In a new image from NASA’s James Webb Space Telescope, a galaxy named for its resemblance to a broad-brimmed Mexican hat appears more like an archery target.
20.11.2024
A distant planet seems to have a sulphur-rich atmosphere, hinting at alien volcanoes
Even JWST can’t separate these tiny planets from their host stars – as they orbit their stars too closely. But there is a way to “see” the planet’s atmosphere from this entangled light.
Today, we know of more than 5,000 exoplanets: planets outside our solar system that orbit other stars. While the effort to discover new worlds goes on, we’re steadily learning more about the exoplanets we’ve already detected: their sizes, what they’re made of and whether they have atmospheres.
Our team has now provided tentative evidence for a sulphur-rich atmosphere on a world that’s 1.5 times the size of Earth and located 35 light years away. If confirmed, it would be the smallest known exoplanet with an atmosphere. The potential presence of the gases sulphur dioxide (SO₂) and hydrogen sulphide (H₂S) in this atmosphere hint at a molten or volcanic surface.
In our solar system, we have two distinct categories of planets – the small rocky ones, including Earth and Mars, and the gas giants such as Jupiter and Saturn. However, exoplanets span a great spectrum of sizes. Our solar system lacks a planet whose size falls into the range between Earth and Neptune, but it turns out that’s the most common type of planet we have seen around other stars in our galaxy.
The ones closer to Neptune’s size are called sub-Neptunes and the ones closer to Earth’s size are called super-Earths. L 98-59 d is a super-Earth, slightly bigger and heavier than the Earth. The composition of the atmospheres of these planets is still an open question, one that we are only starting to explore with the James Webb Space Telescope (JWST), launched in 2021.
L 98-59 d was discovered in 2019 with Nasa’s Tess space telescope. Most exoplanets, including L 98-59 d, have been detected using the “transit method”. This measures the tiny dips in starlight when the planet passes in front of the star. This dip is more pronounced for larger planets and enables us to figure out the size of a planet.
Even JWST can’t separate these tiny planets from their host stars – as they orbit their stars too closely. But there is a way to “see” the planet’s atmosphere from this entangled light. When a planet passes in front of its star, some of the starlight filters through a planet’s atmosphere, hitting the gas molecules or atoms present there, on its way to us on Earth.
Every gas modifies the light in its own signature manner. From the light we receive from that star system, we can infer what the composition of that atmosphere might be. This is called transmission spectroscopy, a proven technique that has previously been used to confirm the presence of CO₂ in an exoplanet’s atmosphere.
I am part of an international team of scientists who used JWST to observe one transit of L 98-59 d across the disc of its host star. We then obtained the transmission spectrum of the atmosphere of the exoplanet from these observations. This spectrum hinted at the possible presence of an atmosphere filled with sulphur dioxide and hydrogen sulphide.
This discovery was surprising, as it stands out in stark contrast to the atmospheres of rocky planets in our own solar system, where water vapour and carbon dioxide are much more prevalent. Earth’s atmosphere, for example, is rich in nitrogen and oxygen, with trace amounts of water vapour. Meanwhile, Venus has a thick atmosphere dominated by carbon dioxide. Even Mars has a thin atmosphere dominated by carbon dioxide.
We then used computer models that incorporate our understanding of planetary atmospheres and the light coming from L 98-59 d to come up with a potential picture of the composition of this planet’s atmosphere. The absence of common gases such as carbon dioxide and the presence of SO₂ and H₂S suggests an atmosphere shaped by entirely different processes to those we’re familiar with in our solar system. This hints at unique and extreme conditions on L 98-59 d, such as a molten or volcanic surface.
Additional observations will be necessary to confirm the presence of these gases. JWST observations had previously spotted signs of SO₂ on an exoplanet, but this was a gas giant, not a potentially rocky world such as L 98-59 d.
Exo-volcanoes?
