-on geometry, the Horsehead Nebula is an ideal target for astronomers to study the physical structures of PDRs and the evolution of the chemical characteristics of the gas and dust within their respective environments, and the transition regions between them. It is considered one of the best objects in the sky to study how radiation interacts with interstellar matter.
This image was captured with Webb’s MIRI (Mid-InfraRed Instrument).
Credit: ESA/Webb, NASA, CSA, K. Misselt (University of Arizona) and A. Abergel (IAS/University Paris-Saclay, CNRS)

Next, astronomers intend to study the spectroscopic data that have been obtained of the nebula to evidence the evolution of the physical and chemical properties of the material observed across the nebula.

These observations were taken in the Webb GTO programme #1192 (PI: K. Misselt) and the results have been accepted for publication in Astronomy & Astrophysics (Abergel et al. 2024).

 

Press release from ESA Webb.

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Hubble celebrates 34th anniversary with a look at the Little Dumbbell Nebula

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A Hubble image of the Little Dumbbell Nebula. The name comes from its shape, which is a two-lobed structure of colourful, mottled glowing gases that resemble a balloon that has been pinched around a middle waist. Like an inflating balloon, the lobes are expanding into space from a dying star seen as a white dot in the centre. Blistering ultraviolet radiation from the super-hot star is causing the gases to glow. The red colour is from nitrogen, and blue is from oxygen.

Hubble celebrates 34th anniversary with a look at the Little Dumbbell Nebula

In celebration of the 34th anniversary of the launch of the legendary NASA/ESA Hubble Space Telescope on 24 April, astronomers took a snapshot of the Little Dumbbell Nebula (also known as Messier 76, M76, or NGC 650/651) located 3400 light-years away in the northern circumpolar constellation Perseus. The photogenic nebula is a favourite target of amateur astronomers.

A Hubble image of the Little Dumbbell Nebula. The name comes from its shape, which is a two-lobed structure of colourful, mottled glowing gases that resemble a balloon that has been pinched around a middle waist. Like an inflating balloon, the lobes are expanding into space from a dying star seen as a white dot in the centre. Blistering ultraviolet radiation from the super-hot star is causing the gases to glow. The red colour is from nitrogen, and blue is from oxygen.
In celebration of the 34th anniversary of the launch of the legendary NASA/ESA Hubble Space Telescope, astronomers took a snapshot of the Little Dumbbell Nebula (also known as Messier 76, M76, or NGC 650/651) located 3400 light-years away in the northern circumpolar constellation Perseus. The photogenic nebula is a favourite target of amateur astronomers.
M76 is classified as a planetary nebula. This is a misnomer because it is unrelated to planets. But its round shape suggested it was a planet to astronomers who first viewed it through low-power telescopes. In reality, a planetary nebula is an expanding shell of glowing gases that were ejected from a dying red giant star. The star eventually collapses to an ultra-dense, hot white dwarf.
M76 is composed of a ring, seen edge-on as the central bar structure, and two lobes on either opening of the ring. Before the star burned out, it ejected the ring of gas and dust. The ring was probably sculpted by the effects of the star that once had a binary companion star. This sloughed-off material created a thick disc of dust and gas along the plane of the companion’s orbit. The hypothetical companion star isn’t seen in the Hubble image, and so it could have been later swallowed by the central star. The disc would be forensic evidence for that stellar cannibalism.
The primary star is collapsing to form a white dwarf. It is one of the hottest stellar remnants known at a scorching 120 000 degrees Celsius, 24 times our Sun’s surface temperature. The sizzling white dwarf can be seen as a pinpoint in the centre of the nebula. A star visible in projection beneath it is not part of the nebula.
Pinched off by the disc, two lobes of hot gas are escaping from the top and bottom of the ‘belt’ along the star’s rotation axis that is perpendicular to the disc. They are being propelled by the hurricane-like outflow of material from the dying star, tearing across space at two million miles per hour. That’s fast enough to travel from Earth to the Moon in a little over seven minutes! This torrential ‘stellar wind’ is ploughing into cooler, slower-moving gas that was ejected at an earlier stage in the star’s life, when it was a red giant. Ferocious ultraviolet radiation from the super-hot star is causing the gases to glow. The red colour is from nitrogen, and blue is from oxygen.
The entire nebula is a flash in the pan by cosmological timekeeping. It will vanish in about 15 000 years.
Credit: NASA, ESA, STScI, A. Pagan (STScI)

M76 is classified as a planetary nebula, an expanding shell of glowing gases that were ejected from a dying red giant star. The star eventually collapses to an ultra-dense and hot white dwarf. A planetary nebula is unrelated to planets, but has that name because astronomers in the 1700s using low-power telescopes thought this type of object resembled a planet.

M76 is composed of a ring, seen edge-on as the central bar structure, and two lobes on either opening of the ring. Before the star burned out, it ejected the ring of gas and dust. The ring was probably sculpted by the effects of the star that once had a binary companion star. This sloughed-off material created a thick disc of dust and gas along the plane of the companion’s orbit. The hypothetical companion star isn’t seen in the Hubble image, and so it could have been later swallowed by the central star. The disc would be forensic evidence for that stellar cannibalism.

The primary star is collapsing to form a white dwarf. It is one of the hottest stellar remnants known, at a scorching 120 000 degrees Celsius, 24 times our Sun’s surface temperature. 
The sizzling white dwarf can be seen as a pinpoint in the centre of the nebula. A star visible in projection beneath it is not part of the nebula.

Pinched off by the disc, two lobes of hot gas are escaping from the top and bottom of the ‘belt’ along the star’s rotation axis that is perpendicular to the disc. They are being propelled by the hurricane-like outflow of material from the dying star, tearing across space at two million miles per hour. That’s fast enough to travel from Earth to the Moon in a little over seven minutes! This torrential ‘stellar wind’ is ploughing into cooler, slower-moving gas that was ejected at an earlier stage in the star’s life, when it was a red giant. Ferocious ultraviolet radiation from the super-hot star is causing the gases to glow. The red colour is from nitrogen, and blue is from oxygen.

Given that our solar system is 4.6 billion years old, the entire nebula is a flash in the pan by cosmological timekeeping. It will vanish in about 15 000 years.


34 years of science and imagery

Since its launch in 1990 Hubble has made 1.6 million observations of over 53 000 astronomical objects. To date, the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute in Baltimore, Maryland holds 184 terabytes of processed data that are science-ready for use by astronomers around the world to use for research and analysis. A European mirror of the public data is hosted at ESA’s European Space Astronomy Centre (ESAC), in the European Hubble Space Telescope (eHST) Science Archive.

Since 1990, 44 000 science papers have been published from Hubble observations. This includes a record 1056 papers published in 2023, of which 409 were led by authors in the ESA Member States. The demand for using Hubble is so high it is currently oversubscribed by a factor of six.

Throughout its past year of science operations, new discoveries made using Hubble include finding water in the atmosphere of the smallest exoplanet to date, spotting a bizarre cosmic explosion far from any host galaxy, following spokes on the rings of Saturn and finding the unexpected home of the most distant and powerful fast radio burst yet seen. Hubble’s studies of the asteroid Dimorphos, the target of a deliberate NASA spacecraft collision in September 2022 to alter its trajectory, continued with the detection of boulders released by the impact.

