NASA’s James Webb Space Telescope has enabled another long-sought scientific breakthrough, this time for solar system scientists studying the origins of Earth’s abundant water. Using Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, astronomers have confirmed gas – specifically water vapor – around a comet in the main asteroid belt for the first time, indicating that water ice from the primordial solar system can be preserved in that region. However, the successful detection of water comes with a new puzzle: unlike other comets, Comet 238P/Read had no detectable carbon dioxide.
This graphic presentation of spectral data highlights a key similarity and difference between observations of Comet 238P/Read by the NIRSpec (Near-Infrared Spectrograph) instrument on NASA’s James Webb Space Telescope in 2022 and observations of Comet 103P/Hartley 2 by NASA’s Deep Impact mission in 2010. Both show a distinct peak in the region of the spectrum associated with water. Finding this in Comet Read was a significant accomplishment for Webb, as it is in a different class of comets than Jupiter-family comets like Hartley 2, and this marks the first time that a gas has been confirmed in such a main belt comet. However, Comet Read did not show the characteristic, expected bump indicating the presence of carbon dioxide.
Credits: NASA, ESA, CSA, and J. Olmsted (STScI)
This artist’s concept of Comet 238P/Read shows the main belt comet sublimating—its water ice vaporizing as its orbit approaches the Sun. This is significant, as the sublimation is what distinguishes comets from asteroids, creating their distinctive tail and hazy halo, or coma. The James Webb Space Telescope’s detection of water vapor at Comet Read is a major benchmark in the study of main belt comets, and in the broader investigation of the origin of Earth’s abundant water.
Credits: NASA, ESA
“Our water-soaked world, teeming with life and unique in the universe as far as we know, is something of a mystery – we’re not sure how all this water got here,” said Stefanie Milam, Webb deputy project scientist for planetary science and a co-author on the study reporting the finding. “Understanding the history of water distribution in the solar system will help us to understand other planetary systems, and if they could be on their way to hosting an Earth-like planet,” she added.
Comet Read is a main belt comet – an object that resides in the main asteroid belt but which periodically displays a halo, or coma, and tail like a comet. Main belt comets themselves are a fairly new classification, and Comet Read was one of the original three comets used to establish the category. Before that, comets were understood to reside in the Kuiper Belt and Oort Cloud, beyond the orbit of Neptune, where their ices could be preserved farther from the Sun. Frozen material that vaporizes as they approach the Sun is what gives comets their distinctive coma and streaming tail, differentiating them from asteroids. Scientists have long speculated that water ice could be preserved in the warmer asteroid belt, inside the orbit of Jupiter, but definitive proof was elusive – until Webb.
“In the past, we’ve seen objects in the main belt with all the characteristics of comets, but only with this precise spectral data from Webb can we say yes, it’s definitely water ice that is creating that effect,” explained astronomer Michael Kelley of the University of Maryland, lead author of the study.
“With Webb’s observations of Comet Read, we can now demonstrate that water ice from the early solar system can be preserved in the asteroid belt,” Kelley said.
The missing carbon dioxide was a bigger surprise. Typically, carbon dioxide makes up about 10 percent of the volatile material in a comet that can be easily vaporized by the Sun’s heat. The science team presents two possible explanations for the lack of carbon dioxide. One possibility is that Comet Read had carbon dioxide when it formed but has lost that because of warm temperatures.
“Being in the asteroid belt for a long time could do it – carbon dioxide vaporizes more easily than water ice, and could percolate out over billions of years,” Kelley said. Alternatively, he said, Comet Read may have formed in a particularly warm pocket of the solar system, where no carbon dioxide was available.
This image of Comet 238P/Read was captured by the NIRCam (Near-Infrared Camera) instrument on NASA’s James Webb Space Telescope on September 8, 2022. It displays the hazy halo, called the coma, and tail that are characteristic of comets, as opposed to asteroids. The dusty coma and tail result from the vaporization of ices as the Sun warms the main body of the comet.
Credits: NASA, ESA, CSA, M. Kelley (University of Maryland). Image processing: H. Hsieh (Planetary Science Institute), A. Pagan (STScI)
The next step is taking the research beyond Comet Read to see how other main belt comets compare, says astronomer Heidi Hammel of the Association of Universities for Research in Astronomy (AURA), lead for Webb’s Guaranteed Time Observations for solar system objects and co-author of the study. “These objects in the asteroid belt are small and faint, and with Webb we can finally see what is going on with them and draw some conclusions. Do other main belt comets also lack carbon dioxide? Either way it will be exciting to find out,” Hammel said.
