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Webb images young, giant exoplanets in HR 8799, detects carbon dioxide

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This image shows the planetary system HR 8799. The image background is black. At the centre of the image, there is a symbol representing a star labeled HR 8799. This star blocks the light from the host star. There are four exoplanets, which look like fuzzy dots, pictured in the image surrounding the star. Furthest from the star is a fuzzy, faint blue dot, labeled b, at the 10 o’clock position. At the one o’clock position, second furthest from the star is a blueish-white fuzzy dot labeled c. Just below that is an orange dot labeled e. At the four o’clock position, still nearby the star, is another fuzzy white dot labeled d.

Webb images young, giant exoplanets in HR 8799, detects carbon dioxide

Findings suggest giant exoplanets in HR 8799 system likely formed like Jupiter and Saturn.

The NASA/ESA/CSA James Webb Space Telescope has captured direct images of multiple gas giant planets within an iconic planetary system. HR 8799, a young system 130 light-years away, has long been a key target for planet formation studies.

This image shows the planetary system HR 8799. The image background is black. At the centre of the image, there is a symbol representing a star labeled HR 8799. This star blocks the light from the host star. There are four exoplanets, which look like fuzzy dots, pictured in the image surrounding the star. Furthest from the star is a fuzzy, faint blue dot, labeled b, at the 10 o’clock position. At the one o’clock position, second furthest from the star is a blueish-white fuzzy dot labeled c. Just below that is an orange dot labeled e. At the four o’clock position, still nearby the star, is another fuzzy white dot labeled d.
The NASA/ESA/CSA James Webb Space Telescope has provided the clearest look yet at the iconic multi-planet system HR 8799. The observations detected carbon dioxide in each of the planets, which provides strong evidence that the system’s four giant planets formed much like Jupiter and Saturn, by slowly building solid cores that attract gas from within a protoplanetary disk. Colours are applied to filters from Webb’s NIRCam (Near-Infrared Camera), revealing their intrinsic differences. A star symbol marks the location of the host star HR 8799, whose light has been blocked by a coronagraph. The colours in this image, which represent different wavelengths captured by Webb’s NIRCam, tell researchers about the temperatures and composition of the planets. HR 8799 b, which orbits around 10.1 billion kilometres from the star, is the coldest of the bunch, and the richest in carbon dioxide. HR 8799 e orbits 2.4 billion kilometres from its star, and likely formed closer to the host star, where there were stronger variations in the composition of material. In this image, the colour blue is assigned to 4.1 micron light, green to 4.3 micron light, and red to the 4.6 micron light. Credit: NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI)

The observations indicate that the well-studied planets of HR 8799 are rich in carbon dioxide gas. This provides strong evidence that the system’s four giant planets formed much like Jupiter and Saturn, by slowly building solid cores that attract gas from within a protoplanetary disk.

The results also confirm that Webb can infer the chemistry of exoplanet atmospheres through imaging. This technique complements Webb’s powerful spectroscopic instruments, which resolve the atmospheric composition.

“By spotting these strong carbon dioxide features, we have shown there is a sizable fraction of heavier elements, like carbon, oxygen, and iron, in these planets’ atmospheres,” said William Balmer, of Johns Hopkins University in Baltimore. “Given what we know about the star they orbit, that likely indicates they formed via core accretion, which is an exciting conclusion for planets that we can directly see.”

Graphic titled “Exoplanet HR 8799 e: Carbon Dioxide in Gas Giant Exoplanet” has three data points with error bars and a best-fit model for low metal content and high metal content on a graph of Amount of Light from the Planet on the y-axis versus Wavelength of Light in microns on x-axis. Y-axis ranges from less light at bottom to more light at top. X-axis ranges from 3.6 to 5.0 microns. Webb NIRCam data consists of 3 points, plotted in red, with white error bars above and below each point. The best-fit models are jagged blue and yellow lines with several broad peaks and valleys. Two features are labeled with vertical columns. From 4.3 microns to nearly 4.4 microns, a green column is labeled Carbon Dioxide CO2. From nearly 4.4 microns to nearly 4.8 microns, a red column is labeled Carbon Monoxoide CO2.
This graph shows a spectrum of one of the planets in the HR 8799 system, HR 8799 e, which displays the amounts of near-infrared light detected from the planet by Webb at different wavelengths.
The blue and yellow lines are a best-fit model for an atmosphere that would be either low or high in metals heavier than helium, including carbon, also known as metallicity. The Webb data is consistent with a high metallicity planet. Spectral fingerprints of carbon dioxide and carbon monoxide appear in data collected by Webb’s NIRCam (Near-Infrared Camera). Credit: NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI)

Balmer is the lead author of the study announcing the results published today in The Astrophysical Journal. Balmer and his team’s analysis also includes Webb’s observation of a system 97 light-years away called 51 Eridani.

HR 8799 is a young system about 30 million years old, a fraction of our solar system’s 4.6 billion years. Still hot from their tumultuous formation, the planets within HR 8799 emit large amounts of infrared light that give scientists valuable data on how they formed.

Giant planets can take shape in two ways: by slowly building solid cores with heavier elements that attract gas, just like the giants in our solar system, or when particles of gas rapidly coalesce into massive objects from a young star’s cooling disk, which is made mostly of the same kind of material as the star. Knowing which formation model is more common can give scientists clues to distinguish between the types of planets they find in other systems.