The potential presence of SO₂ and H₂S raises questions about their origin. One explosive possibility is volcanism driven by tidal heating, much like what is observed on Jupiter’s moon Io. The gravitational pull of the host star on this planet stretches and squeezes it as it goes along its orbit. This motion can heat up the centre of the planet, melting its interiors and producing extreme volcanic eruptions and possibly even oceans of magma.
Combined with its close proximity to the star (one year on this planet is seven and half Earth days), truly hellish temperatures can be reached on the surface. If future observations support the presence of such an atmosphere, not only would it be the smallest exoplanet to have a detected atmosphere, but also a crucial step towards understanding the nature of such planets.
Detecting atmospheres on small, rocky planets is exceptionally difficult, as the planets are very small compared to the host stars, and also as intense radiation from their host stars often strips the atmospheres away. These observations, while tantalizing, are only from a single transit. That means instrumental noise and other factors prevent us from making statistically strong claims. Future JWST observations will be key in confirming or refuting our analysis.
L 98-59 d may not be a candidate for life as we know it, but studying its sulphurous atmosphere and potential volcanism provides valuable insight into worlds around other stars. Extreme worlds like these help us understand the diversity of planetary evolution across the galaxy.
Quelle: SC
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Update: 27.11.2024
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Hats Off to NASA’s Webb: Sombrero Galaxy Dazzles in New Image
NASA’s James Webb Space Telescope recently imaged the Sombrero galaxy with its MIRI (Mid-Infrared Instrument), resolving the clumpy nature of the dust along the galaxy’s outer ring.
Credits: NASA, ESA, CSA, STScI
In Webb’s mid-infrared view of the Sombrero galaxy, also known as Messier 104 (M104), the signature, glowing core seen in visible-light images does not shine, and instead a smooth inner disk is revealed. The sharp resolution of Webb’s MIRI (Mid-Infrared Instrument) also brings into focus details of the galaxy’s outer ring, providing insights into how the dust, an essential building block for astronomical objects in the universe, is distributed. The galaxy’s outer ring, which appeared smooth like a blanket in imaging from NASA’s retired Spitzer Space Telescope, shows intricate clumps in the infrared for the first time.
Image B: Sombrero Galaxy (Hubble and Webb Image)
HUBBLE (VISIBLE) , HUBBLE’S VIEW OF THE SOMBRERO GALAXY. IN THIS VIEW, THE GALAXY IS AN OBLONG, PALE WHITE DISK WITH A GLOWING CORE OVER THE INNER DISK. THE OUTER DISK IS DARKER AND CLUMPY.
WEBB (MIRI) , WEBB’S VIEW OF THE SOMBRERO GALAXY. IN THIS VIEW, THE GALAXY IS A VERY OBLONG, BLUE DISK THAT EXTENDS FROM LEFT TO RIGHT AT AN ANGLE (FROM ABOUT 10 O’CLOCK TO 5 O’CLOCK). THE GALAXY HAS A SMALL BRIGHT CORE AT THE CENTER. THERE IS CLEAR INNER DISK THAT HAS SPECKLES OF STARS SCATTERED THROUGHOUT. THE OUTER DISK OF THE GALAXY IS WHITEISH-BLUE, AND CLUMPY, LIKE CLOUDS IN THE SKY.
BEFORE AND AFTER
Sombrero Galaxy (Hubble and Webb Image)
Nov 25, 2024
Researchers say the clumpy nature of the dust, where MIRI detects carbon-containing molecules called polycyclic aromatic hydrocarbons, can indicate the presence of young star-forming regions. However, unlike some galaxies studied with Webb, including Messier 82, where 10 times as many stars are born than the Milky Way galaxy, the Sombrero galaxy is not a particular hotbed of star formation. The rings of the Sombrero galaxy produce less than one solar mass of stars per year, in comparison to the Milky Way’s roughly two solar masses a year.