Hubble has also continued to provide spectacular images of celestial targets including spiral galaxies, globular clusters and star-forming nebulae. A newly forming star was the source of a cosmic light show. Hubble imagery was also combined with infrared observations from the NASA/ESA/CSA James Webb Space Telescope to create one of the most comprehensive views of the Universe ever, an image of galaxy cluster MACS 0416.

Most of Hubble’s discoveries were not anticipated before launch, such as supermassive black holes, the atmospheres of exoplanets, gravitational lensing by dark matter, the presence of dark energy, and the abundance of planet formation among stars. Hubble will continue research in those domains, as well as capitalising on its unique ultraviolet-light capability to examine such things as Solar System phenomena, supernova outbursts, the composition of exoplanet atmospheres, and dynamic emission from galaxies. And Hubble investigations continue to benefit from its long baseline of observations of Solar System objects, variable stellar phenomena and other exotic astrophysics of the cosmos.

The performance characteristics of the James Webb Space Telescope were designed to be uniquely complementary to Hubble, and not a substitute. Future Hubble research also will take advantage of the opportunity for synergies with Webb, which observes the Universe in infrared light. Combined together, the complementary wavelength coverage of the two space telescopes expands on groundbreaking research in such areas as protostellar discs, exoplanet composition, unusual supernovae, cores of galaxies and chemistry of the distant Universe.

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.

Annotated image labeled “Little Dumbbell Nebula, M76, HST WFC3/UVIS” against the black background of space. Near top left, a color key consisting of five lines reads: “F475W SDSS g’” in light blue; “F502N OIII” in dark blue; “F656N Ha” in green; “F658N NIII” in red; and “F814W I” in orange. The nebula is located 3,400 light-years away in the northern circumpolar constellation Perseus. The name ‘Little Dumbbell’ comes from its shape that is a two-lobed structure of colorful, mottled, glowing gases resembling a balloon that’s been pinched around a middle waist. Like an inflating balloon, the lobes are expanding into space from a dying star seen as a white dot in the centre. Blistering ultraviolet radiation from the super-hot star is causing the gases to glow. The red color is from nitrogen, and blue is from oxygen. At bottom left corner is a scale bar labeled “1 light-year.” At bottom right corner, the “E” compass arrow points towards the 10 o’clock position. The “N” arrow points towards the 1 o’clock position.
In celebration of the 34th anniversary of the launch of the legendary NASA/ESA Hubble Space Telescope, astronomers took a snapshot of the Little Dumbbell Nebula (also known as Messier 76, M76, or NGC 650/651) located 3400 light-years away in the northern circumpolar constellation Perseus. The photogenic nebula is a favourite target of amateur astronomers.
M76 is classified as a planetary nebula. This is a misnomer because it is unrelated to planets. But its round shape suggested it was a planet to astronomers who first viewed it through low-power telescopes. In reality, a planetary nebula is an expanding shell of glowing gases that were ejected from a dying red giant star. The star eventually collapses to an ultra-dense, hot white dwarf.
M76 is composed of a ring, seen edge-on as the central bar structure, and two lobes on either opening of the ring. Before the star burned out, it ejected the ring of gas and dust. The ring was probably sculpted by the effects of the star that once had a binary companion star. This sloughed-off material created a thick disc of dust and gas along the plane of the companion’s orbit. The hypothetical companion star isn’t seen in the Hubble image, and so it could have been later swallowed by the central star. The disc would be forensic evidence for that stellar cannibalism.
The primary star is collapsing to form a white dwarf. It is one of the hottest stellar remnants known at a scorching 120 000 degrees Celsius, 24 times our Sun’s surface temperature. 
The sizzling white dwarf can be seen as a pinpoint in the centre of the nebula. A star visible in projection beneath it is not part of the nebula.


Pinched off by the disc, two lobes of hot gas are escaping from the top and bottom of the ‘belt’ along the star’s rotation axis that is perpendicular to the disc. They are being propelled by the hurricane-like outflow of material from the dying star, tearing across space at two million miles per hour. That’s fast enough to travel from Earth to the Moon in a little over seven minutes! This torrential ‘stellar wind’ is ploughing into cooler, slower-moving gas that was ejected at an earlier stage in the star’s life, when it was a red giant. Ferocious ultraviolet radiation from the super-hot star is causing the gases to glow. The red colour is from nitrogen, and blue is from oxygen.

The entire nebula is a flash in the pan by cosmological timekeeping. It will vanish in about 15 000 years.
Credit: NASA, ESA, STScI, A. Pagan (STScI)

Press release from ESA Hubble

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Hubble goes hunting for small main-belt asteroids

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This graph plots the size of asteroids versus their abundance, based on a Hubble Space Telescope archival survey that found 1701 mostly previously undetected asteroids lying between the orbits of Mars and Jupiter. The vertical axis lists the number of objects from zero to 70. The horizontal axis lists size, from zero kilometres on the left, to 2 kilometres on the right. The graph slopes up such that the most abundant asteroids detected by Hubble in the survey are 0.5 kilometres across in size.

Hubble goes hunting for small main-belt asteroids

Astronomers recently used a trove of archived images taken by the NASA/ESA Hubble Space Telescope to visually snag a largely unseen population of smaller asteroids in their tracks. The treasure hunt required pursuing 37 000 Hubble images spanning 19 years. The payoff was finding 1701 asteroid trails, with 1031 of those asteroids uncatalogued. About 400 of these uncatalogued asteroids are about below a kilometre in size.

Annotated image of barred spiral galaxy UGC 12158 against the black background of space, with compass arrows, a scale bar, and colour key for reference. The galaxy has a pinwheel shape made up of bright blue stars wound around a yellow-white hub of central stars. The galaxy is tilted face-on to our view from Earth. A slightly S-shaped white line across the top is the Hubble image of an asteroid streaking across Hubble’s view. Indicated filters are expressed as: “F475W” in blue, “F606W” in green, and “F814W” in red. At the bottom left corner is a scale bar labelled “60,000 light-years” over “30 arcseconds.” At the bottom right corner, the “E” compass arrow points towards the 2 o’clock position. The “N” compass arrow points towards the 5 o’clock position.
This is an annotated NASA/ESA Hubble Space Telescope image of the barred spiral galaxy UGC 12158, with compass arrows, a scale bar, and colour key for reference. It looks like someone took a white marking pen to it. In reality it is a combination of time exposures of a foreground asteroid moving through Hubble’s field of view, photobombing the observation of the galaxy. Several exposures of the galaxy were taken, which is evidenced by the dashed pattern.
The asteroid appears as a curved trail as a result of parallax: Hubble is not stationary, but orbiting Earth, and this gives the illusion that the faint asteroid is swimming along a curved trajectory. The uncharted asteroid is inside the asteroid belt in our Solar System, and hence is 10 trillion times closer to Hubble than the background galaxy.
Rather than being a nuisance, this type of data is useful to astronomers for doing a census of the asteroid population in our Solar System.
Credit: NASA, ESA, P. G. Martín (Autonomous University of Madrid), J. DePasquale (STScI).
Acknowledgment: A. Filippenko (University of California, Berkeley)

Volunteers from around the world known as ‘citizen scientists’ contributed to the identification of this asteroid bounty. Professional scientists combined the volunteers’ efforts with machine learning algorithms to identify the asteroids. This represents a new approach to finding asteroids in astronomical archives spanning decades, and it may be effectively applied to other datasets, say the researchers.