“Our hope with this kind of research is to understand our own solar system, life, and ourselves in comparison to other exoplanetary systems, so we can contextualize our existence,” Balmer said. “We want to take pictures of other solar systems and see how they’re similar or different when compared to ours. From there, we can try to get a sense of how weird our solar system really is—or how normal.”

Of the nearly 6,000 exoplanets discovered, few have been directly imaged, as even giant planets are many thousands of times fainter than their stars. The images of HR 8799 and 51 Eridani were made possible by Webb’s NIRCam (Near-Infrared Camera) coronagraph, which blocks light from bright stars to reveal otherwise hidden worlds.

This image shows the exoplanet 51 Eri b. The image is mostly black, with very faint residual red dots apparent in the central region of the image. At the centre of the image, there is a symbol representing a star labeled 51 Eri. This star blocks the light from the host star. To the left of the circle is a fuzzy bright red circle, which is the exoplanet, labeled b.
The NASA/ESA/CSA James Webb Space Telescope’s NIRCam (Near-Infrared Camera) captured this image of Eridani 51 b, a cool, young exoplanet that orbits 17.7 billion kilometres from its star. Its distance is equivalent to a location between the orbits of Neptune and Saturn in our solar system. The observations detected the planet is rich in carbon dioxide, providing strong evidence that the planet formed much like Jupiter and Saturn, by slowly building a solid core that attracted gas from within a protoplanetary disk.
The 51 Eridani system is 96 light-years from Earth. This image includes filters representing 4.1-micron light as red. Credit: NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI)

This technology allowed the team to look for infrared light emitted by the planets in wavelengths that are absorbed by specific gases. The team found that the four HR 8799 planets contain more heavy elements than previously thought.

“Webb’s unique capabilities are allowing us to explore the wide diversity of these directly-imaged planets for the first time. This gives us important clues as to how such planetary systems have formed.” said Emily Rickman of the European Space Agency, a co-author of the study. “These new observations reiterate how valuable the HR 8799 multi-planet system is as a stepping stone to understand the formation of exoplanetary systems and of our own Solar System.”

The team is paving the way for more detailed observations to determine whether objects they see orbiting other stars are truly giant planets or objects such as brown dwarfs, which form like stars but don’t accumulate enough mass to ignite nuclear fusion.

“We have other lines of evidence that hint at these four HR 8799 planets forming using this bottom-up approach,” said Laurent Pueyo, an astronomer at the Space Telescope Science Institute in Baltimore, who co-led the work. “How common is this for planets we can directly image? We don’t know yet, but we’re proposing more Webb observations to answer that question.”

“We knew Webb could measure colours of the outer planets in directly imaged systems,” added Rémi Soummer, director of STScI’s Russell B. Makidon Optics Lab and former lead for Webb coronagraph operations. “We have been waiting for 10 years to confirm that our finely tuned operations of the telescope would also allow us to access the inner planets. Now the results are in and we can do interesting science with it.”

The NIRCam observations of HR 8799 and 51 Eridani were conducted as part of Guaranteed Time Observations programmes 1194 and 1412 respectively.

Press release from ESA Webb.

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Webb finds candidates for first young brown dwarfs outside the Milky Way, in the star cluster NGC 602

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young brown dwarfs outside the Milky Way NGC 602 A star cluster is shown inside a large nebula of many-coloured gas and dust. The material forms dark ridges and peaks of gas and dust surrounding the cluster, lit on the inner side, while layers of diffuse, translucent clouds blanket over them. Around and within the gas, a huge number of distant galaxies can be seen, some quite large, as well as a few stars nearer to us which are very large and bright.

Webb finds candidates for first young brown dwarfs outside the Milky Way, in the star cluster NGC 602

An international team of astronomers has used the NASA/ESA/CSA James Webb Space Telescope to detect the first rich population of brown dwarf candidates outside the Milky Way in the star cluster NGC 602.

Near the outskirts of the Small Magellanic Cloud, a satellite galaxy roughly 200 000 light-years from Earth, lies the young star cluster NGC 602. The local environment of this cluster is a close analogue of what existed in the early Universe, with very low abundances of elements heavier than hydrogen and helium. The existence of dark clouds of dense dust and the fact that the cluster is rich in ionised gas also suggest the presence of ongoing star formation processes. Together with its associated HII [1] region N90, which contains clouds of ionised atomic hydrogen, this cluster provides a valuable opportunity to examine star formation scenarios under dramatically different conditions from those in the solar neighbourhood.

An international team of astronomers, including Peter Zeidler, Elena Sabbi, Elena Manjavacas and Antonella Nota, used Webb to observe NGC 602 and they detected candidates for the first young brown dwarfs outside our Milky Way.

“Only with the incredible sensitivity and spatial resolution in the correct wavelength regime is it possible to detect these objects at such great distances,” shared lead author Peter Zeidler of AURA/STScI for the European Space Agency. “This has never been possible before and also will remain impossible from the ground for the foreseeable future.”

Brown dwarfs are the more massive cousins of giant gas planets (typically ranging from roughly 13 to 75 Jupiter masses, and sometimes lower). They are free-floating, meaning that they are not gravitationally bound to a star as exoplanets are. However, some of them share characteristics with exoplanets, like their atmospheric composition and storm patterns.

“Until now, we’ve known of about 3000 brown dwarfs, but they all live inside our own galaxy,” added team member Elena Manjavacas of AURA/STScI for the European Space Agency.