Even the supermassive black hole, also known as an active galactic nucleus, at the center of the Sombrero galaxy is rather docile, even at a hefty 9-billion-solar masses. It’s classified as a low luminosity active galactic nucleus, slowly snacking on infalling material from the galaxy, while sending off a bright, relatively small, jet.
Also within the Sombrero galaxy dwell some 2,000 globular clusters, collections of hundreds of thousands of old stars held together by gravity. This type of system serves as a pseudo laboratory for astronomers to study stars — thousands of stars within one system with the same age, but varying masses and other properties is an intriguing opportunity for comparison studies.
In the MIRI image, galaxies of varying shapes and colors litter the background of space. The different colors of these background galaxies can tell astronomers about their properties, including how far away they are.
The Sombrero galaxy is around 30 million light-years from Earth in the constellation Virgo.
A Bright Future Ahead
Stunning images like this, and an array of discoveries in the study of exoplanets, galaxies through time, star formation, and our own solar system, are still just the beginning. Recently, scientists from all over the world applied for observation time with Webb during its fourth year of science operations, which begins in July 2025.
General Observer time with Webb is more competitive than ever. A record-breaking 2,377 proposals were submitted by the Oct. 15, 2024, deadline, requesting about 78,000 hours of observation time. This is an oversubscription rate, the ratio defining the observation hours requested versus the actual time available in one year of Webb’s operations, of around 9 to 1.
The proposals cover a wide array of science topics, with distant galaxies being among the most requested observation time, followed by exoplanet atmospheres, stars and stellar populations, then exoplanet systems.
The Space Telescope Science Institute manages the proposal and program selection process for NASA. The submissions will now be evaluated by a Telescope Allocation Committee, a group of hundreds of members of the worldwide astronomical community, on a dual-anonymous basis, with selections announced in March 2025.
While time on Webb is limited, data from all of Webb’s programs is publicly archived, immediately after it’s taken, or after a time of exclusive access, in the Mikulski Archive for Space Telescopes (MAST) so it can be used by anyone in the world.
Quelle: NASA
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Update: 1.12.2024
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James Webb Space Telescope explores monster star supercluster Westerlund 1 (image)
"We pushed our detection limit down to the brown dwarfs of the cluster, which are the smallest stars that can form!"
A stunning image of the young stars of Westerlund 1 as seen by the JWST. (Image credit: NASA/ MIRI/ NIRCam/ Giuseppe, et al 2024/ EWOCS)
Using the James Webb Space Telescope, astronomers have taken a deep drive into a highly intriguing and massive young stellar cluster in the Milky Way. It's called Westerlund 1. Located around 12,000 light years from Earth, Westerlund 1 is also the closest supermassive star cluster to us.
Supermassive star clusters like Westerlund 1 are groupings of stars that contain masses equivalent to tens of thousands of suns. In these superclusters, the processes that favor star-forming environments and boost the births of stars and planets are extremely efficient.
At over 6.6 light-years wide, Westerlund 1 has a mass the same as around 63,000 suns. Hosting the largest and most compact population of monster stars in the Milky Way, with hundreds of very massive stars packed in a relatively small region, Westerlund 1 is a tantalizing target for astronomers aiming to better understand a range of stellar phenomena and the evolution of planetary systems.
"We pushed our detection limit down to the brown dwarfs of the cluster, which are the smallest stars that can form!" EWOCS team leader Mario Giuseppe of the Palermo Astronomical Observatory in Italy told Space.com. "Thus, we will be able to determine the true content of the cluster and to measure properties such as the mass distribution of its stars."
The James Webb Space Telescope (JWST) also offers detailed and deep observations taken in infrared wavelengths of light that can be used to highlight young stars still surrounded by planet-birthing protoplanetary disks.
"These may be forming planets right now," Giuseppe continued. "All this will allow us, for the first time, to determine the impact of the starburst environment on the products of star formation and the process of planet formation."