Co-author Milam imagines the possibilities of bringing the research even closer to home. “Now that Webb has confirmed there is water preserved as close as the asteroid belt, it would be fascinating to follow up on this discovery with a sample collection mission, and learn what else the main belt comets can tell us.”
THE JAMES WEBB SPACE TELESCOPE MAY HAVE SPOTTED A BABY GALAXY MERGER
New JWST images reveal that one of the most distant objects ever observed is actually two baby galaxies on a possible collision course.
The massive gravity of galaxy cluster MACS0647 acts as a cosmic lens to bend and magnify light from the more distant MACS0647-JD system. It also triply lensed the JD system, causing its image to appear in three separate locations. These images, which are highlighted with white boxes, are marked JD1, JD2, and JD3; zoomed-in views are shown in the panels at right. Science: NASA / ESA / CSA / Dan Coe (STScI) / Rebecca Larson (UT) / Yu-Yang Hsiao (JHU); Image processing: Alyssa Pagan (STScI)
Big galaxies like the Milky Way — a spiral disk 100,000 light years across containing some 200 billion stars — are thought to come from the celestial meet-and-greets of the first galaxies, which were originally little more than tiny clumps of stars. Now, the James Webb Space Telescope (JWST) has imaged two baby galaxies that existed just 430 million years after the Big Bang, each only hundreds of light-years across. Astronomers think they might be merging, shedding light on galaxy growth in the early universe.
“Most galaxies today will have been through several merger events,” says Tiger Yu-Yang Hsiao, (Johns Hopkins University), who led the study. “So [mergers] are key to studying the formation and evolution of galaxies today. Our target is from such an early time, right at the very beginning of this process. There is much we can learn from it.”
MACS0647–JD (MACS-JD) is an extremely distant object first observed about 10 years ago. At the time, it was considered to be the most distant galaxy ever observed, and it is still one of the earliest things we can study in detail with JWST.
Generally speaking, galaxies from the dawn of time are too faint and too far away to see. The reason we can see MACS-JD is because its light has been triply lensed, magnified and distorted by a massive galaxy cluster lying in front of it from our point of view. The cluster warps spacetime, splitting the light into three images of the same system. The images are magnified by factors of eight, five, and two, so they appear brighter than other galaxies at similar distances.
Hsiao’s JWST observations of MAC-JD verified previous conclusions about its distance, size, and physical properties — but with a surprising twist. What was once seen as a single object now appears to be two baby galaxies, labeled A and B. A is brighter and larger with very recent star formation and no dust, while B looks older and has a little bit of dust. Their differing star formation histories suggest they formed farther apart, only coming together recently.
“The researchers did a very good job approaching this problem, but there is a lot of uncertainty,” says Andrea Ferrara (Scuola Normale Superiore, Italy), who was not part of the study. He suggests that while a merger is a possibility, it’s also possible that one of the galaxies is a satellite of the other. Alternatively, the two components might be part of the same galaxy.
“We do expect that galaxies at this very high redshift are in the assembly process,” he notes, but he adds that additional data about the galaxies’ motions would help clarify their relationship.
Hsiao’s team based this study, posted on the arXiv and accepted to Astrophysical Journal Letters, solely on JWST images. Upcoming spectroscopic observations, also with JWST, should tell us how A and B are moving with respect to each other. If they are both part of the same galaxy, the difference between their velocities would be relatively small; if they are actually two merging galaxies, there would be a larger discrepancy. Besides shedding light on the objects’ motions, spectra will also tell us more about the chemical properties of these tiny, highly magnified galaxies observed in the early universe.
Quelle: Sky&Telescope
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Update: 20.05.2023
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JWST Will Hunt for Dead Solar Systems—And Much More—In Its Second Year of Science
White dwarfs, Earth-sized exoplanets, early galaxies and even Saturn’s moon Enceladus are on the agenda for JWST’s second year in space, but exomoons and others miss out
Where do you point the world’s most powerful space telescope? It’s not an easy question. The James Webb Space Telescope (JWST), launched in December 2021, has amazed astronomers since it began sending back its first science data in July 2022. It has seen galaxies breathtakingly close to the dawn of time, probed the atmospheres of exoplanets in unprecedented detail and provided stunning new views of worlds in our solar system. But it’s just getting started. Last week on May 10 astronomers learned if their proposals for the telescope’s second year of science were successful. Competition was fierce, and while there were plenty of winners and some incredible science set to be conducted, there were many more who missed out on JWST’s “Cycle 2,” which starts next month. “There was an extraordinary response from the science community,” says Nancy Levenson, interim director of the Space Telescope Science Institute (STScI) in Maryland, which runs JWST.