“This discovery highlights the power of using both Hubble and Webb to study young stellar clusters,” explained team member Antonella Nota, executive director of the International Space Science Institute in Switzerland and the previous Webb Project Scientist for ESA. “Hubble showed that NGC602 harbors very young low mass stars, but only with Webb we can finally see the extent and the significance of the substellar mass formation in this cluster. Hubble and Webb are an amazingly powerful telescope duo!”

“Our results fit very well with the theory that the mass distribution of bodies below the hydrogen burning limit is simply a continuation of the stellar distribution,” shared Zeidler. “It seems they form in the same way, they just don’t accrete enough mass to become a fully fledged star.”

The team’s data include a new image from Webb’s Near-InfraRed Camera (NIRCam) of NGC 602, which highlights the cluster stars, the young stellar objects, and the surrounding gas and dust ridges, as well as the gas and dust itself, while also showing the significant contamination by background galaxies and other stars in the Small Magellanic Cloud. These observations were made in April 2023.

“By studying the young metal-poor brown dwarfs newly discovered in NGC602, we are getting closer to unlocking the secrets of how stars and planets formed in the harsh conditions of the early Universe,“ added team member Elena Sabbi of NSF’s NOIRLab, the University of Arizona, and the Space Telescope Science Institute.

“These are the first substellar objects outside the Milky Way” added Manjavacas. “We need to be ready for new ground-breaking discoveries in these new objects!”

These observations were made as part of the JWST GO programme #2662 (PI: P. Zeidler). The results have been published in The Astrophysical Journal.

A star cluster is shown inside a large nebula of many-coloured gas and dust. The material forms dark ridges and peaks of gas and dust surrounding the cluster, lit on the inner side, while layers of diffuse, translucent clouds blanket over them. Around and within the gas, a huge number of distant galaxies can be seen, some quite large, as well as a few stars nearer to us which are very large and bright.
Near the outskirts of the Small Magellanic Cloud, a satellite galaxy roughly 200 000 light-years from Earth, lies the young star cluster NGC 602, which is featured in this new image from the NASA/ESA/CSA James Webb Space Telescope. This image includes data from Webb’s NIRCam (Near-InfraRed Camera) and MIRI (Mid-InfraRed Instrument).
The local environment of this cluster is a close analogue of what existed in the early Universe, with very low abundances of elements heavier than hydrogen and helium. The existence of dark clouds of dense dust and the fact that the cluster is rich in ionised gas also suggest the presence of ongoing star formation processes. This cluster provides a valuable opportunity to examine star formation scenarios under dramatically different conditions from those in the solar neighbourhood.
An international team of astronomers, including Peter Zeidler, Elena Sabbi, and Antonella Nota, used Webb to observe NGC 602 and detected candidates for the first young brown dwarfs outside our Milky Way.
Credit: ESA/Webb, NASA & CSA, P. Zeidler, E. Sabbi, A. Nota, M. Zamani (ESA/Webb)

Notes

[1] Some of the most beautiful extended objects that we can see are known as HII regions, also called diffuse or emission nebulae. They contain mostly ionised hydrogen and are found throughout the interstellar medium in the Milky Way and in other galaxies.

Press release from ESA Webb.

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Webb captures star clusters in Cosmic Gems arc

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This image shows a portion of the lensing galaxy cluster SPT-CL J0615−5746. Two distinct lensed galaxies are visible, of which the lower galaxy (known as the Cosmic Gems arc) is shown with several galaxy clusters within.

Webb captures star clusters in Cosmic Gems arc

An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to discover gravitationally bound star clusters when the Universe was 460 million years old. This is the first discovery of star clusters in an infant galaxy less than 500 million years after the Big bang.

This image shows two panels. On the right is field of many galaxies on the black background of space, known as the galaxy cluster SPT-CL J0615−5746. On the left is a callout image from a portion of this galaxy cluster showing two distinct lensed galaxies. The Cosmic Gems arc is shown with several galaxy clusters.
An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to discover gravitationally bound star clusters when the Universe was 460 million years old. This is the first discovery of star clusters in an infant galaxy less than 500 million years after the Big bang.
Young galaxies in the early Universe underwent significant burst phases of star formation, generating substantial amounts of ionising radiation. However, because of their cosmological distances, direct studies of their stellar content have proven challenging. Using Webb, an international team of astronomers have now detected five young massive star clusters in the Cosmic Gems arc (SPT0615-JD1), a strongly-lensed galaxy emitting light when the Universe was roughly 460 million years old, looking back across 97% of cosmic time.
The Cosmic Gems arc was initially discovered in NASA/ESA Hubble Space Telescope images obtained by the RELICS (Reionization Lensing Cluster Survey) programme of the lensing galaxy cluster SPT-CL J0615−5746.
With Webb, the science team can now see where stars formed and how they are distributed, in a similar way to how the Hubble Space Telescope is used to study local galaxies. Webb’s view provides a unique opportunity to study star formation and the inner workings of infant galaxies at such an unprecedented distance.
Credit: ESA/Webb, NASA & CSA, L. Bradley (STScI), A. Adamo (Stockholm University) and the Cosmic Spring collaboration

Young galaxies in the early Universe underwent significant burst phases of star formation, generating substantial amounts of ionising radiation. However, because of their cosmological distances, direct studies of their stellar content have proven challenging. Using Webb, an international team of astronomers have now detected five young massive star clusters in the Cosmic Gems arc (SPT0615-JD1), a strongly-lensed galaxy emitting light when the Universe was roughly 460 million years old, looking back across 97% of cosmic time.