Westerlund 1 is one wonderland for astronomers
EWOCS not only works with observations from the JWST, but also with data from the Hubble Space Telescope, the Atacama Large Millimeter/submillimeter Array (ALMA), NASA's Chandra X-ray Space Telescope, and more, to study Westerlund 1 as well as the slightly more diminutive supercluster Westerlund 2.
"Westerlund 1 hosts the largest and most compact population of massive stars we know in the galaxy, with hundreds of very massive stars packed in a very small region, almost all of them being in close binary systems," Giuseppe said. "In such cases, the star-forming environment is dominated by energetic radiation [UV and X-rays] and high-speed, high-energy particles, which regulate star and planet formation."
A range of different conditions in galaxies can determine the rate at which stars form. As an example, epochs of intense star birth, known as "starburst periods," can be triggered when galaxies collide to cause an influx of gas and dust, which are the building blocks of new stars.
"In these cases, the typical star-forming environment takes the form of very massive and supermassive star-forming regions," Giuseppe said.
Such instances were more common in the early and turbulent universe when galactic collisions were more likely to occur. Formation rates have been quenched in the Milky Way because it's a "modern" galaxy, meaning starburst regions are few and far between.
"The Milky Way today hosts only a few supermassive clusters, with less than ten known," Giuseppe continued. "These few regions are crucially important because they allow us to study star- and planet-forming conditions which are typical of starburst galaxies in the early universe and to extend our knowledge of star and planet formation to the most extreme and energetic star-forming environments we know of."
Superclusters are often obscured by clouds of gas and dust between stars in the Milky Way and are usually buried in dense star fields. That means studying these sites of intense star formation, especially when investigating lower-mass stars in the region, requires a powerful telescope with a large light-gathering area that can capture infrared light, which, as briefly touched on, is capable of slipping through dense clouds of interstellar matter. Visible light cannot do that.
That's why the EWOCS team turned to the JWST and its main tools, the Mid-Infrared Instrument (MIRI) and the Near-Infrared Camera (NIRCam). Though Westerlund 1 has been studied by many other telescopes, including Hubble, the JWST still provided Giuseppe and colleagues with some unexpected results.
"The main surprises arrived from the MIRI images, that unveiled a dense and structured nebulosity [gas and dust] all around and within the cluster," the researcher said. "Such nebulosity can hardly be a remnant of the parental cloud from which the cluster formed about 5 million years ago."
This is because young clusters with a moderate population of massive stars create large cavities in their clouds over the course of less than one million years.
"Westerlund 1 hosts the most massive star population known in a galactic cluster, and it is at least 5 million years old, so it should have cleaned up all its clouds," Giuseppe said. "In the MIRI images, we think we are witnessing the accumulation of intracluster material from the gas and dust ejected by the most massive stars of the clusters during their final stages of evolution, and the interaction between the winds produced by different types of massive stars."
Giuseppe added that the MIRI images also revealed peculiar outflows and shells around the most evolved massive stars in Westerlund 1.
"In the next two to three years, we will publish most of the EWOCS science," Giuseppe said. The researcher explained that the next release will be a study of the hot intracluster gas in the cluster, studied by means of the diffuse emission in X-rays.
The EWOCS team will then release an analysis of high-energy phenomena happening in some of the compact objects in Westerlund 1 as well as calculate the mass distribution of low-mass stars in the cluster. The researchers also intend to analyze the disk-bearing population of the cluster, and conduct a study of outflows around the most evolved stars in the region, namely red supergiants and yellow hypergiants.
"That is just to mention a few. All these studies will be possible not only thanks to JWST but also other great observatories such as Chandra in X-rays, ALMA and Hubble," Giuseppe concluded. "Besides these, the analysis of the observations of Westerlund 2, a slightly less massive but younger cluster than Westerlund 1, is at a good stage, and we will start publishing those results soon."
The team's research has been accepted for publication in the journal Astronomy & Astrophysics and is available as a preprint on the repository site arXiv.
