James Webb Space Telescope captures chaotic cosmic collision
Webb caught sight of a galactic get-together known as II ZW 96.
The James Webb Space Telescope has captured a pair of galaxies distorting each other as they merge in a great galactic get-together.
The ongoing cosmic collision imaged by Webb is known as II ZW 96. It is roughly 500 million light-years from Earth and located in the constellation Delphinus, according to a Nov. 30 NASA statement(opens in new tab).
The image was created by Webb bringing to bear its cutting-edge NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) payloads on II ZW 96 and details how the shape of both galaxies are being distorted by their respective gravitational attraction.
(Image credit: ESA/Webb, NASA & CSA, L. Armus, A. Evans)
NASA scientists note that the spiral arms of the lower galaxy have been twisted out of shape, while the bright cores of both galaxies are connected by the very bright tendrils of star-forming regions that made II ZW 96 such a tempting target for Webb.
The observation is a part of a wider effort by Webb to examine how galaxies evolve, focusing particular on nearby so-called Luminous Infrared Galaxies. These galaxies — of which II ZW 96 is an example — are particularly bright at infrared wavelengths, with luminosities more than 100 billion times that of the sun, according to NASA.
James Webb Space Telescope spies Milky Way mimics that could challenge theories of galaxy evolution
Galaxies similar to our own Milky Way sprouted up earlier than scientists expected.
(Image credit: NASA/CEERS/University of Texas at Austin)
James Webb Space Telescope keeps surprising us.
A key advantage of the James Webb Space Telescope (JWST) is its ability to peer deep into the past. By looking in the infrared part of the electromagnetic spectrum, it's able to see light that has taken billions of years to reach us, stretched out by the expanding universe along its journey.
JWST's specialized eyes on the universe recently revealed yet another surprise —multiple galaxies that look like our Milky Way, but from between 8 and 11 billion years in the past when the universe was much younger.
New research described in a statement from UT Austin(opens in new tab) presents observations from the JWST Cosmic Evolution Early Release Science Survey(opens in new tab) showing galaxies with stellar bars, straight lines of stars stretching from galactic centers to their outer disks, at this time in the young universe. The discovery could "require scientists to refine their theories of galaxy evolution," according to the statement.
"I took one look at these data, and I said, 'We are dropping everything else!'" Shardha Jogee, an astronomer at UT Austin, said in the statement.
This is the first time stellar bars have been observed in such young galaxies, challenging existing models of how galaxies form and grow. They may also help astronomers answer existing questions about galaxies, such as how supermassive black holes in galactic centers grow and how galaxies get enough material to make stars in their centers, known as the supply chain problem.
"For this study, we are looking at a new regime where no one had used this kind of data or done this kind of quantitative analysis before," added lead author Yuchen Guo. "So everything is new. It's like going into a forest that nobody has ever gone into."
Jogee added that these stellar bars could "solve the supply chain problem in galaxies."
"Just like we need to bring raw material from the harbor to inland factories that make new products, a bar powerfully transports gas into the central region where the gas is rapidly converted into new stars at a rate typically 10 to 100 times faster than in the rest of the galaxy," Jogee explained.
This discovery is yet another testament to the extraordinary capabilities of NASA's new workhorse space telescope, and a step towards understanding how galaxies like our Milky Way came to be.
The research is published in The Astrophysical Journal Letters(opens in new tab).
NASA’s Webb Telescope Reveals Links Between Galaxies Near and Far
A new analysis of distant galaxies imaged by NASA’s James Webb Space Telescope shows that they are extremely young and share some remarkable similarities to “green peas,” a rare class of small galaxies in our cosmic backyard.
“With detailed chemical fingerprints of these early galaxies, we see that they include what might be the most primitive galaxy identified so far. At the same time, we can connect these galaxies from the dawn of the universe to similar ones nearby, which we can study in much greater detail,” said James Rhoads, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who presented the findings at the 241st meeting of the American Astronomical Society in Seattle.
A paper describing the results, led by Rhoads, was published Jan. 3 in The Astrophysical Journal Letters.
Green pea galaxies were discovered and named in 2009 by volunteers taking part in Galaxy Zoo, a project where citizen scientists help classify galaxies in images, starting with those from the Sloan Digital Sky Survey. Peas stood out as small, round, unresolved dots with a distinctly green shade, a consequence of both the colors assigned to different filters in the survey’s composite images and a property of the galaxies themselves.