In total, astronomers submitted about 1,600 proposals to STScI for observing time on the NASA-led JWST. But only 249 were selected—meaning that JWST has an “oversubscription” of nearly 7 to 1, similar to that for the Hubble Space Telescope. To minimize the chance of bias, the process of selecting JWST’s programs is completely anonymous, with hundreds of astronomers from multiple subfields involved in the decision process. That said, there were clear winners and losers. Some astronomers, such as Nathan Adams of the University of Manchester in England, put forward multiple proposals that were rejected. “We had four proposals, and none of them got time,” Adams says. “Obviously we’re a bit disappointed.” Others, such as Mary Anne Limbach of Texas A&M University, were much more successful. Limbach had three proposals approved. “We’re excited about the time we got,” she says.
Limbach’s proposals are focused on white dwarfs, the remnant Earth-sized cores left behind after stars such as our sun swell into red giants and expel their outer layers. After this dramatic event, it’s thought these stellar corpses can still harbor intact planets—potentially offering us the chance to study them and learn more about the fate likely to befall Earth in five billion years when our sun enters its red giant phase. Limbach will attempt to confirm two suspected white dwarf worlds but will also search for up to a half dozen more elsewhere in the sky. “JWST can see if any of these nearby white dwarfs look brighter than they should be,” she says. “If they do, that could be an indicator there’s a planet there. JWST is really the only observatory capable of confirming them.”
A dominant area of JWST’s Cycle 1, which had about 1,200 proposals, was hunting for the earliest known galaxies in the universe, which were formed just a few hundred million years after the big bang. The same is true for Cycle 2, with both galaxies and exoplanets getting the most telescope time. An accepted proposal from Daniel Eisenstein of Harvard University is hoping to push JWST to its limits by hunting for galaxies perhaps up to just 200 million years post-big bang. Distances to faraway galaxies are measured in redshift—the degree to which light we see from a galaxy has been shifted to the red end of the spectrum by the universe’s expansion. Eisenstein will hunt for galaxies beyond redshift 15, farther than any others conclusively seen. “We don’t yet have a convincing case of a galaxy beyond redshift 15,” he says. “It’s really exciting to be able to continue the search that started in this first year.”
Rohan Naidu of the Massachusetts Institute of Technology will also be scouring the distant universe, but not for those highest-redshift galaxies. Instead, his program, which he co-leads with Jorryt Matthee of the Swiss Federal Institute of Technology in Zurich (ETH Zurich), will be using a giant cluster of galaxies called Abell 2744 to gravitationally magnify the light of some smaller objects up to 750 million years after the big bang. The goal is to look for clumps of primordial gas, which could contain clusters of Population III stars—the first stellar generation thought to have lit up the universe. These long-theorized objects have yet to be directly seen but are expected to be composed almost entirely of pure hydrogen and helium—which should allow them to be enormous, each weighing in hundreds of times heavier than our sun. “We’re really pushing JWST to the hilt,” Naidu says. “We’ll get back some very promising regions that might be hosting these clusters.”
A key target of interest for JWST’s Cycle 1 was the TRAPPIST-1 system, an arrangement of seven Earth-sized worlds—some of which might be habitable—around a red dwarf star about 40 light-years from Earth. While three TRAPPIST-1 programs were selected in Cycle 1, however, only one has been selected this time, led by Michaël Gillon of the University of Liège in Belgium. He will hunt for atmospheres on TRAPPIST-1b and c, the two innermost planets of the system. Early studies of TRAPPIST-1b suggest it has no atmosphere, but Gillon says his technique—measuring the temperature difference between the day and night side of the planet—will tell us for sure. That could have important implications for TRAPPIST-1’s other more temperate worlds that might conceivably support life. “If we can demonstrate that one of these two planets has an atmosphere, we will be in a very good position to ask for an ambitious program on JWST to dig into the other planets,” he says.