The Cosmic Gems arc was initially discovered in NASA/ESA Hubble Space Telescope images obtained by the RELICS (Reionization Lensing Cluster Survey) programme of the lensing galaxy cluster SPT-CL J0615−5746.

“These galaxies are thought to be a prime source of the intense radiation that reionised the early Universe,” shared lead author Angela Adamo of Stockholm University and the Oskar Klein Centre in Sweden. “What is special about the Cosmic Gems arc is that thanks to gravitational lensing we can actually resolve the galaxy down to parsec scales!”

A field of galaxies on the black background of space. In the middle is a collection of dozens of yellowish galaxies that form a foreground galaxy cluster. Among them are distorted linear features, which mostly appear to follow invisible concentric circles curving around the centre of the image. The linear features are created when the light of a background galaxy is bent and magnified through gravitational lensing. A variety of brightly coloured, red and blue galaxies of various shapes are scattered across the image, making it feel densely populated.
An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to discover gravitationally bound star clusters when the Universe was 460 million years old. This is the first discovery of star clusters in an infant galaxy less than 500 million years after the Big bang.
Young galaxies in the early Universe underwent significant burst phases of star formation, generating substantial amounts of ionising radiation. However, because of their cosmological distances, direct studies of their stellar content have proven challenging. Using Webb, an international team of astronomers have now detected five young massive star clusters in the Cosmic Gems arc (SPT0615-JD1), a strongly-lensed galaxy emitting light when the Universe was roughly 460 million years old, looking back across 97% of cosmic time.
The Cosmic Gems arc was initially discovered in NASA/ESA Hubble Space Telescope images obtained by the RELICS (Reionization Lensing Cluster Survey) programme of the lensing galaxy cluster SPT-CL J0615−5746.
With Webb, the science team can now see where stars formed and how they are distributed, in a similar way to how the Hubble Space Telescope is used to study local galaxies. Webb’s view provides a unique opportunity to study star formation and the inner workings of infant galaxies at such an unprecedented distance.
Credit: ESA/Webb, NASA & CSA, L. Bradley (STScI), A. Adamo (Stockholm University) and the Cosmic Spring collaboration

With Webb, the science team can now see where stars formed and how they are distributed, in a similar way to how the Hubble Space Telescope is used to study local galaxies. Webb’s view provides a unique opportunity to study star formation and the inner workings of infant galaxies at such an unprecedented distance.

“Webb’s incredible sensitivity and angular resolution at near-infrared wavelengths, combined with gravitational lensing provided by the massive foreground galaxy cluster, enabled this discovery,” explained Larry Bradley of the Space Telescope Science Institute and PI of the Webb observing programme that captured these data.”No other telescope could have made this discovery.”

“The surprise and astonishment was incredible when we opened the Webb images for the first time,” added Adamo. “We saw a little chain of bright dots, mirrored from one side to the other — these cosmic gems are star clusters! Without Webb we would not have known we were looking at star clusters in such a young galaxy!” 

In our Milky Way we see ancient globular clusters of stars, which are bound by gravity and have survived for billions of years. These are old relics of intense star formation in the early Universe, but it is not well understood where and when these clusters formed. The detection of massive young star clusters in the Cosmic Gems arc provides us with an excellent view of the early stages of a process that may go on to form globular clusters. The newly detected clusters in the arc are massive, dense and located in a very small region of their galaxy, but they also contribute the majority of the ultraviolet light coming from their host galaxy. The clusters are significantly denser than nearby star clusters. This discovery will help scientists to better understand how infant galaxies formed their stars and where globular clusters formed.

This image shows a portion of the lensing galaxy cluster SPT-CL J0615−5746. Two distinct lensed galaxies are visible, of which the lower galaxy (known as the Cosmic Gems arc) is shown with several galaxy clusters within.
An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to discover gravitationally bound star clusters when the Universe was 460 million years old. This is the first discovery of star clusters in an infant galaxy less than 500 million years after the Big bang.
Young galaxies in the early Universe underwent significant burst phases of star formation, generating substantial amounts of ionising radiation. However, because of their cosmological distances, direct studies of their stellar content have proven challenging. Using Webb, an international team of astronomers have now detected five young massive star clusters in the Cosmic Gems arc (SPT0615-JD1), a strongly-lensed galaxy emitting light when the Universe was roughly 460 million years old, looking back across 97% of cosmic time.
The Cosmic Gems arc was initially discovered in NASA/ESA Hubble Space Telescope images obtained by the RELICS (Reionization Lensing Cluster Survey) programme of the lensing galaxy cluster SPT-CL J0615−5746.
With Webb, the science team can now see where stars formed and how they are distributed, in a similar way to how the Hubble Space Telescope is used to study local galaxies. Webb’s view provides a unique opportunity to study star formation and the inner workings of infant galaxies at such an unprecedented distance.
Credit: ESA/Webb, NASA & CSA, L. Bradley (STScI), A. Adamo (Stockholm University) and the Cosmic Spring collaboration

The team notes that this discovery connects a variety of scientific fields.

“These results provide direct evidence that indicates proto-globular clusters formed in faint galaxies during the reionisation era, which contributes to our understanding of how these galaxies have succeeded in reionising the Universe,” explained Adamo. “This discovery also places important constraints on the formation of globular clusters and their initial properties. For instance, the high stellar densities found in the clusters provide us with the first indication of the processes taking place in their interiors, giving new insights into the possible formation of very massive stars and black hole seeds, which are both important for galaxy evolution.”

In the future, the team hopes to build a sample of galaxies for which similar resolutions can be achieved.