Green pea galaxy colors are unusual because a sizable fraction of their light comes from brightly glowing gas clouds. The gases emit light at specific wavelengths – unlike stars, which produce a rainbow-like spectrum of continuous color. Peas are also quite compact, typically only about 5,000 light-years across or about 5% the size of our Milky Way galaxy.
“Peas may be small, but their star-formation activity is unusually intense for their size, so they produce bright ultraviolet light,” said Keunho Kim, a postdoctoral researcher at the University of Cincinnati and a member of the analysis team. “Thanks to ultraviolet images of green peas from Hubble and ground-based research on early star-forming galaxies, it’s clear that they both share this property.”
In July 2022, NASA and its partners in the Webb mission released the deepest and sharpest infrared image of the distant universe yet seen, capturing thousands of galaxies in and behind a cluster known as SMACS 0723. The cluster’s mass makes it a gravitational lens, which both magnifies and distorts the appearance of background galaxies. Among the faintest galaxies behind the cluster were a trio of compact infrared objects that looked like they could be distant relatives of green peas. The most distant of these three galaxies was magnified by about 10 times, providing a significant assist from nature on top of the telescope’s unprecedented capabilities.
Webb did more than image the cluster – its Near-Infrared Spectrograph (NIRSpec) instrument also captured the spectra of selected galaxies in the scene. When Rhoads and his colleagues examined these measurements and corrected them for the wavelength stretch resulting from the expansion of space, they saw characteristic features emitted by oxygen, hydrogen, and neon line up in a stunning resemblance to those seen from nearby green peas.
Additionally, the Webb spectra made it possible to measure the amount of oxygen in these cosmic dawn galaxies for the first time.
As stars produce energy, they transmute lighter elements like hydrogen and helium into heavier ones. When stars explode or lose their outer layers at the ends of their lives, these heavier elements become incorporated into the gas that forms the next stellar generations, and the process continues. Over cosmic history, stars have steadily enriched the universe.
Two of the Webb galaxies contain oxygen at about 20% of the level in our Milky Way. They resemble typical green peas, which nevertheless make up less than 0.1% of the nearby galaxies observed by the Sloan survey. The third galaxy studied is even more unusual.
“We’re seeing these objects as they existed up to 13.1 billion years ago, when the universe was about 5% its current age,” said Goddard researcher Sangeeta Malhotra. “And we see that they are young galaxies in every sense – full of young stars and glowing gas that contains few chemical products recycled from earlier stars. Indeed, one of them contains just 2% the oxygen of a galaxy like our own and might be the most chemically primitive galaxy yet identified.”
NIRSpec was built for ESA (European Space Agency) by Airbus Industries. Its array of nearly half a million microshutters – tiny doors that can be opened or closed to admit or block light – allow it to capture spectra of up to 100 individual objects at a time. The microshutter array and detector subsystems were fabricated by NASA.
The James Webb Space Telescope, an international mission led by NASA with its partners ESA and CSA (Canadian Space Agency), is the world's premier space science observatory. NASA Headquarters oversees the mission for the agency’s Science Mission Directorate. NASA’s Goddard Space Flight Center manages Webb for the agency and oversees work on the mission performed by the Space Telescope Science Institute, Northrop Grumman, and other mission partners. In addition to Goddard, several NASA centers contributed to the project, including the agency’s Johnson Space Center in Houston, Jet Propulsion Laboratory in Southern California, Marshall Space Flight Center in Huntsville, Alabama, Ames Research Center in California’s Silicon Valley, and others.
Banner image: Three faint, small, distant galaxies (in boxes) appear in the James Webb Space Telescope’s deep image of the galaxy cluster SMACS 0723. Measurements show they exhibit properties linking them to rare galaxies known as “green peas” found nearby. Credit: NASA, ESA, CSA, and STScI
NASA’s Webb Telescope Awarded Robert H. Goddard Memorial Trophy
The team behind NASA’s James Webb Space Telescope has been selected to receive the 2023 Robert H. Goddard Memorial Trophy, the premier award from the National Space Club and Foundation. This annual award honors an individual, group, or program deemed by the Club to have made the most significant contribution to space activity in the previous year.