Quelle: SC
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Update: 6.12.2024
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Webb finds surprises in Spiderweb protocluster field
Using the NASA/ESA/CSA James Webb Space Telescope, an international team of astronomers have found new galaxies in the Spiderweb protocluster. Their characteristics reveal that new galaxies are forming in these large cosmic cities, with the finding that gravitational interactions in these dense regions are not as important as previously thought.
Astronomers explore galaxy populations and uncover their physical characteristics across large-scale structures to better understand the build-up of galaxies and how their environments shape their assembly. The Spiderweb protocluster is a well-studied object in the early Universe. Its light has travelled over 10 billion years to reach us, and it shows us a galaxy cluster in formation, composed of more than a hundred known galaxies.
With the use of Webb’s capabilities, astronomers have now sought to better understand this protocluster and to reveal new galaxies inside it. Infrared light passes more freely through cosmic dust than visible light, which is scattered by the dust. Because Webb can see well in the infrared, scientists used it to observe regions of the Spiderweb that were previously hidden to us by cosmic dust, and to find out to what degree this dust obscures them.
“We are observing the build-up of one the largest structures in the Universe, a city of galaxies in construction,” explained Jose M. Pérez-Martínez of the Instituto de Astrofísica de Canarias and the Universidad de La Laguna in Spain. “We know that most galaxies in local galaxy clusters (the biggest metropolises of the Universe) are old and not very active, whereas in this work we are looking at these objects during their adolescence. As this city in construction grows, their physical properties will also be affected. Now, Webb is giving us new insights into the build-up of such structures for the first time.”
With Webb, the team studied the hydrogen gas to reveal new, strongly obscured galaxies belonging to the cluster and to study how much they were obscured. This was accomplished using only about 3.5 hours of Webb’s observing time.
“As expected, we found new galaxy cluster members, but we were surprised to find more than expected,” explained Rhythm Shimakawa of Waseda University in Japan. “We found that previously-known galaxy members (similar to the typical star-forming galaxies like our Milky Way galaxy) are not as obscured or dust-filled as previously expected, which also came as a surprise.”
“This can be explained by the fact that the growth of these typical galaxies is not triggered primarily by galaxy interactions or mergers that induce star-formation,” added Helmut Dannerbauer of the Instituto de Astrofísica de Canarias in Spain. “We now figure this can instead be explained by star formation that is fueled through gas accumulating at different locations all across the object’s large-scale structure.”
The team is planning to study the (new) galaxy cluster members in more detail and confirm their existance with spectroscopic observations using Webb.
Notes for editors
The new results used Webb’s NIRCam observations (Cycle 1 programme #1572, PIs: H. Dannerbauer and Y. Koyama) and are featured in two papers that have been published today in the Astrophysical Journal: by R. Shimakawa et. al and by J. M. Pérez-Martínez et. al.
More information
Webb is the largest, most powerful telescope ever launched into space. Under an international collaboration agreement, ESA provided the telescope’s launch service, using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also provided the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.
Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).
Quelle: ESA
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Update: 11.12.2024
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NEW WEBB TELESCOPE VIEW SHOWS UNEXPECTEDLY CROWDED ASTEROID BELT
A new view of archival Webb telescope data reveals small asteroids in the main asteroid belt are more numerous than we thought.
Artist´s impression of an asteroid belt.
NASA / JPL-Caltech
Astronomers have uncovered an unexpectedly large population of small main-belt asteroids thanks to a new analysis of images from the James Webb Space Telescope. The finding could change calculations of the impact rate on Earth from such bodies, which range from house-size to the size of a stadium.
These are by far the smallest objects ever imaged so far away. Artem Burdanov (MIT) and colleagues applied a computationally intensive shift-and-stack method to Webb’s archival images. From the telescope’s sensitive infrared detectors, the team was able to accurately determine the sizes of small objects, ranging from about 10 to 500 meters (30 to 1,600 feet) across. An early release of their results appears in Nature.