Closer to home, Christopher Glein of the Southwest Research Institute (SWRI) in Texas will use JWST to probe Saturn’s moon Enceladus, which may harbor a habitable ocean beneath its icy surface. Observations from NASA’s Cassini spacecraft, which orbited Saturn from 2004 to 2017, showed that the moon occasionally ejects water from this ocean via a plume at its south pole. While no spacecraft currently orbits Saturn, JWST is the next best thing. Incredibly, it will be able to “look for evidence of ocean chemistry” on the surface of Enceladus, Glein says. It will even be sensitive to certain substances, such as ammonia and various organic molecules, that could tell scientists about the habitability of the moon’s hidden ocean. In 2040 Enceladus’s south pole will enter a long winter of darkness that will last until 2055, making a potential future landing there to hunt for life difficult. Glein, however, is hoping to show with JWST that the moon’s polar plume is depositing frozen sea spray all across the surface, perhaps all the way up to the sunlit equator, where a landing could be more feasible. “JWST can act as a bridge between the Cassini era and a lander on Enceladus,” he says.
Not all areas of research were so lucky. David Kipping of Columbia University submitted two proposals to use JWST to hunt for moons orbiting exoplanets, known as exomoons. JWST “is the first machine humanity has ever built that is actually capable of doing this experiment,” Kipping says. But both proposals were rejected. “We’re definitely disappointed,” he says. “We really felt like this was a slam-dunk argument.”
JWST should be able to find exomoons down to the size of Europa, Kipping says, but even if it can’t, the results “would be pretty profound.” A failure to turn up an expected population of exomoons “would mean the models we use in our solar system aren’t universal,” he says, and could be a clue that our local abundance of lunar satellites is a bizarre deviation from cosmic norms. Time is of the essence, considering JWST is the only telescope now or for the foreseeable future that can look for exomoons. “JWST could last ten years, maybe longer,” Kipping notes. “If we never look for exomoons with it, we would really regret it. That would be such a shame.”
Levenson knows there will be some disappointment from the programs that were not selected. “There are lots of great ideas that we are not going to be able to observe during this cycle,” she says. For those that missed out, the deadline to try again and apply for Cycle 3 is October. “We have to keep trying,” Kipping says. “JWST is not going to be there forever.” For those lucky few that did make the cut, there are scientific riches to be had. “There’s this whole range of science that JWST is just great for,” says Levenson. “We’re definitely not done yet.”
Quelle: SCIENTIFIC AMERICAN
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Update: 29.05.2023
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James Webb telescope discovers gargantuan geyser on Saturn's moon, blasting water hundreds of miles into space
"It's immense," said Sara Faggi, a planetary astronomer at NASA's Goddard Space Flight Center.
An illustration of NASA's Cassini orbiter soaring through a giant vapor jet over the moon Enceladus (Image credit: NASA/JPL-Caltech)
Scientists caught Saturn's icy moon Enceladus spraying a "huge plume" of watery vapor far into space — and that plume likely contains many of the chemical ingredients for life.
Scientists detailed the eruption — glimpsed by the James Webb Space Telescope(JWST) in November 2022 — at a conference at the Space Telescope Science Institute in Baltimore on May 17.
"It's immense," Sara Faggi, a planetary astronomer at NASA's Goddard Space Flight Center, said at the conference, according to Nature.com. According to Faggi, a full research paper on the massive plume is pending.
This isn't the first time scientists have seen Enceladus spout water, but the new telescope's wider perspective and higher sensitivity showed that the jets of vapor shoot much farther into space than previously realized — many times deeper, in fact, than the width of Enceladus itself. (Enceladus has a diameter of about 313 miles, or 504 kilometers.)
Analysis revealed that the jets contained methane, carbon dioxide and ammonia — organic molecules containing chemical building blocks necessary for the development of life. It's even possible that some of these gases were produced by life itself, burping out methane deep beneath the surface of Enceladus, an international team of researchers posited in research published last year in The Planetary Science Journal.
Water is another piece of evidence in the case for possible life on Enceladus. Enceladus is totally encrusted in a thick layer of water ice, but measurements of the moon's rotation suggest that a vast ocean is hidden beneath that frozen crust. Scientists think the spurts of water sensed by JWST and Cassini come from hydrothermal vents in the ocean floor — a hypothesis supported by the presence of silica, a common ingredient in planetary crusts, in the vapor plumes.
NASA scientists are discussing future return missions to seek out signs of life on Enceladus. The proposed Enceladus Orbilander would orbit the moon for about six months, flying through its watery plumes and collecting samples. Then, the spacecraft would convert into a lander, descending on the surface of the icy moon. Orbilander would carry instruments to weigh and analyze molecules, as well as a DNA sequencer and a microscope. Cameras, radio sounders and lasers would remotely scan the moon's surface, The Planetary Society reported.