The award will be presented at the Club’s yearly Dr. Robert H. Goddard Memorial Dinner in Washington on March 10, 2023
In 2022, the Webb team successfully completed an intricate series of deployments to unfold the observatory into its final configuration in space. They then precisely aligned its mirrors to within nanometers, set up and tested its powerful instruments, and officially began Webb’s mission to explore the infrared universe.
With its optics performing nearly twice as well as the mission required, Webb has already spotted some of the earliest galaxies ever observed, peered through dusty clouds to see stars forming, and provided a more detailed look at the atmospheres of planets outside our solar system than ever before. The Goddard Trophy will recognize the contributions of the team that designed, developed, and now operate Webb, including individuals from NASA’s Goddard Space Flight Center, Greenbelt, Maryland; Northrop Grumman, Redondo Beach, California; the Space Telescope Science Institute, Baltimore; and Ball Aerospace, Boulder, Colorado. The mission was also made possible by many international contributions from partnerships with ESA (European Space Agency) and CSA (Canadian Space Agency).
“Our team designed the James Webb Space Telescope to see the first lights that illuminated our universe,” said Mike Menzel, NASA Mission Systems Engineer for the Webb at the Goddard Space Flight Center in Greenbelt, Maryland. “This required the largest ‘first of its kind’ telescope ever put into space along with 50 of the most complex deployments ever attempted to essentially re-build it on-orbit. After all these many years and many engineering challenges our team was struck with awe and wonder at the first images, and the satisfaction of knowing that whatever is out there we will see it.”
Recent winners of the Goddard Memorial Trophy include the teams behind NASA’s Ingenuity Mars Helicopter, New Horizons, and Kepler mission.
Webb, an international mission led by NASA with its partners ESA (European Space Agency) and CSA (Canadian Space Agency), is the world’s premier space science observatory. Its design pushed the boundaries of space telescope capabilities to solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.
NASA Headquarters, Washington oversees the Webb telescope mission. NASA Goddard manages Webb for the agency and oversees work on the mission performed by the Space Telescope Science Institute, Northrop Grumman, and other mission partners. In addition to Goddard, several NASA centers contributed to the project, including the agency’s Johnson Space Center in Houston, Jet Propulsion Laboratory in southern California, Marshall Space Flight Center in Huntsville, Alabama, Ames Research Center in California’s Silicon Valley, and others.
NASA’s Webb Uncovers Star Formation in Cluster’s Dusty Ribbons
NGC 346, one of the most dynamic star-forming regions in nearby galaxies, is full of mystery. Now, it is less mysterious with new findings from NASA’s James Webb Space Telescope.
NCG 346 is located in the Small Magellanic Cloud (SMC), a dwarf galaxy close to our Milky Way. The SMC contains lower concentrations of elements heavier than hydrogen or helium, which astronomers call metals, compared to the Milky Way. Since dust grains in space are composed mostly of metals, scientists expected there would be low amounts of dust, and that it would be hard to detect. New data from Webb reveals the opposi
Astronomers probed this region because the conditions and amount of metals within the SMC resemble those seen in galaxies billions of years ago, during an era in the universe known as “cosmic noon,” when star formation was at its peak. Some 2 to 3 billion years after the big bang, galaxies were forming stars at a furious rate. The fireworks of star formation happening then still shape the galaxies we see around us today.
“A galaxy during cosmic noon wouldn’t have one NGC 346 like the Small Magellanic Cloud does; it would have thousands” of star-forming regions like this one, said Margaret Meixner, an astronomer at the Universities Space Research Association and principal investigator of the research team. “But even if NGC 346 is now the one and only massive cluster furiously forming stars in its galaxy, it offers us a great opportunity to probe conditions that were in place at cosmic noon.”
By observing protostars still in the process of forming, researchers can learn if the star formation process in the SMC is different from what we observe in our own Milky Way. Previous infrared studies of NGC 346 have focused on protostars heavier than about 5 to 8 times the mass of our Sun. “With Webb, we can probe down to lighter-weight protostars, as small as one tenth of our Sun, to see if their formation process is affected by the lower metal content,” said Olivia Jones of the United Kingdom Astronomy Technology Centre, Royal Observatory Edinburgh, a co-investigator on the program.