“We are getting deeper into seeing the smaller population of main-belt asteroids. We were surprised to see such a large number of candidate objects,” said lead author Pablo García Martín of the Autonomous University of Madrid, Spain. “There was some hint that this population existed, but now we are confirming it with a random asteroid population sample obtained using the whole Hubble archive. This is important for providing insights into the evolutionary models of our Solar System.”

The large, random sample offers new insights into the formation and evolution of the asteroid belt. Finding a lot of small asteroids favours the idea that they are fragments of larger asteroids that have collided and broken apart, like smashed pottery. This is a grinding-down process spanning billions of years.

This graph plots the size of asteroids versus their abundance, based on a Hubble Space Telescope archival survey that found 1701 mostly previously undetected asteroids lying between the orbits of Mars and Jupiter. The vertical axis lists the number of objects from zero to 70. The horizontal axis lists size, from zero kilometres on the left, to 2 kilometres on the right. The graph slopes up such that the most abundant asteroids detected by Hubble in the survey are 0.5 kilometres across in size.
This graph is based on Hubble Space Telescope archival data that were used to identify a largely unseen population of very small asteroids. The asteroids were not the intended targets, but instead photobombed background stars and galaxies in Hubble images. The comprehensive treasure hunt required perusing 37 000 Hubble images spanning 19 years. This was accomplished by using ‘citizen science’ volunteers and artificial intelligence algorithms. The payoff was finding 1701 trails of previously undetected asteroids.
Credit: NASA, ESA, P. G. Martín (Autonomous University of Madrid), E. Wheatley (STScI)

An alternative theory for the existence of smaller fragments is that they formed that way billions of years ago. But there is no conceivable mechanism that would keep them from snowballing up to larger sizes as they agglomerate dust from the planet-forming circumstellar disc around our Sun. “Collisions would have a certain signature that we can use to test the current main belt population,” said co-author Bruno Merín of the European Space Astronomy Centre in Madrid, Spain.

Because of Hubble’s fast orbit around Earth, it can capture wandering asteroids through their telltale trails in the Hubble exposures. As viewed from an Earth-based telescope, an asteroid leaves a streak across the picture. Asteroids ‘photobomb’ Hubble exposures by appearing as unmistakable, curved trails in Hubble photographs.

As Hubble moves around Earth, it changes its point of view while observing an asteroid, which also moves along its own orbit. By knowing Hubble’s position during the observation and measuring the curvature of the streaks, scientists can determine the distances to the asteroids and estimate the shapes of their orbits.

The asteroids snagged mostly dwell in the main belt, which lies between the orbits of Mars and Jupiter. Their brightness is measured by Hubble’s sensitive cameras, and comparing their brightness to their distance allows for a size estimate. The faintest asteroids in the survey are roughly one forty-millionth the brightness of the faintest star that can be seen by the human eye.

“Asteroid positions change with time, and therefore you cannot find them just by entering coordinates, because at different times they might not be there,” said Merín. “As astronomers we don’t have time to go looking through all the asteroid images. So we got the idea to collaborate with more than 10 000 citizen-science volunteers to peruse the huge Hubble archives.”

In 2019 an international group of astronomers launched the Hubble Asteroid Hunter, a citizen-science project to identify asteroids in archival Hubble data. The initiative was developed by researchers and engineers at the European Science and Technology Centre (ESTEC) and the European Space Astronomy Centre’s science data centre (ESDC), in collaboration with the Zooniverse platform, the world’s largest and most popular citizen-science platform, and Google.

A total of 11 482 citizen-science volunteers, who provided nearly two million identifications, were then given a training set for an automated algorithm to identify asteroids based on artificial intelligence. This pioneering approach may be effectively applied to other datasets.

The project will next explore the streaks of previously unknown asteroids to characterise their orbits and study their properties, such as rotation periods. Because most of these asteroid streaks were captured by Hubble many years ago, it is not possible to follow them up now to determine their orbits.

The findings are published in the journal Astronomy and Astrophysics.

This is a Hubble Space Telescope image of the barred spiral galaxy UGC 12158. The majestic galaxy has a pinwheel shape made up of bright blue stars wound around a yellow-white hub of central stars. The hub has a slash of stars across it, called a bar. The galaxy is tilted face-on to our view from Earth. A slightly S-shaped white line across the top is the Hubble image of an asteroid streaking across Hubble’s view. It looks dashed because the image is a combination of several exposures of the asteroid flying by like a race car.
This NASA/ESA Hubble Space Telescope image of the barred spiral galaxy UGC 12158 looks like someone took a white marking pen to it. In reality it is a combination of time exposures of a foreground asteroid moving through Hubble’s field of view, photobombing the observation of the galaxy. Several exposures of the galaxy were taken, which is evidenced by the dashed pattern.
The asteroid appears as a curved trail as a result of parallax: Hubble is not stationary, but orbiting Earth, and this gives the illusion that the faint asteroid is swimming along a curved trajectory. The uncharted asteroid is inside the asteroid belt in our Solar System, and hence is 10 trillion times closer to Hubble than the background galaxy.
Rather than being a nuisance, this type of data is useful to astronomers for doing a census of the asteroid population in our Solar System.
Credit: NASA, ESA, P. G. Martín (Autonomous University of Madrid), J. DePasquale (STScI).
Acknowledgment: A. Filippenko (University of California, Berkeley)

Press release from ESA Hubble

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Webb probes Messier 82 (M82), an extreme starburst galaxy

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Left: Messier 82 as imaged by Hubble. Hour-glass-shaped red plumes of gas are shooting outward from above and below a bright blue, disc-shaped centre of a galaxy. This galaxy is surrounded by many white stars and set against the black background of space. Right: A section of Messier 82 as imaged by Webb. An edge-on spiral starburst galaxy with a bright white, glowing core set against the black background of space. A white band of the edge-on disc extends from lower left to upper right. Dark brown tendrils of dust are scattered thinly along this band. Many clumpy, red filaments extend vertically above and below the plane of the galaxy.

Webb probes Messier 82 (M82), an extreme starburst galaxy

Amid a galaxy teeming with new and young stars lies an intricate substructure

Left: Messier 82 as imaged by Hubble. Hour-glass-shaped red plumes of gas are shooting outward from above and below a bright blue, disc-shaped centre of a galaxy. This galaxy is surrounded by many white stars and set against the black background of space. Right: A section of Messier 82 as imaged by Webb. An edge-on spiral starburst galaxy with a bright white, glowing core set against the black background of space. A white band of the edge-on disc extends from lower left to upper right. Dark brown tendrils of dust are scattered thinly along this band. Many clumpy, red filaments extend vertically above and below the plane of the galaxy.
Annotated image of the starburst galaxy Messier 82 captured by Webb’s NIRCam (Near-Infrared Camera) instrument, with compass arrows, a scale bar, and colour key for reference.
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).
The scale bar is labelled in light-years.
This image shows invisible near-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which NIRCam filters were used when collecting the light. The colour of each filter name is the visible light colour used to represent the infrared light that passes through that filter.
Credit: NASA, ESA, CSA, STScI, A. Bolatto (UMD)

The NASA/ESA/CSA James Webb Space Telescope has set its sights on the starburst galaxy Messier 82 (M82), a small but mighty environment that features rapid star formation. By looking closer with Webb’s sensitive infrared capabilities, a team of scientists is getting to the very core of the galaxy, gaining a better understanding of how it is forming stars and how this extreme activity is affecting the galaxy as a whole.