Another proposed mission involves sending an autonomous "snake robot" into the watery depths below Enceladus' surface. The robot, dubbed the Exobiology Extant Life Surveyor, features cameras and lidar on its head to help it navigate the unknown environment of Enceladus' ocean floor.
Quelle:SC
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Update: 31.05.2023
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Webb Maps Surprisingly Large Plume Jetting From Saturn’s Moon Enceladus
A water vapor plume from Saturn’s moon Enceladus spanning more than 6,000 miles – nearly the distance from Los Angeles, California to Buenos Aires, Argentina – has been detected by researchers using NASA’s James Webb Space Telescope. Not only is this the first time such a water emission has been seen over such an expansive distance, but Webb is also giving scientists a direct look, for the first time, at how this emission feeds the water supply for the entire system of Saturn and its rings.
Enceladus, an ocean world about four percent the size of Earth, just 313 miles across, is one of the most exciting scientific targets in our solar system in the search for life beyond Earth. Sandwiched between the moon’s icy outer crust and its rocky core is a global reservoir of salty water. Geyser-like volcanos spew jets of ice particles, water vapor, and organic chemicals out of crevices in the moon’s surface informally called ‘tiger stripes.’
Previously, observatories have mapped jets hundreds of miles from the moon’s surface, but Webb’s exquisite sensitivity reveals a new story.
In this image, NASA’s James Webb Space Telescope shows a water vapor plume jetting from the southern pole of Saturn’s moon Enceladus, extending out 20 times the size of the moon itself. The inset, an image from the Cassini orbiter, emphasizes how small Enceladus appears in the Webb image compared to the water plume.
Credits: NASA, ESA, CSA, STScI, and G. Villanueva (NASA’s Goddard Space Flight Center). Image Processing: A. Pagan (STScI).
“When I was looking at the data, at first, I was thinking I had to be wrong. It was just so shocking to detect a water plume more than 20 times the size of the moon,” said lead author Geronimo Villanueva of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The water plume extends far beyond its release region at the southern pole.”
The length of the plume was not the only characteristic that intrigued researchers. The rate at which the water vapor is gushing out, about 79 gallons per second, is also particularly impressive. At this rate, you could fill an Olympic-sized swimming pool in just a couple of hours. In comparison, doing so with a garden hose on Earth would take more than 2 weeks.
The Cassini orbiter spent over a decade exploring the Saturnian system, and not only imaged the plumes of Enceladus for the first time but flew directly through them and sampled what they were made of. While Cassini’s position within the Saturnian system provided invaluable insights into this distant moon, Webb’s unique view from the Sun-Earth Lagrange Point 2 one million miles from Earth, along with the remarkable sensitivity of its Integral Field Unit aboard the NIRSpec (Near-Infrared Spectrograph) Instrument, is offering new context.
“The orbit of Enceladus around Saturn is relatively quick, just 33 hours. As it whips around Saturn, the moon and its jets are basically spitting off water, leaving a halo, almost like a donut, in its wake,” said Villanueva. “In the Webb observations, not only was the plume huge, but there was just water absolutely everywhere.”
This fuzzy donut of water that appeared ‘everywhere,’ described as a torus, is co-located with Saturn’s outermost and widest ring – the dense “E-ring.”
The Webb observations directly demonstrate how the moon’s water vapor plumes feed the torus. By analyzing the Webb data, astronomers have determined roughly 30 percent of the water stays within this torus, and the other 70 percent escapes to supply the rest of the Saturnian system of water.
In the coming years, Webb will serve as the primary observation tool for ocean moon Enceladus, and discoveries from Webb will help inform future solar system satellite missions that will look to explore the subsurface ocean’s depth, how thick the ice crust is, and more.
In this image, NASA’s James Webb Space Telescope’s instruments are revealing details into how one of Saturn’s moon’s feeds a water supply to the entire system of the ringed planet. New images from Webb’s NIRSpec (Near-Infrared Spectrograph) have revealed a water vapor plume jetting from the southern pole of Enceladus, extending out more than 20 times the size of the moon itself. The Integral Field Unit (IFU) aboard NIRSpec also provided insights into how the water from Enceladus feeds the rest of its surrounding environment.
Credits: NASA, ESA, CSA, STScI, Leah Hustak (STScI)
“Right now, Webb provides a unique way to directly measure how water evolves and changes over time across Enceladus' immense plume, and as we see here, we will even make new discoveries and learn more about the composition of the underlying ocean,” added co-author Stefanie Milam at NASA Goddard. “Because of Webb’s wavelength coverage and sensitivity, and what we’ve learned from previous missions, we have an entire new window of opportunity in front of us.”