“I am confident there are other systems like this waiting to be uncovered in the early Universe, enabling us to further our understanding of early galaxies,”

said Eros Vanzella from the INAF – Astrophysics and Space Science Observatory of Bologna (OAS), Italy, one of the main contributors to the work.

A field of galaxies on the black background of space. In the middle is a collection of dozens of yellowish galaxies that form a foreground galaxy cluster. Among them are distorted linear features, which mostly appear to follow invisible concentric circles curving around the centre of the image. The linear features are created when the light of a background galaxy is bent and magnified through gravitational lensing. A variety of brightly coloured, red and blue galaxies of various shapes are scattered across the image, making it feel densely populated.
An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to discover gravitationally bound star clusters when the Universe was 460 million years old. This is the first discovery of star clusters in an infant galaxy less than 500 million years after the Big bang.
Young galaxies in the early Universe underwent significant burst phases of star formation, generating substantial amounts of ionising radiation. However, because of their cosmological distances, direct studies of their stellar content have proven challenging. Using Webb, an international team of astronomers have now detected five young massive star clusters in the Cosmic Gems arc (SPT0615-JD1), a strongly-lensed galaxy emitting light when the Universe was roughly 460 million years old, looking back across 97% of cosmic time.
The Cosmic Gems arc was initially discovered in NASA/ESA Hubble Space Telescope images obtained by the RELICS (Reionization Lensing Cluster Survey) programme of the lensing galaxy cluster SPT-CL J0615−5746.
With Webb, the science team can now see where stars formed and how they are distributed, in a similar way to how the Hubble Space Telescope is used to study local galaxies. Webb’s view provides a unique opportunity to study star formation and the inner workings of infant galaxies at such an unprecedented distance.
Credit: ESA/Webb, NASA & CSA, L. Bradley (STScI), A. Adamo (Stockholm University) and the Cosmic Spring collaboration

In the meantime, the team is preparing for further observations and spectroscopy with Webb.

“We plan to study this galaxy with Webb’s NIRSpec and MIRI instruments in Cycle 3,” added Bradley. “The NIRSpec observations will allow us to confirm the redshift of the galaxy and to study the ultraviolet emission of the star clusters, which will be used to study their physical properties in more detail. The MIRI observations will allow us to study the properties of ionised gas. The spectroscopic observations will also allow us to spatially map the star formation rate.”

These results have been published today in Nature. The data for this result were captured under Webb observing programme #4212 (PI: L. Bradley).

This image shows two panels. On the right is a field of many galaxies on the black background of space, known as the galaxy cluster SPT-CL J0615−5746. On the left is a callout image from a portion of this galaxy cluster showing two distinct lensed galaxies. The Cosmic Gems arc is shown with several galaxy clusters.
An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to discover gravitationally bound star clusters when the Universe was 460 million years old. This is the first discovery of star clusters in an infant galaxy less than 500 million years after the Big bang.
Young galaxies in the early Universe underwent significant burst phases of star formation, generating substantial amounts of ionising radiation. However, because of their cosmological distances, direct studies of their stellar content have proven challenging. Using Webb, an international team of astronomers have now detected five young massive star clusters in the Cosmic Gems arc (SPT0615-JD1), a strongly-lensed galaxy emitting light when the Universe was roughly 460 million years old, looking back across 97% of cosmic time.
The Cosmic Gems arc was initially discovered in NASA/ESA Hubble Space Telescope images obtained by the RELICS (Reionization Lensing Cluster Survey) programme of the lensing galaxy cluster SPT-CL J0615−5746.
With Webb, the science team can now see where stars formed and how they are distributed, in a similar way to how the Hubble Space Telescope is used to study local galaxies. Webb’s view provides a unique opportunity to study star formation and the inner workings of infant galaxies at such an unprecedented distance.
Credit: ESA/Webb, NASA & CSA, L. Bradley (STScI), A. Adamo (Stockholm University) and the Cosmic Spring collaboration

Bibliographic information:

Angela Adamo, Larry D. Bradley, Eros Vanzella, Adélaïde Claeyssens, Brian Welch4, Jose M Diego, Guillaume Mahler, Masamune Oguri, Keren Sharon, Abdurro’uf, Tiger Yu-Yang Hsiao, Xinfeng Xu, Matteo Messa, Augusto E. Lassen, Erik Zackrisson, Gabriel Brammer, Dan Coe, Vasily Kokorev, Massimo Ricotti, Adi Zitrin, Seiji Fujimoto, Akio K. Inoue, Tom Resseguier, Jane R. Rigby, Yolanda Jiménez-Teja, Rogier A. Windhorst, Takuya Hashimoto and Yoichi Tamura, Bound star clusters observed in a lensed galaxy 460 Myr after the Big Bang, Nature.

 

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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Webb discovers dusty cat’s tail in Beta Pictoris System

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A wide, thin horizontal orange line appears at the centre, extending almost to the edges, a debris disc seen edge-on. A thin blue-green disc is inclined about five degrees counterclockwise relative to the main orange disc. Cloudy, translucent grey material is most prominent near the orange main debris disc. Some of the grey material forms a curved feature in the upper right, resembling a cat’s tail. At the centre is a black circle with a bar. The central star, represented as a small white star icon, is blocked by an instrument known as a coronagraph. The background of space is black.