An international team of astronomers has used the NASA/ESA/CSA James Webb Space Telescope to survey the starburst galaxy Messier 82 (M82). Located 12 million light-years away in the constellation Ursa Major, this galaxy is relatively compact in size but hosts a frenzy of star formation activity. For comparison, M82 is sprouting new stars 10 times faster than the Milky Way galaxy.

The team directed Webb’s NIRCam (Near-Infrared Camera) instrument toward the starburst galaxy’s centre, obtaining a closer look at the physical conditions that foster the formation of new stars.

“M82 has garnered a variety of observations over the years because it can be considered as the prototypical starburst galaxy,” said Alberto Bolatto, lead author of the study. “Both Spitzer and Hubble space telescopes have observed this target. With Webb’s size and resolution, we can look at this star-forming galaxy and see all of this beautiful new detail.”

Star formation continues to maintain a sense of mystery because it is shrouded by curtains of dust and gas, creating an obstacle to observing this process. Fortunately, Webb’s ability to peer in the infrared is an asset in navigating these murky conditions. Additionally, these NIRCam images of the very centre of the starburst were obtained using an instrument mode that prevented the very bright source from overwhelming the detector.

An edge-on spiral starburst galaxy with a bright white, glowing core set against the black background of space. A white band of the edge-on disc extends from lower left to upper right. Dark brown tendrils of dust are scattered thinly along this band. Many white points in various sizes — stars or star clusters — are scattered throughout the image, but are most heavily concentrated toward the centre. Many clumpy, red filaments extend vertically above and below the plane of the galaxy.
Astronomers used the NASA/ESA/CSA James Webb Space Telescope to look toward M82’s centre, where a galactic wind is being launched as a result of rapid star formation and subsequent supernovae. Studying the galactic wind can offer insight into how the loss of gas shapes the future growth of the galaxy.
This image from Webb’s NIRCam (Near-Infrared Camera) instrument shows M82’s galactic wind via emission from sooty chemical molecules known as polycyclic aromatic hydrocarbons (PAHs). PAHs are very small dust grains that survive in cooler temperatures but are destroyed in hot conditions. The structure of the emission resembles that of hot, ionised gas, suggesting PAHs may be replenished by continued ionisation of molecular gas.
In this image, light at 3.35 microns is coloured red, 2.50 microns is green, and 1.64 microns is blue (filters F335M, F250M, and F164N, respectively).
Credit: NASA, ESA, CSA, STScI, A. Bolatto (UMD)

While dark brown tendrils of dust are threaded throughout M82’s glowing white core even in this infrared view, Webb’s NIRCam has revealed a level of detail that has historically been obscured. Looking closer toward the centre, small specks depicted in green denote concentrated areas of iron, most of which are supernova remnants. Small patches that appear red signify regions where molecular hydrogen is being lit up by the radiation from a nearby young star.

“This image shows the power of Webb,” said Rebecca Levy, second author of the study, at the University of Arizona in Tucson. “Every single white dot in this image is either a star or a star cluster. We can start to distinguish all of these tiny point sources, which enables us to acquire an accurate count of all the star clusters in this galaxy.”

Looking at M82 in slightly longer infrared wavelengths, clumpy tendrils represented in red can be seen extending above and below the plane of the galaxy. These gaseous streamers are a galactic wind rushing out from the core of the starburst.

One area of focus for this research team was understanding how this galactic wind, which is caused by the rapid rate of star formation and subsequent supernovae, is being launched and influencing its surrounding environment. By resolving a central section of M82, scientists have been able to examine where the wind originates, and gain insight into how hot and cold components interact within the wind.

A section of M82 as imaged by Webb. An edge-on spiral starburst galaxy with a bright white, glowing core set against the black background of space. Dark brown tendrils of dust are scattered heavily toward the galaxy’s centre. Many white points in various sizes — stars or star clusters — are scattered throughout the image, but are most heavily concentrated toward the centre.
A team of astronomers used the NASA/ESA/CSA James Webb Space Telescope to survey the starburst galaxy Messier 82 (M82), which is located 12 million light-years away in the constellation Ursa Major. M82 hosts a frenzy of star formation, sprouting new stars 10 times faster than the Milky Way galaxy. Webb’s infrared capabilities enabled scientists to peer through curtains of dust and gas that have historically obscured the star formation process.
This image from Webb’s NIRCam (Near-Infrared Camera) instrument shows the centre of M82 with an unprecedented level of detail. With Webb’s resolution, astronomers can distinguish small, bright compact sources that are either individual stars or star clusters. Obtaining an accurate count of the stars and clusters that compose M82’s centre can help astronomers understand the different phases of star formation and the timelines for each stage.
In this image, light at 2.12 microns is coloured red, 1.64 microns is green, and 1.40 microns is blue (filters F212N, 164N, and F140M, respectively).
Credit: NASA, ESA, CSA, STScI, A. Bolatto (UMD)

Webb’s NIRCam instrument was well suited to tracing the structure of the galactic wind via emission from sooty chemical molecules known as polycyclic aromatic hydrocarbons (PAHs). PAHs can be considered as very small dust grains that survive in cooler temperatures but are destroyed in hot conditions.

Much to the team’s surprise, Webb’s view of the PAH emission highlights the galactic wind’s fine structure — an aspect previously unknown. Depicted as red filaments, the emission extends away from the central region where the heart of star formation is located. Another unanticipated find was the similarity between the structure of the PAH emission and that of the hot, ionised gas.

“It was unexpected to see the PAH emission resemble ionised gas,” said Bolatto. “PAHs are not supposed to live very long when exposed to such a strong radiation field, so perhaps they are being replenished all the time. It challenges our theories and shows us that further investigation is required.”

Webb’s observations of M82 in near-infrared light also spur further questions about star formation, some of which the team hopes to answer with additional data gathered with Webb, including that of another starburst galaxy. Two other papers from this team characterising the stellar clusters and correlations among wind components of M82 are almost finalised.