Webb’s observations of Enceladus were completed under Guaranteed Time Observation (GTO) program 1250. The initial goal of this program is to demonstrate the capabilities of Webb in a particular area of science and set the stage for future studies.
“This program was essentially a proof of concept after many years of developing the observatory, and it’s just thrilling that all this science has already come out of quite a short amount of observation time,” said Heidi Hammel of the Association of Universities for Research in Astronomy, Webb interdisciplinary scientist and leader of the GTO program.
The team’s results were recently accepted for publication in Nature Astronomy on May 17, and a pre-print is available here.
Quelle: NASA
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Update: 2.06.2023
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Discovery Alert: Webb Maps and Finds Traces of Water in an Ultra-hot Gas Giant's Atmosphere
WASP-18 b, seen in an artist concept, is a gas giant exoplanet 10 times more massive than Jupiter that orbits its star in just 23 hours. Researchers used NASA’s James Webb Space Telescope to study the planet as it moved behind its star. Temperatures there reach 5,000 degrees Fahrenheit (2,700 C). Credit: NASA/JPL-Caltech (K. Miller/IPAC)
There’s an intriguing exoplanet out there – 400 light-years out there – that is so tantalizing that astronomers have been studying it since its discovery in 2009. A year for WASP-18 b, one orbit around its star (slightly larger than our Sun), takes just 23 hours. There’s nothing like it in our solar system. In addition to observatories on the ground, NASA’s Hubble, Chandra, TESS, and Spitzer space telescopes have all observed WASP-18 b, an ultra-hot gas giant 10 times more massive than Jupiter. Now astronomers have taken a look with NASA’s James Webb Space Telescope and the ‘‘firsts’’ keep coming.
The discovery: Scientists identified water vapor in the atmosphere of WASP-18 b, and made a temperature map of the planet as it slipped behind, and reappeared from, its star. This event is known as a secondary eclipse. Scientists can read the combined light from star and planet, then refine the measurements from just the star as the planet moves behind it.
The same side, known as the dayside, of WASP-18 b always faces the star, just as the same side of the Moon always faces Earth. The temperature, or brightness, map shows a huge change in temperature – up to 1,000 degrees – from the hottest point facing the star to the terminator, where day and night sides of the tidally-locked planet meet in permanent twilight.
Researchers made a brightness map, tracing the glow from hot regions of WASP-18 b as it slipped behind, and reappeared from, its star. This event is known as a secondary eclipse. Scientists can measure the combined light from star and planet, then measure the light from just the star as the planet moves behind it. The plot is a light curve, the measured change in brightness of a star as a planet moves in front of or behind it. The planet’s brightness map, obtained using NASA’s James Webb Space Telescope, allowed researchers to determine a temperature map of the planet’s atmosphere. Credit: NASA/JPL-Caltech (K. Miller/IPAC)
‘‘JWST is giving us the sensitivity to make much more detailed maps of hot giant planets like WASP-18 b than ever before. This is the first time a planet has been mapped with JWST, and it’s really exciting to see that some of what our models predicted, such as a sharp drop in temperature away from the point on the planet directly facing the star, is actually seen in the data!’’ said Megan Mansfield, a Sagan Fellow at the University of Arizona, and one of the authors of the paper describing the results.
The team mapped temperature gradients across the day side of the planet. Given how much cooler the planet is at the terminator, there is likely something hindering winds from efficiently redistributing heat to the night side. But what is affecting the winds is still a mystery.
‘‘The brightness map of WASP-18 b shows a lack of east-west winds that is best matched by models with atmospheric drag. One possible explanation is that this planet has a strong magnetic field, which would be an exciting discovery!’’ said co-author Ryan Challener, of the University of Michigan.
One interpretation of the eclipse map is that magnetic effects force the winds to blow from the planet’s equator up over the North pole and down over the South pole, instead of East-West, as we would otherwise expect.
Researchers recorded temperature changes at different elevations of the gas giant planet’s layers of atmosphere. They saw temperatures increase with elevation, varying by hundreds of degrees.
The spectrum of the planet’s atmosphere clearly shows multiple small but precisely measured water features, present despite the extreme temperatures of almost 5,000 degrees Fahrenheit (2,700 C). It’s so hot that it would tear most water molecules apart, so still seeing its presence speaks to Webb’s extraordinary sensitivity to detect remaining water. The amounts recorded in WASP-18 b’s atmosphere indicate water vapor is present at various elevations.