Webb discovers dusty cat’s tail in Beta Pictoris System

Beta Pictoris, a young planetary system located just 63 light-years away, continues to intrigue scientists even after decades of in-depth study. It possesses the first dust disc imaged around another star — a disc of debris produced by collisions between asteroids, comets, and planetesimals. Observations from the NASA/ESA Hubble Space Telescope revealed a second debris disc in this system [1], inclined with respect to the first. Now, a team of astronomers using the NASA/ESA/CSA James Webb Space Telescope to image the Beta Pictoris (Beta Pic) system has discovered a new, previously unseen structure.

A wide, thin horizontal orange line appears at the centre, extending almost to the edges, a debris disc seen edge-on. A thin blue-green disc is inclined about five degrees counterclockwise relative to the main orange disc. Cloudy, translucent grey material is most prominent near the orange main debris disc. Some of the grey material forms a curved feature in the upper right, resembling a cat’s tail. At the centre is a black circle with a bar. The central star, represented as a small white star icon, is blocked by an instrument known as a coronagraph. The background of space is black.
This image from Webb’s MIRI (Mid-Infrared Instrument) shows the star system Beta Pictoris. An edge-on disc of dusty debris generated by collisions between planetesimals (orange) dominates the view. A hotter, secondary disc (cyan) is inclined by about 5 degrees relative to the primary disc. The curved feature at upper right, which the science team nicknamed the “cat’s tail,” has never been seen before. A coronagraph (black circle and bar) has been used to block the light of the central star, whose location is marked with a white star shape. In this image light at 15.5 microns is coloured cyan and 23 microns is orange (filters F1550C and F2300C, respectively).
Credit: NASA, ESA, CSA, STScI, C. Stark and K. Lawson (NASA GSFC), J. Kammerer (ESO), and M. Perrin (STScI)

The team, led by Isabel Rebollido of the Astrobiology Center in Spain, and now an ESA Research Fellow, used Webb’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) to investigate the composition of Beta Pic’s previously detected main and secondary debris discs. The results exceeded their expectations, revealing a sharply inclined branch of dust, shaped like a cat’s tail, that extends from the southwest portion of the secondary debris disc.

“Beta Pictoris is the debris disc that has it all: It has a really bright, close star that we can study very well,” said Rebollido. “While there have been previous observations from the ground in this wavelength range, they did not have the sensitivity and the spatial resolution that we now have with Webb, so they didn’t detect this feature.”

A wide, thin horizontal orange line appears at the centre, extending almost to the edges, a debris disc seen edge-on. A thin blue-green disc is inclined about five degrees counterclockwise relative to the main orange disc. Cloudy, translucent grey material is most prominent near the orange main debris disc. Some of the grey material forms a curved feature in the upper right, resembling a cat’s tail. At the centre is a black circle with a bar. The central star, represented as a small white star icon, is blocked by an instrument known as a coronagraph. The background of space is black.
This image from Webb’s MIRI (Mid-Infrared Instrument) shows the star system Beta Pictoris. An edge-on disc of dusty debris generated by collisions between planetesimals (orange) dominates the view. A hotter, secondary disc (cyan) is inclined by about 5 degrees relative to the primary disc. The curved feature at upper right, which the science team nicknamed the “cat’s tail,” has never been seen before. A coronagraph (black circle and bar) has been used to block the light of the central star, whose location is marked with a white star shape. In this image light at 15.5 microns is coloured cyan and 23 microns is orange (filters F1550C and F2300C, respectively).
Credit:
NASA, ESA, CSA, STScI, C. Stark and K. Lawson (NASA GSFC), J. Kammerer (ESO), and M. Perrin (STScI)

A Star’s Portrait Improved with Webb

Even with Webb, peering at Beta Pic in the right wavelength range — in this case, the mid-infrared — was crucial to detect the cat’s tail, as it only appeared in the MIRI data. Webb’s mid-infrared data also revealed differences in temperature between Beta Pic’s two discs, which likely is due to differences in composition.

“We didn’t expect Webb to reveal that there are two different types of material around Beta Pic, but MIRI clearly showed us that the material of the secondary disc and cat’s tail is hotter than the main disc,” said Christopher Stark, a co-author of the study at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The dust that forms that disc and tail must be very dark, so we don’t easily see it at visible or near-infrared wavelengths — but in the mid-infrared, it’s glowing.”

To explain the hotter temperature, the team deduced that the dust may be highly porous “organic refractory material,” similar to the matter found on the surfaces of comets and asteroids in our solar system. For example, a preliminary analysis of material sampled from asteroid Bennu by NASA’s OSIRIS-Rex mission found it to be very dark and carbon-rich, much like what MIRI detected at Beta Pic.

The Tail’s Puzzling Beginning Warrants Future Research

However, a major lingering question remains: What could explain the shape of the cat’s tail, a uniquely curved feature unlike what is seen in discs around other stars?

Rebollido and the team modelled various scenarios in an attempt to emulate the cat’s tail and unravel its origins. Though further research and testing is required, the team presents a strong hypothesis that the cat’s tail is the result of a dust production event that occurred a mere one hundred years ago.

“Something happens — like a collision — and a lot of dust is produced,” shared Marshall Perrin, a co-author of the study at the Space Telescope Science Institute in Baltimore, Maryland. “At first, the dust goes in the same orbital direction as its source, but then it also starts to spread out. The light from the star pushes the smallest, fluffiest dust particles away from the star faster, while the bigger grains do not move as much, creating a long tendril of dust.”

“The cat’s tail feature is highly unusual, and reproducing the curvature with a dynamical model was difficult,” explained Stark. “Our model requires dust that can be pushed out of the system extremely rapidly, which again suggests it’s made of organic refractory material.”