Left: Messier 82 as imaged by Hubble. Hour-glass-shaped red plumes of gas are shooting outward from above and below a bright blue, disc-shaped centre of a galaxy. This galaxy is surrounded by many white stars and set against the black background of space. Right: A section of Messier 82 as imaged by Webb. An edge-on spiral starburst galaxy with a bright white, glowing core set against the black background of space. A white band of the edge-on disc extends from lower left to upper right. Dark brown tendrils of dust are scattered thinly along this band. Many clumpy, red filaments extend vertically above and below the plane of the galaxy.
The starburst galaxy M82 was observed by the NASA/ESA Hubble Space Telescope in 2006, which showed the galaxy’s edge-on spiral disc, shredded clouds, and hot hydrogen gas. The NASA/ESA/CSA James Webb Space Telescope has observed M82’s core, capturing in unprecedented detail the structure of the galactic wind and characterising individual stars and star clusters.
The Webb image is from the telescope’s NIRCam (Near-Infrared Camera) instrument. The red filaments trace the shape of the cool component of the galactic wind via polycyclic aromatic hydrocarbons (PAHs). PAHs are very small dust grains that survive in cooler temperatures but are destroyed in hot conditions. The structure of the emission is similar to that of the ionised gas, suggesting PAHs may be replenished from cooler molecular material as it is ionised.
Credit: NASA, ESA, CSA, STScI, A. Bolatto (UMD)

In the near future, the team will have spectroscopic observations of M82 from Webb ready for their analysis, as well as complementary large-scale images of the galaxy and its wind. Spectral data will help astronomers determine accurate ages for the star clusters and provide a sense of how long each phase of star formation lasts in a starburst galaxy environment. On a broader scale, inspecting the activity in galaxies like M82 can deepen astronomers’ understanding of the early Universe.

“With these amazing Webb images, and our upcoming spectra, we can study how exactly the strong winds and shock fronts from young stars and supernovae can remove the very gas and dust from which new stars are forming,” said Torsten Böker of the European Space Agency, a co-author of the study. “A detailed understanding of this ‘feedback’ cycle is important for theories of how the early Universe evolved, because compact starbursts such as the one in M82 were very common at high redshift.”

These findings have been accepted for publication in The Astrophysical Journal.

 

Press release from ESA Webb.

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Hubble sees FS Tau B, likely in the process of becoming a T Tauri star

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FS Tau B A bright point of light shines near center-right with diffraction spikes, surrounded by glowing clouds against black space. A blue jet of material extends roughly throughout the center of the image, partially obscured by the clouds.

Hubble sees FS Tau B, likely in the process of becoming a T Tauri star

Jets emerge from the cocoon of a newly forming star to blast across space, slicing through the gas and dust of a shining nebula, in this new image from the NASA/ESA Hubble Space Telescope.

A bright point of light shines near center-right with diffraction spikes, surrounded by glowing clouds against black space. A blue jet of material extends roughly throughout the center of the image, partially obscured by the clouds.
FS Tau is a multi-star system made up of FS Tau A, the bright star-like object near the middle of the image, and FS Tau B (Haro 6-5B), the bright object to the far right that is partially obscured by a dark, vertical lane of dust. The young objects are surrounded by softly illuminated gas and dust of this stellar nursery. The system is only about 2.8 million years old, very young for a star system. Our Sun, by contrast, is about 4.6 billion years old.
FS Tau B is a newly forming star, or protostar, and is surrounded by a protoplanetary disc, a pancake-shaped collection of dust and gas leftover from the formation of the star that will eventually coalesce into planets. The thick dust lane, seen nearly edge-on, separates what are thought to be the illuminated surfaces of the disc.
FS Tau B is likely in the process of becoming a T Tauri star, a type of young variable star that hasn’t begun nuclear fusion yet but is beginning to evolve into a hydrogen-fueled star similar to our Sun. Protostars shine with the heat energy released as the gas clouds from which they are forming collapse, and from the accretion of material from nearby gas and dust. Variable stars are a class of star whose brightness changes noticeably over time.
FS Tau A is itself a T Tauri binary system, consisting of two stars orbiting each other.
Protostars are known to eject fast-moving, column-like streams of energised material called jets, and FS Tau B provides a striking example of this phenomenon. The protostar is the source of an unusual asymmetric, double-sided jet, visible here in blue. Its asymmetrical structure may be because mass is being expelled from the object at different rates.
FS Tau B is also classified as a Herbig-Haro object. Herbig–Haro objects form when jets of ionised gas ejected by a young star collide with nearby clouds of gas and dust at high speeds, creating bright patches of nebulosity.
FS Tau is part of the Taurus-Auriga region, a collection of dark molecular clouds that are home to numerous newly forming and young stars, roughly 450 light-years away in the constellations of Taurus and Auriga. Hubble has previously observed this region, whose star-forming activity makes it a compelling target for astronomers. Hubble made these observations as part of an investigation of edge-on dust discs around young stellar objects.
Credit: NASA, ESA, K. Stapelfeldt (NASA JPL), G. Kober (NASA/Catholic University of America)

FS Tau is a multi-star system made up of FS Tau A, the bright star-like object near the middle of the image, and FS Tau B (Haro 6-5B), the bright object to the far right that is partially obscured by a dark, vertical lane of dust. These young objects are surrounded by the softly illuminated gas and dust of this stellar nursery. The system is only about 2.8 million years old, very young for a star system. Our Sun, by contrast, is about 4.6 billion years old.

FS Tau B is a newly forming star, or protostar, and is surrounded by a protoplanetary disc, a pancake-shaped collection of dust and gas left over from the formation of the star that will eventually coalesce into planets. The thick dust lane, seen nearly edge-on, separates what are thought to be the illuminated surfaces of the disc.

FS Tau B is likely in the process of becoming a T Tauri star, a type of young variable star that hasn’t begun nuclear fusion yet but is beginning to evolve into a hydrogen-fueled star similar to our Sun. Protostars shine with the heat energy released as the gas clouds from which they are forming collapse, and from the accretion of material from nearby gas and dust. Variable stars are a class of star whose brightness changes noticeably over time.

FS Tau A is itself a T Tauri binary system, consisting of two stars orbiting each other.

Protostars are known to eject fast-moving, column-like streams of energised material called jets, and FS Tau B provides a striking example of this phenomenon. The protostar is the source of an unusual asymmetric, double-sided jet, visible here in blue. Its asymmetrical structure may be because mass is being expelled from the object at different rates.

FS Tau B is also classified as a Herbig-Haro object. Herbig–Haro objects form when jets of ionised gas ejected by a young star collide with nearby clouds of gas and dust at high speeds, creating bright patches of nebulosity.

FS Tau is part of the Taurus-Auriga region, a collection of dark molecular clouds that are home to numerous newly forming and young stars, roughly 450 light-years away in the constellations of Taurus and Auriga. Hubble has previously observed this region, whose star-forming activity makes it a compelling target for astronomers. Hubble made these observations as part of an investigation of edge-on dust discs around young stellar objects.

Press release from ESA Hubble.

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Hubble finds that ageing brown dwarfs grow lonely

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brown dwarfs once paired This artist’s representation shows a brown dwarf, an object more massive than a planet but smaller than a star. The dwarf is a cherry-red sphere. It has horizontal stripes of various shades of red that are cloud bands. In the dark background there are myriad stars that are inside our Milky Way galaxy.

Hubble finds that ageing brown dwarfs grow lonely: for the ones that were once paired, that’s a relationship that doesn’t last long

It takes two to tango, but in the case of brown dwarfs that were once paired as binary systems, that relationship doesn’t last for very long, according to a recent survey using the NASA/ESA Hubble Space Telescope.