The team obtained the thermal emission spectrum of WASP-18 b by measuring the amount of light it emits over NASA’s James Webb Space Telescope’s NIRISS SOSS 0.85-2.8 um wavelength range, capturing 65% of the total energy emitted by the planet. WASP-18 b is so hot on the day side of this tidally-locked planet (the same side always faces its star, as the Moon to Earth) that water vapor molecules would break apart. The Webb Telescope directly observed water vapor on the planet in even relatively small amounts, indicating the sensitivity of the observatory. Credit: NASA/JPL-Caltech (R. Hurt/IPAC)
‘‘It was a great feeling to look at WASP-18 b’s JWST spectrum for the first time and see the subtle but precisely measured signature of water,’’ said Louis-Philippe Coulombe, a graduate student at the University of Montreal and lead author of the WASP-18 b paper. ‘‘Using such measurements, we will be able to detect such molecules for a wide range of planets in the years to come!’’
Researchers looked at WASP-18 b for about six hours with one of Webb’s instruments, the Near-Infrared Imager and Slitless Spectrograph (NIRISS), contributed by the Canadian Space Agency.
‘‘Because the water features in this spectrum are so subtle, they were difficult to identify in previous observations. That made it really exciting to finally see water features with these JWST observations,’’ said Anjali Piette, a postdoctoral fellow at the Carnegie Institution for Science and one of the authors of the new research.
The discoverers: More than 100 scientists around the globe are working on early science from Webb through the Transiting Exoplanet Community Early Release Science Program led by Natalie Batalha, an astronomer at the University of California, Santa Cruz, who helped coordinate the new research. Much of this groundbreaking work is being done by early career scientists like Coulombe, Challener, Piette, and Mansfield.
Proximity, both to its star and to us, helped make WASP-18 b such an intriguing target for scientists, as did its large mass. WASP-18 b is one of the most massive worlds whose atmospheres we can investigate. We want to know how such planets form and come to be where they are. This, too, has some early answers from Webb.
‘‘By analyzing WASP-18b’s spectrum, we not only learn about the various molecules that can be found in its atmosphere but also about the way it formed. We find from our observations that WASP-18 b’s composition is very similar to that of its star, meaning it most likely formed from the leftover gas that was present just after the star was born,’’ Coulombe said. ‘‘Those results are very valuable to get a clear picture of how strange planets like WASP-18 b, which have no counterpart in our solar system, come to exist.’’
Scientists used the James Webb Space Telescope to observe the exoplanet WASP-18 b and its star before, during and after the planet was eclipsed. By measuring the change in light when the planet travels behind the star, the planet’s brightness is revealed. From these measurements, scientists were able to make a temperature map of the planet’s day side. Displayed temperature range: 2,800 to 4,800 degrees Fahrenheit (1,500 to 2,600 degrees Celsius). Credit: NASA/JPL-Caltech (R. Hurt/IPAC)
Quelle: NASA
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Update: 6.06.2023
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Webb peers behind bars
A close-in image of a spiral galaxy, showing its core and part of a spiral arm. Thousands upon thousands of tiny stars that make it up can be seen, most dense in a whitish bar that forms its core. Clumps and filaments of dust form an almost skeletal structure that follows the twist of the galaxy and its spiral arm. Large, glowing bubbles of red gas are hidden in the dust.
A delicate tracery of dust and bright star clusters threads across this image from the NASA/ESA/CSA James Webb Space Telescope. The bright tendrils of gas and stars belong to the barred spiral galaxy NGC 5068, whose bright central bar is visible in the upper left of this image. NGC 5068 lies around 17 million light-years from Earth in the constellation Virgo.
This portrait of NGC 5068 is part of a campaign to create an astronomical treasure trove, a repository of observations of star formation in nearby galaxies. Previous gems from this collection can be seen here and here. These observations are particularly valuable to astronomers for two reasons.
The first is because star formation underpins so many fields in astronomy, from the physics of the tenuous plasma that lies between stars to the evolution of entire galaxies. By observing the formation of stars in nearby galaxies, astronomers hope to kick-start major scientific advances with some of the first available data from Webb.
The second reason is that Webb's observations build on other studies using telescopes including the NASA/ESA Hubble Space Telescope and some of the world's most capable ground-based observatories.