The team’s preferred model explains the sharp angle of the tail away from the disc as a simple optical illusion. Our perspective combined with the curved shape of the tail creates the observed angle of the tail, while in fact, the arc of material is only departing from the disc at a five-degree incline. Taking into consideration the tail’s brightness, the team estimates the amount of dust within the cat’s tail to be equivalent to a large main belt asteroid spread out across 16 billion kilometres.

A recent dust production event within Beta Pic’s debris discs could also explain an asymmetry previously spotted by the Atacama Large Millimeter/submillimeter Array in 2014: a clump of carbon monoxide (CO) located near the cat’s tail. Since the star’s radiation should break down CO within roughly one hundred years, this still-present concentration of gas could be lingering evidence of the same event.

“Our research suggests that Beta Pic may be even more active and chaotic than we had previously thought,” said Stark. “Webb continues to surprise us, even when looking at the most well-studied objects. We have a completely new window into these planetary systems.”

These results were presented in a press conference at the 243rd meeting of the American Astronomical Society in New Orleans, Louisiana.

The observations were taken as part of Guaranteed Time Observation program 1411.

Notes

[1] Learn more about these 2006 Hubble observations that revealed a second debris disc in the Beta Pic system here.

A wide, thin horizontal orange line appears at the centre, extending almost to the edges, a debris disc seen edge-on. A thin blue-green disc is inclined about five degrees counterclockwise relative to the main orange disc. Cloudy, translucent grey material is most prominent near the orange main debris disc. Some of the grey material forms a curved feature in the upper right, resembling a cat’s tail. At the centre is a black circle with a bar. The central star, represented as a small white star icon, is blocked by an instrument known as a coronagraph. The background of space is black.
This image from Webb’s MIRI (Mid-Infrared Instrument) shows the star system Beta Pictoris. An edge-on disc of dusty debris generated by collisions between planetesimals (orange) dominates the view. A hotter, secondary disc (cyan) is inclined by about 5 degrees relative to the primary disc. The curved feature at upper right, which the science team nicknamed the “cat’s tail,” has never been seen before. A coronagraph (black circle and bar) has been used to block the light of the central star, whose location is marked with a white star shape. In this image light at 15.5 microns is coloured cyan and 23 microns is orange (filters F1550C and F2300C, respectively).
Credit: NASA, ESA, CSA, STScI, C. Stark and K. Lawson (NASA GSFC), J. Kammerer (ESO), and M. Perrin (STScI)

 

Press release from ESA Webb.

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Hubble hunts for intermediate-sized black hole close to home

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Hubble hunts for intermediate-sized black hole close to home; the study has been published in the Monthly Notices of the Royal Astronomical Society

Hubble hunts for intermediate-sized black hole close to home; the study has been published in the Monthly Notices of the Royal Astronomical Society

Astronomers using the NASA/ESA Hubble Space Telescope have come up with what they say is some of their best evidence yet for the presence of a rare class of intermediate-sized black holes, having found a strong candidate lurking at the heart of the closest globular star cluster to Earth, located 6000 light-years away.

Messier 4 M4
Hubble hunts for intermediate-sized black hole close to home. A Hubble Space Telescope image of the globular star cluster, Messier 4. The cluster is a dense collection of several hundred thousand stars. Astronomers suspect that an intermediate-mass black hole, weighing as much as 800 times the mass of our Sun, is lurking, unseen, at its core. Credit: ESA/Hubble & NASA

Like intense gravitational potholes in the fabric of space, virtually all black holes seem to come in two sizes: small and humongous. It’s estimated that our galaxy is littered with 100 million small black holes (several times the mass of our Sun) created from exploded stars. The universe at large is flooded with supermassive black holes, weighing millions or billions of times our Sun’s mass and found in the centres of galaxies.

A long-sought missing link is an intermediate-mass black hole, weighing roughly 100 to 100,000 times our Sun’s mass. How would they form, where would they hang out, and why do they seem to be so rare?

Astronomers have identified other possible intermediate-mass black holes using a variety of observational techniques. Two of the best candidates — 3XMM J215022.4-055108, which Hubble helped discover in 2020, and HLX-1, identified in 2009 — reside in the outskirts of other galaxies. Each of these possible black holes has the mass of tens of thousands of suns, and may have once been at the centres of dwarf galaxies.

Looking much closer to home, there have been a number of suspected intermediate-mass black holes detected in dense globular star clusters orbiting our Milky Way galaxy. For example, in 2008, Hubble astronomers announced the suspected presence of an intermediate-mass black hole in the globular cluster Omega Centauri. For a number of reasons, including the need for more data, these and other intermediate-mass black hole findings still remain inconclusive and do not rule out alternative theories.

Hubble’s unique capabilities have now been used to zero-in on the core of the globular star cluster Messier 4 (M4) to go black-hole hunting with higher precision than in previous searches.

“You can’t do this kind of science without Hubble,” 

said Eduardo Vitral of the Space Telescope Science Institute in Baltimore, Maryland, and formerly of the Institut d’Astrophysique de Paris (IAP, Sorbonne University) in Paris, France, lead author on a paper to be published in the Monthly Notices of the Royal Astronomical Society.

Vitral’s team has detected a possible intermediate-mass black hole of roughly 800 solar masses. The suspected object can’t be seen, but its mass is calculated by studying the motion of stars caught in its gravitational field, like bees swarming around a hive. Measuring their motion takes time, and a lot of precision. This is where Hubble accomplishes what no other present-day telescope can do. Astronomers looked at 12 years’ worth of M4 observations from Hubble, and resolved pinpoint stars.