This artist’s representation shows a brown dwarf, an object more massive than a planet but smaller than a star. The dwarf is a cherry-red sphere. It has horizontal stripes of various shades of red that are cloud bands. In the dark background there are myriad stars that are inside our Milky Way galaxy.
This is an artist’s representation of a brown dwarf. This class of object is too large to be a planet (and did not form in the same way), but is too small to be a star because it cannot sustain nuclear fusion, since it is less massive than even the smallest stars. A brown dwarf is likely to be marked by wind-driven horizontal bands of thick clouds that may alternate with relatively cloud-free bands, giving the object a striped appearance. Whirling storm systems as big as terrestrial continents, or even small planets, might exist.
The name ‘brown dwarf’ is actually a misnomer because the object would typically appear red to the naked eye. It is brightest in infrared light. Many brown dwarfs have binary companions. But as they age, the binary system drifts apart and each dwarf goes its separate way, according to a recent Hubble Space Telescope study.
The background stars in this illustration are a science visualisation assembled from the Gaia spacecraft star catalogue. The synthesised stars are accurate in terms of position, brightness, and colour. Because this is not an image of the Milky Way, missing are glowing nebulae and dark dust clouds.
Credit: NASA, ESA, J. Olmsted (STScI)

Brown dwarfs are interstellar objects larger than Jupiter but smaller than the lowest-mass stars. Like stars, they collapse out of a cloud of gas and dust but do not have enough mass to sustain the fusion of hydrogen like a normal star.

Like stars, brown dwarfs can be born in pairs and orbit about each other. A Hubble Space Telescope survey has found that the older a brown dwarf is, the less likely it is to have a companion dwarf. This implies that a binary pair of dwarfs is so weakly linked by gravity that they drift apart over a few hundred million years as a result of the pull of bypassing stars. Call them the lonely hearts of the cosmos.

Hubble can detect binaries as close to each other as 480 million kilometres — the approximate separation between our Sun and the asteroid belt. But the astronomers who carried out the survey didn’t find any binary pairs in a sample of brown dwarfs in the solar neighbourhood.

“Our survey confirms that widely separated companions are extremely rare among the lowest-mass and coldest isolated brown dwarfs, even though binary brown dwarfs are observed at younger ages. This suggests that such systems do not survive over time,” said lead author Clémence Fontanive of the Trottier Institute for Research on Exoplanets, University of Montreal, Canada.

In a similar survey Fontanive conducted a couple of years ago, Hubble looked at extremely young brown dwarfs and some had binary companions, confirming that star-forming mechanisms do produce binary pairs among low-mass brown dwarfs. The lack of binary companions for older brown dwarfs suggests that some may have started out as binaries, but parted ways over time.

The new Hubble findings further support the theory that brown dwarfs are born the same way as stars, through the gravitational collapse of a cloud of molecular hydrogen. The difference is that they do not have enough mass to sustain nuclear fusion of hydrogen for generating energy, whereas stars do. More than half of the stars in our galaxy have a companion star that resulted from these formation processes, with more massive stars more commonly found in binary systems. “The motivation for the study was really to see how low in mass the trends seen among multiple star systems hold up,” said Fontanive.

“Our Hubble survey offers direct evidence that these binaries that we observe when they’re young are unlikely to survive to old ages, they’re likely going to get disrupted. When they’re young, they’re part of a molecular cloud, and then as they age the cloud disperses. As that happens, things start moving around and stars pass by each other. Because brown dwarfs are so light, the gravitational hold tying wide binary pairs is very weak, and bypassing stars can easily tear these binaries apart,” said Fontanive.

The team selected a sample of brown dwarfs previously identified by NASA’s Wide-Field Infrared Survey Explorer. It sampled some of the coldest and lowest-mass old brown dwarfs in the solar neighbourhood. These old brown dwarfs are so cool (a few hundred degrees warmer than Jupiter in most cases) that their atmospheres contain water vapour that condensed out.

To find the coolest companions, the team used two different near-infrared filters, one in which cold brown dwarfs are bright, and another covering specific wavelengths where they appear very faint as a result of water absorption in their atmospheres.

“Most stars have friends – whether that is a binary companion or exoplanets,” added team member Beth Biller of the University of Edinburgh in the United Kingdom. “This survey really demonstrates that the same is not true for brown dwarfs. After a brief period early in their lifespans, most brown dwarfs remain single for the rest of their very long existence.”

“This is the best observational evidence to date that brown dwarf pairs drift apart over time,” said Fontanive. “We could not have done this kind of survey and confirmed earlier models without Hubble’s sharp vision and sensitivity.”

 

Press release from ESA Hubble.

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Hubble tracks the stormy weather on Jupiter

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stormy weather Jupiter A side-by-side image showing both faces of Jupiter on the black background of space. The left image is labelled January 5, 2024. Jupiter is banded with stripes of brownish orange, light grey, soft yellow, and shades of cream, punctuated with many large storms and small white clouds. The Great Red Spot is the most prominent feature in the left bottom third of this view. The right image is labelled January 6, 2024. This opposite side of Jupiter is also banded with stripes of brownish orange, light grey, soft yellow, and shades of cream. At upper right of centre, a pair of storms appear next to each other: a deep-red, triangle-shaped cyclone and a reddish anticyclone. Toward the far-left edge of this view is Jupiter’s tiny orange-coloured moon Io.

Hubble tracks the stormy weather on Jupiter

 

The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in these latest images, taken on 5–6 January 2024, that capture both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.

The largest and nearest of the giant outer planets, Jupiter’s colourful clouds present an ever-changing kaleidoscope of shapes and colours. This is a planet where there is always stormy weather: cyclones, anticyclones, wind shear, and the largest storm in the Solar System, the Great Red Spot. Jupiter has no solid surface and is perpetually covered with largely ammonia ice-crystal clouds that are only about 48 kilometres thick in an atmosphere that’s tens of thousands of kilometres deep and give the planet its banded appearance. The bands are produced by air flowing in different directions at various latitudes with speeds approaching 560 kilometres per hour. Lighter-hued areas where the atmosphere rises are called zones. Darker regions where air falls are called belts. When these opposing flows interact, storms and turbulence appear. Hubble tracks these dynamic changes every year with unprecedented clarity, and there are always surprises. The many large storms and small white clouds seen in Hubble’s latest images are evidence for a lot of activity going on in Jupiter’s atmosphere right now.

 

 

Press release from ESA Hubble.

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Webb finds complex organic molecules in early-stage protostars

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A region of a molecular cloud. The cloud is dense and bright close to the top of the image, like rolling clouds, and grows darker and more wispy towards the bottom and in the top corner. One bright star, and several dimmer stars, are visible as light spots among the clouds. The image is a single exposure which has been assigned an orange colour for visibility.

Cheers! Webb finds complex organic molecules (COMs), such as ethanol and other icy ingredients for worlds, in early-stage protostars

An international team of astronomers using the NASA/ESA/CSA James Webb Space Telescope have discovered a variety of molecules, ranging from relatively simple ones like methane to complex compounds like acetic acid and ethanol, in early-stage protostars where planets have not yet formed. These are key ingredients for making potentially habitable worlds.

The presence of complex organic molecules (COMs) [1] in the solid phase in protostars was first predicted decades ago from laboratory experiments, and tentative detections of these molecules have been made by other space telescopes. This includes Webb’s Early Release Science Ice Age programme, which discovered diverse ices in the darkest, coldest regions of a molecular cloud measured to date.