Webb collected images of 19 nearby star-forming galaxies which astronomers could then combine with catalogues from Hubble of 10 000 star clusters, spectroscopic mapping of 20 000 star-forming emission nebulae from the Very Large Telescope (VLT), and observations of 12 000 dark, dense molecular clouds identified by the Atacama Large Millimeter/submillimeter Array (ALMA). These observations span the electromagnetic spectrum and give astronomers an unprecedented opportunity to piece together the minutiae of star formation.
With its ability to peer through the gas and dust enshrouding newborn stars, Webb is the perfect telescope to explore the processes governing star formation. Stars and planetary systems are born amongst swirling clouds of gas and dust that are opaque to observations in visible light, like many from Hubble or the VLT.
The keen vision at infrared wavelengths of two of Webb's instruments - MIRI and NIRCam - allowed astronomers to see right through the gargantuan clouds of dust in NGC 5068 and capture the processes of star formation as they happened. This image combines the capabilities of these two instruments, providing a truly unique look at the composition of NGC 5068.
Quelle: SD
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Update: 7.06.2023
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JWST spots the most distant ‘smoke’ molecules ever seen in space
The presence of the molecules in an early galaxy means it must have pumped out stars at a furious pace, researchers say.
A galaxy (blue; artificially coloured) helped to give the JWST a better view of organic molecules (bright orange spots) in a second galaxy.Credit: J. Spilker/S. Doyle, NASA, ESA, CSA
Tangles of huge organic molecules are drifting through a faraway galaxy, astronomers using the James Webb Space Telescope (JWST) have discovered. Scientists have never spotted such molecules so far from Earth, and their presence suggests that their host galaxy was busy creating stars early in the history of the Universe.
Spilker and his colleagues describe the finding today in Nature1. It shows the power of the new JWST, even as the spectrometer aboard the telescope that made the measurement has experienced a sudden and surprising degradation in performance.
Photobombing galaxy
As seen from Earth, the galaxy, known as SPT0418-47, happens to lie behind another, closer galaxy. The gravity of the intervening galaxy bends and distorts the light from SPT0418-47, making it some 30 times brighter than it would otherwise appear — an effect called gravitational lensing.
Spilker’s team wanted to find polycyclic aromatic hydrocarbons (PAHs), which are chemical compounds that are found in soot and smoke. They also form near young, massive stars that emit a lot of ultraviolet light.
Feeding off that energy, the molecules grow large and eventually resemble smoke or soot particles floating in space. They help to regulate how gas within galaxies is heated and cooled, and thus help to control how new stars are born, says Stacey Alberts, an astronomer at the University of Arizona in Tucson.
Earlier studies of SPT0418-47 had spotted areas where stars might have been forming, but could not detect PAHs2. The molecules are hard to spot except in infrared wavelengths of light, which JWST excels at studying. So Spilker’s team pointed the telescope at the galaxy last August, in what were some of its first science observations. Months later, they finally had the data processed, and the PAHs emerged.
The molecules appear as bright patches inside the galaxy’s ring. That patchiness surprised Spilker. “Everywhere we see the molecules there are stars forming — but there are also parts in that ring where there are stars forming where we don’t see the molecules,” he says. “That’s the part we don’t really understand yet.”
Regardless, the PAHs suggest that the galaxy was busy making stars early in the Universe’s history. At a time when the Universe was just 10 percent of its current age, SPT0418-47 already had a mass similar to that of today’s Milky Way.
Other JWST observations have spotted PAHs in nearby galaxies3. But seeing PAHs in this distant galaxy is an important clue to how these molecules form, says Karin Sandstrom, an astronomer at the University of California San Diego. They are “quite mysterious still, and we don’t fully understand how they form even in the Milky Way”, she says. Alberts adds that the new discovery will force astronomers to “rethink how dust first formed and how that shaped the early generations of stars and galaxies”.
More discoveries might be on the way — or not. Spilker and his colleagues are planning to use JWST to hunt for PAHs in two other gravitationally lensed galaxies. But the telescope’s mid-infrared spectrometer, which is what the team used to study SPT0418-47, is currently experiencing problems.
On 25 May, the team that operates JWST reported that the spectrometer was not gathering as much information as it is supposed to in one of the modes in which it operates. Two of the four channels in which it observes in that mode are degrading, in the worst case losing up to 50% of the data.
“The root cause of this issue is still under investigation,” the engineers wrote. The spectrometer continues to operate, but “the team has worked on carefully quantifying the effect of this loss on science data”.