ESA’s Gaia spacecraft also contributed to this result with scans of over 6000 stars that constrained the global shape of the cluster and its mass. Hubble’s data tend to rule out alternative theories for this object, such as a compact central cluster of unresolved stellar remnants like neutron stars, or smaller black holes swirling around each other.

“Using the latest Gaia and Hubble data, it was not possible to distinguish between a dark population of stellar remnants and a single larger point-like source,” says Vitral. “So one of the possible theories is that rather than being lots of separate small dark objects, this dark mass could be one medium-sized black hole.”

“We have good confidence that we have a very tiny region with a lot of concentrated mass. It’s about three times smaller than the densest dark mass that we had found before in other globular clusters,” he continued. “The region is more compact than what we can reproduce with numerical simulations when we take into account a collection of black holes, neutron stars, and white dwarfs segregated at the cluster’s centre. They are not able to form such a compact concentration of mass.”

A grouping of close-knit objects would be dynamically unstable. If the object isn’t a single intermediate-mass black hole, it would require an estimated 40 smaller black holes crammed into a space only one-tenth of a light-year across to produce the observed stellar motions. The consequences are that they would merge and/or be ejected in a game of interstellar pinball.

“We measure the motions of stars and their positions, and we apply physical models that try to reproduce these motions. We end up with a measurement of a dark mass extension in the cluster’s centre,” said Vitral. “The closer to the central mass, the more randomly the stars are moving. And, the greater the central mass, the faster these stellar velocities.”

Because intermediate-mass black holes in globular clusters have been so elusive, Vitral cautions, “While we cannot completely affirm that it is a central point of gravity, we can show that it is very small. It’s too tiny for us to be able to explain other than it being a single black hole. Alternatively, there might be a stellar mechanism we simply don’t know about, at least within current physics.”

“Science is rarely about discovering something new in a single moment. It’s about becoming more certain of a conclusion step by step, and this could be one step towards being sure that intermediate-mass black holes exist,” explains Gaia mission scientist Timo Prusti. “Data from Gaia Data Release 3 on the proper motion of stars in the Milky Way were essential in this study. Future Gaia Data Releases, as well as follow-up studies from the Hubble and James Webb Space Telescopes could shed further light.”

 

Press release from ESA Hubble

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Hubble Sees Summertime on Saturn

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Saturn summertime summer

Hubble Sees Summertime on Saturn

Saturn is truly the lord of the rings in this latest snapshot from NASA’s Hubble Space Telescope, taken on July 4, 2020, when the opulent giant world was 839 million miles from Earth. This new Saturn image was taken during summer in the planet’s northern hemisphere.

Saturn summertime Hubble summer
NASA’s Hubble Space Telescope captured this image of Saturn on July 4, 2020. Two of Saturn’s icy moons are clearly visible in this exposure: Mimas at right, and Enceladus at bottom. This image is taken as part of the Outer Planets Atmospheres Legacy (OPAL) project. OPAL is helping scientists understand the atmospheric dynamics and evolution of our solar system’s gas giant planets. In Saturn’s case, astronomers continue tracking shifting weather patterns and storms.
Credits: NASA, ESA, A. Simon (Goddard Space Flight Center), M.H. Wong (University of California, Berkeley), and the OPAL Team

 

Hubble found a number of small atmospheric storms. These are transient features that appear to come and go with each yearly Hubble observation. The banding in the northern hemisphere remains pronounced as seen in Hubble’s 2019 observations, with several bands slightly changing color from year to year. The ringed planet’s atmosphere is mostly hydrogen and helium with traces of ammonia, methane, water vapor, and hydrocarbons that give it a yellowish-brown color.

Hubble photographed a slight reddish haze over the northern hemisphere in this color composite. This may be due to heating from increased sunlight, which could either change the atmospheric circulation or perhaps remove ices from aerosols in the atmosphere. Another theory is that the increased sunlight in the summer months is changing the amounts of photochemical haze produced. “It’s amazing that even over a few years, we’re seeing seasonal changes on Saturn,” said lead investigator Amy Simon of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Conversely, the just-now-visible south pole has a blue hue, reflecting changes in Saturn’s winter hemisphere.

Hubble’s sharp view resolves the finely etched concentric ring structure. The rings are mostly made of pieces of ice, with sizes ranging from tiny grains to giant boulders. Just how and when the rings formed remains one of our solar system’s biggest mysteries. Conventional wisdom is that they are as old as the planet, over 4 billion years. But because the rings are so bright – like freshly fallen snow – a competing theory is that they may have formed during the age of the dinosaurs. Many astronomers agree that there is no satisfactory theory that explains how rings could have formed within just the past few hundred million years. “However, NASA’s Cassini spacecraft measurements of tiny grains raining into Saturn’s atmosphere suggest the rings can only last for 300 million more years, which is one of the arguments for a young age of the ring system,” said team member Michael Wong of the University of California, Berkeley.

Two of Saturn’s icy moons are clearly visible in this exposure: Mimas at right, and Enceladus at bottom.

This image is taken as part of the Outer Planets Atmospheres Legacy (OPAL) project. OPAL is helping scientists understand the atmospheric dynamics and evolution of our solar system’s gas giant planets. In Saturn’s case, astronomers continue tracking shifting weather patterns and storms.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

 

 

Press release from NASA, on Hubble capturing summertime data from Saturn.

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