A region of a molecular cloud. The cloud is dense and bright close to the top of the image, like rolling clouds, and grows darker and more wispy towards the bottom and in the top corner. One bright star, and several dimmer stars, are visible as light spots among the clouds. The image is a single exposure which has been assigned an orange colour for visibility.
This image was taken by Webb’s Mid-InfraRed Instrument (MIRI) of a region parallel to the massive protostar known as IRAS23385.
IRAS 2A and IRAS23385 (not visible in this image) were targets for a recent research effort by an international team of astronomers that used Webb to discover that the key ingredients for making potentially habitable worlds are present in early-stage protostars, where planets have not yet formed.
With MIRI’s unprecedented spectral resolution and sensitivity, the JOYS+ (James Webb Observations of Young ProtoStars) programme individually identified organic molecules that have been confirmed to be present in interstellar ices. This includes the robust detection of acetaldehyde, ethanol, methyl formate, and likely acetic acid, in the solid phase.
Credit: ESA/Webb, NASA, CSA, W. Rocha et al. (Leiden University)

Now, with the unprecedented spectral resolution and sensitivity of Webb’s Mid-InfraRed Instrument (MIRI), as part of the JOYS+ (James Webb Observations of Young ProtoStars) programme, these COMs have been individually identified and confirmed to be present in the interstellar ices. This includes the robust detection of acetaldehyde, ethanol (what we call alcohol), methyl formate, and likely acetic acid (the acid in vinegar), in the solid phase.

“This finding contributes to one of the long-standing questions in astrochemistry,” said team leader Will Rocha of Leiden University in the Netherlands. “What is the origin of COMs in space? Are they made in the gas phase or in ices? The detection of COMs in ices suggests that solid-phase chemical reactions on the surfaces of cold dust grains can build complex kinds of molecules.”

An international team of scientists using the NASA/ESA/CSA James Webb Space Telescope has identified a wealth of complex, carbon-containing (organic) molecules surrounding two protostars. This graphic shows the spectrum of one of the two protostars, IRAS 2A. It includes the fingerprints of acetaldehyde, ethanol, methylformate, and likely acetic acid, in the solid phase. These and other molecules detected there by Webb represent key ingredients for making potentially habitable worlds.Credit: NASA, ESA, CSA, L. Hustak (STScI)
An international team of scientists using the NASA/ESA/CSA James Webb Space Telescope has identified a wealth of complex, carbon-containing (organic) molecules surrounding two protostars. This graphic shows the spectrum of one of the two protostars, IRAS 2A. It includes the fingerprints of acetaldehyde, ethanol, methylformate, and likely acetic acid, in the solid phase. These and other molecules detected there by Webb represent key ingredients for making potentially habitable worlds.
Credit: NASA, ESA, CSA, L. Hustak (STScI)

As several COMs, including those detected in the solid phase in this research, were previously detected in the warm gas phase, it is now believed that they originate from the sublimation of ices. Sublimation is to change directly from a solid to a gas without becoming a liquid. Therefore, detecting COMs in ices makes astronomers hopeful about developing an improved understanding of the origins of other even larger molecules in space.

Harold Linnartz [2] led the Laboratory for Astrophysics in Leiden over many years and coordinated the measurements of the data used in this study. Ewine van Dishoeck of Leiden University, one of the coordinators of the JOYS+ programme, shared,

“Harold was particularly happy that in the COM assignments lab work could play an important role as it has been a long time getting here.”

Scientists are also keen to explore to what extent these COMs are transported to planets at much later stages in the evolution of the protostar. COMs in ices are transported more efficiently into planet-forming discs than gas from clouds. These icy COMs can therefore be inherited by comets and asteroids which in turn may collide with planets in formation. In that scenario COMs can be delivered to those planets, potentially providing the ingredients for life to flourish.

The science team also detected simpler molecules, including methane, formic acid (which makes the sting of ants painful), sulphur dioxide, and formaldehyde. Sulphur dioxide in particular allows the team to investigate the sulphur budget available in protostars. In addition, it is of prebiotic interest because existing research suggests that sulphur-containing compounds played an important role in driving metabolic reactions on the primitive Earth. Negative ions were also detected [3]; they form part of salts that are crucial for developing further chemical complexity at higher temperatures. This indicates that the ices may be much more complex and require further research.

Of particular interest is that one of the sources investigated, IRAS 2A, is characterised as a low-mass protostar. IRAS 2A may therefore have similarities with the primordial stages of our own Solar System. If that is the case, the chemical species identified in this protostar may have been present in the first stages of development of our Solar System and were later delivered to the primitive Earth.

All of these molecules can become part of comets and asteroids and eventually new planetary systems when the icy material is transported inward to the planet-forming discs as the protostellar system evolves,” said van Dishoeck. “We look forward to following this astrochemical trail step by step with more Webb data in the coming years.”

Other recent work by Pooneh Nazari of Leiden Observatory also raises astronomers’ hopes for finding more complexity in ices, following the tentative detections of methyl cyanide and ethyl cyanide from Webb NIRSpec data. Nazari says,

“It is impressive how Webb now allows us to further probe the ice chemistry down to the level of cyanides, important ingredients in prebiotic chemistry.”

 

Notes

[1] A molecule is a particle made up of two or more atoms that are held together by chemical bonds. A complex organic molecule is a molecule with multiple carbon atoms.

[2] These results are dedicated to team member Professor Harold Linnartz, who unexpectedly passed away in December 2023, shortly after the acceptance of this paper. Linnartz made significant contributions to the study of gaseous and icy molecules in space. He was the Director of the Leiden Laboratory for Astrophysics and many of the ice-phase spectra of simple and complex molecules used in this research were collected by students under his supervision. Linnartz was thrilled with the quality of the Webb data and the significance of these results for astrochemistry.

[3] An ion is an atom or molecule that has an overall electrical charge, resulting from an excess or deficit in the number of negative electrons compared to the number of positive protons in the ion. A negative ion is an ion with a net negative charge (so a surplus of electrons).

 

Press release from ESA Webb.

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Webb and Hubble telescopes affirm Universe’s expansion rate, puzzle persists

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A face-on spiral galaxy with four spiral arms that curve outward in a counterclockwise direction. The spiral arms are filled with young, blue stars and peppered with purplish star-forming regions that appear as small blobs. The middle of the galaxy is much brighter and more yellowish, and has a distinct narrow linear bar angled from 11 o’clock to 5 o’clock. Dozens of red background galaxies are scattered across the image. The background of space is black.

Webb and Hubble telescopes affirm Universe’s expansion rate, puzzle persists

Webb measurements shed new light on a decade-long mystery.

The rate at which the Universe is expanding, known as the Hubble constant, is one of the fundamental parameters for understanding the evolution and ultimate fate of the cosmos. However, a persistent difference, called the Hubble Tension, is seen between the value of the constant measured with a wide range of independent distance indicators and its value predicted from the afterglow of the Big Bang. The NASA/ESA/CSA James Webb Space Telescope has confirmed that the Hubble Space Telescope’s keen eye was right all along, erasing any lingering doubt about Hubble’s measurements.