Larger main-belt asteroids, whose orbits are between those of Mars and Jupiter, tend to remain in relatively stable orbits. However, gravitational interactions more frequently perturb smaller ones, which may enter the inner solar system to become potential impactors. The high number of small objects now found in the main belt — at least five times more than expected — could affect calculations of the frequency of such impacts.
Asteroids are primarily found with orbits between those of Mars and Jupiter. (This diagram also depicts asteroids with stable trajectories within Jupiter's orbit, known as Trojans.)
The shift and stack processing approach is used by professional and amateur astronomers alike to provide images of faint, fast-moving objects such as asteroids and comets. In this case, the astronomers used that method on steroids.
Usually, the idea is to move the telescope precisely in the direction and at the rate of motion of an object with a known orbit. Each frame maintains the target at the center, while background stars drift from frame to frame. Thus, even if an individual image doesn’t capture the object, dozens or even hundreds of frames can be added together, allowing the object to emerge from the random background noise that changes from frame to frame.
But the process usually depends on knowing the orbit. What if you don’t? That’s where harnessing a lot of computer power comes in. The team mined an archive of images from the JWST that had been gathered for a different purpose: studying the planets around the nearby star TRAPPIST-1. Because these images involved staring at the same small patch of sky over extended periods as much as 8 hours long, they turned out also to be useful for finding moving objects like asteroids.
To discover asteroids in unknown orbits, Burdanov used essentially a brute-force method, shifting in every possible direction and reasonable speed range for potential moving targets, then stacking those images.
“Since we have quite powerful computational tools — graphical processing units — we can do this search blindly,” Burdanov tells Sky & Telescope. “We decided to push the limits to see how faint objects we could find with this telescope,” he says.
This image shows a candidate moon of Jupiter, discovered with the popular shift-and-stack method. The moon appears as a dot of light at the center of the image, while background stars appear as streaks.
Edward Ashton (University of British Columbia)
Burdanov didn’t start out working on asteroids. He was already working with the data to study the TRAPPIST-1 exoplanets, it was natural to try looking for other things within that data. This project began in 2020, when he was still a graduate student, and as the COVID-19 pandemic began, he had the time to experiment. “Some people started to make sourdough, and I think doing asteroid work was an exoplanet person’s version of doing sourdough,” he says.
The initial blind search produced more than 1,000 candidates. Burdanov and co-researchers then narrowed down and confirmed clear evidence for 138 previously unknown asteroids, as well as eight known ones.
JWST is particularly good at finding asteroids, because they’re much brighter at infrared wavelengths. The astronomers constrained their diameters to within 10 to 20%, whereas estimates of size based on visible-light observations can vary by more than an order of magnitude. That’s because visible light comes from an asteroid’s reflection of sunlight, and therefore on how dark its surface is, a quality that can vary by a lot from object to object. The infrared light, on the other hand, results mostly from thermal emission, which won’t change much for a given object.
Infrared measurements could also provide measurements of objects’ shapes, since any variations in brightness would be due to shape rather than variations in surface reflectivity. However, the initial observations examined were too short to provide such information.
Finding so many small asteroids serendipitously, from one set of observations of one star taken for a different purpose, opens the prospect of mining a great deal more from other, similar JWST datasets. Planetary scientist Julien de Wit (MIT), a coauthor of the paper, says that the combination of JWST’s powerful infrared capabilities along with the power of the latest graphical processing units (GPUs) “would be truly transformative” in enabling the discovery of faint asteroids. “It’s a great example of computing technology that is used to enable a massive step forward with regard to exploration of the universe.” And, he adds, “there is so much of this astronomy data that is sitting in archives that could be mined,” that potentially thousands more small main-belt asteroids could remain to be found in those data.
Team member Richard Binzel (MIT) says, “These asteroid findings fill an important knowledge gap for tracing the source of meteorites and larger potentially hazardous asteroids in Earth's vicinity.”
Quelle: Sky&Telescope
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