One of the scientific justifications for building the NASA/ESA Hubble Space Telescope was to use its observing power to provide an exact value for the expansion rate of the Universe. Prior to Hubble’s launch in 1990, observations from ground-based telescopes yielded huge uncertainties. Depending on the values deduced for the expansion rate, the Universe could be anywhere between 10 and 20 billion years old. Over the past 34 years Hubble has shrunk this measurement to an accuracy of less than one percent, splitting the difference with an age value of 13.8 billion years. This has been accomplished by refining the so-called ‘cosmic distance ladder’ by measuring important milepost markers known as Cepheid variable stars.

A horizontal two-panel image of pixelated, black-and-white star fields. The left image is labelled Webb Near-IR and has a few dozen points of light of varying brightness. At the centre of the image, one bright point is circled. The right image is labelled Hubble Near-IR and has more indistinct, blurry patches whose overall brightness is similar to the more defined regions in the left image. At the centre, a light grey pixel is circled.
At the centre of these side-by-side images is a special class of star used as a milepost marker for measuring the Universe’s rate of expansion — a Cepheid variable star. The two images are very pixelated because each is a very zoomed-in view of a distant galaxy. Each of the pixels represents one or more stars. The image from the James Webb Space Telescope is significantly sharper at near-infrared wavelengths than Hubble (which is primarily a visible-ultraviolet light telescope). By reducing the clutter with Webb’s crisper vision, the Cepheid stands out more clearly, eliminating any potential confusion. Webb was used to look at a sample of Cepheids and confirmed the accuracy of the previous Hubble observations that are fundamental to precisely measuring the Universe’s expansion rate and age.
Credit: NASA, ESA, CSA, STScI, A. Riess (JHU/STScI)

However, the Hubble value does not agree with other measurements that imply that the Universe was expanding faster after the Big Bang. These observations were made by the ESA Planck satellite’s mapping of the cosmic microwave background radiation — a blueprint for how the Universe would evolve structure after it cooled down from the Big Bang.

The simple solution to the dilemma would be to say that maybe the Hubble observations are wrong, as a rresult of some inaccuracy creeping into its measurements of the deep-space yardsticks. Then along came the James Webb Space Telescope, enabling astronomers to crosscheck Hubble’s results. Webb’s infrared views of Cepheids agreed with Hubble’s optical-light data. Webb confirmed that the Hubble telescope’s keen eye was right all along, erasing any lingering doubt about Hubble’s measurements.

The bottom line is that the so-called Hubble Tension between what happens in the nearby Universe compared to the early Universe’s expansion remains a nagging puzzle for cosmologists. There may be something woven into the fabric of space that we don’t yet understand.

Does resolving this discrepancy require new physics? Or is it a result of measurement errors between the two different methods used to determine the rate of expansion of space?

Hubble and Webb have now tag-teamed to produce definitive measurements, furthering the case that something else — not measurement errors — is influencing the expansion rate.

“With measurement errors negated, what remains is the real and exciting possibility that we have misunderstood the Universe,” 

said Adam Riess, a physicist at Johns Hopkins University in Baltimore. Riess holds a Nobel Prize for co-discovering the fact that the Universe’s expansion is accelerating, owing to a mysterious phenomenon now called ‘dark energy’.

As a crosscheck, an initial Webb observation in 2023 confirmed that Hubble’s measurements of the expanding Universe were accurate. However, hoping to relieve the Hubble Tension, some scientists speculated that unseen errors in the measurement may grow and become visible as we look deeper into the Universe. In particular, stellar crowding could affect brightness measurements of more distant stars in a systematic way.

The SH0ES (Supernova H0 for the Equation of State of Dark Energy) team, led by Riess, obtained additional observations with Webb of objects that are critical cosmic milepost markers, known as Cepheid variable stars, which can now be correlated with the Hubble data.

“We’ve now spanned the whole range of what Hubble observed, and we can rule out a measurement error as the cause of the Hubble Tension with very high confidence,” Riess said.

The team’s first few Webb observations in 2023 were successful in showing Hubble was on the right track in firmly establishing the fidelity of the first rungs of the so-called cosmic distance ladder.

Astronomers use various methods to measure relative distances in the Universe, depending upon the object being observed. Collectively these techniques are known as the cosmic distance ladder — each rung or measurement technique relies upon the previous step for calibration.

But some astronomers suggested that, moving outward along the ‘second rung’, the cosmic distance ladder might get shaky if the Cepheid measurements become less accurate with distance. Such inaccuracies could occur because the light of a Cepheid could blend with that of an adjacent star — an effect that could become more pronounced with distance as stars crowd together on the sky and become harder to distinguish from one another.

The observational challenge is that past Hubble images of these more distant Cepheid variables look more huddled and overlapping with neighbouring stars at ever greater distances between us and their host galaxies, requiring careful accounting for this effect. Intervening dust further complicates the certainty of the measurements in visible light. Webb slices through the dust and naturally isolates the Cepheids from neighbouring stars because its vision is sharper than Hubble’s at infrared wavelengths.

“Combining Webb and Hubble gives us the best of both worlds. We find that the Hubble measurements remain reliable as we climb farther along the cosmic distance ladder,” said Riess.

A face-on spiral galaxy with four spiral arms that curve outward in a counterclockwise direction. The spiral arms are filled with young, blue stars and peppered with purplish star-forming regions that appear as small blobs. The middle of the galaxy is much brighter and more yellowish, and has a distinct narrow linear bar angled from 11 o’clock to 5 o’clock. Dozens of red background galaxies are scattered across the image. The background of space is black.
This image of NGC 5468, a galaxy located about 130 million light-years from Earth, combines data from the Hubble and James Webb space telescopes. This is the most distant galaxy in which Hubble has identified Cepheid variable stars. These are important milepost markers for measuring the expansion rate of the Universe. The distance calculated from Cepheids has been cross-correlated with a Type Ia supernova in the galaxy. Type Ia supernovae are so bright they are used to measure cosmic distances far beyond the range of the Cepheids, extending measurements of the Universe’s expansion rate deeper into space.
Credit: NASA, ESA, CSA, STScI, A. Riess (JHU/STScI)

The new Webb observations include five host galaxies of eight Type Ia supernovae containing a total of 1000 Cepheids, and reach out to the farthest galaxy where Cepheids have been well measured — NGC 5468, at a distance of 130 million light-years. 

“This spans the full range where we made measurements with Hubble. So, we’ve gone to the end of the second rung of the cosmic distance ladder,”

said co-author Gagandeep Anand of the Space Telescope Science Institute in Baltimore, which operates the Webb and Hubble Telescopes for NASA.

Together, Hubble’s and Webb’s confirmation of the Hubble Tension sets up other observatories to possibly settle the mystery, including NASA’s upcoming Nancy Grace Roman Space Telescope and ESA’s recently launched Euclid mission.

At present it’s as though the distance ladder observed by Hubble and Webb has firmly set an anchor point on one shoreline of a river, and the afterglow of the Big Bang observed by Planck from the beginning of the Universe is set firmly on the other side. How the Universe’s expansion was changing in the billions of years between these two endpoints has yet to be directly observed.

“We need to find out if we are missing something on how to connect the beginning of the Universe and the present day,” said Riess.

These findings were published in the 6 February 2024 issue of The Astrophysical Journal Letters.

 

Press release from ESA Webb.

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