As stars form, they gather gas and dust, which can look like ribbons in Webb imagery, from the surrounding molecular cloud. The material collects into an accretion disk that feeds the central protostar. Astronomers have detected gas around protostars within NGC 346, but Webb’s near-infrared observations mark the first time they have also detected dust in these disks.
“We’re seeing the building blocks, not only of stars, but also potentially of planets,” said Guido De Marchi of the European Space Agency, a co-investigator on the research team. “And since the Small Magellanic Cloud has a similar environment to galaxies during cosmic noon, it’s possible that rocky planets could have formed earlier in the universe than we might have thought.”
The team also has spectroscopic observations from Webb’s NIRSpec instrument that they are continuing to analyze. These data are expected to provide new insights into the material accreting onto individual protostars, as well as the environment immediately surrounding the protostar.
These results are being presented Jan. 11 in a press conference at the 241st meeting of the American Astronomical Society. The observations were obtained as part of program 1227.
The James Webb Space Telescope is the world's premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
New Webb Image Reveals Dusty Disk Like Never Seen Before
NASA’s James Webb Space Telescope has imaged the inner workings of a dusty disk surrounding a nearby red dwarf star. These observations represent the first time the previously known disk has been imaged at these infrared wavelengths of light. They also provide clues to the composition of the disk.
The star system in question, AU Microscopii or AU Mic, is located 32 light-years away in the southern constellation Microscopium. It’s approximately 23 million years old, meaning that planet formation has ended since that process typically takes less than 10 million years. The star has two known planets, discovered by other telescopes. The dusty debris disk that remains is the result of collisions between leftover planetesimals – a more massive equivalent of the dust in our solar system that creates a phenomenon known as zodiacal light.
“A debris disk is continuously replenished by collisions of planetesimals. By studying it, we get a unique window into the recent dynamical history of this system,” said Kellen Lawson of NASA’s Goddard Space Flight Center, lead author on the study and a member of the research team that studied AU Mic.
“This system is one of the very few examples of a young star, with known exoplanets, and a debris disk that is near enough and bright enough to study holistically using Webb’s uniquely powerful instruments,” said Josh Schlieder of NASA’s Goddard Space Flight Center, principal investigator for the observing program and a study co-author.
The team used Webb’s Near-Infrared Camera (NIRCam) to study AU Mic. With the help of NIRCam's coronagraph, which blocks the intense light of the central star, they were able to study the region very close to the star. The NIRCam images allowed the researchers to trace the disk as close to the star as 5 astronomical units (460 million miles) – the equivalent of Jupiter’s orbit in our solar system.
“Our first look at the data far exceeded expectations. It was more detailed than we expected. It was brighter than we expected. We detected the disk closer in than we expected. We're hoping that as we dig deeper, there's going to be some more surprises that we hadn't predicted,” stated Schlieder.
The observing program obtained images at wavelengths of 3.56 and 4.44 microns. The team found that the disk was brighter at the shorter wavelength, or “bluer,” likely meaning that it contains a lot of fine dust that is more efficient at scattering shorter wavelengths of light. This finding is consistent with the results of prior studies, which found that the radiation pressure from AU Mic — unlike that of more massive stars — would not be strong enough to eject fine dust from the disk.
While detecting the disk is significant, the team’s ultimate goal is to search for giant planets in wide orbits, similar to Jupiter, Saturn, or the ice giants of our solar system. Such worlds are very difficult to detect around distant stars using either the transit or radial velocity methods.
“This is the first time that we really have sensitivity to directly observe planets with wide orbits that are significantly lower in mass than Jupiter and Saturn. This really is new, uncharted territory in terms of direct imaging around low-mass stars,” explained Lawson.
These results are being presented today in a press conference at the 241st meeting of the American Astronomical Society. The observations were obtained as part of Webb’s Guaranteed Time program 1184.
The James Webb Space Telescope is the world's premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
NASA’s Webb Confirms Its First Exoplanet
Researchers confirmed an exoplanet, a planet that orbits another star, using NASA’s James Webb Space Telescope for the first time. Formally classified as LHS 475 b, the planet is almost exactly the same size as our own, clocking in at 99% of Earth’s diameter. The research team is led by Kevin Stevenson and Jacob Lustig-Yaeger, both of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
The team chose to observe this target with Webb after carefully reviewing targets of interest from NASA’s Transiting Exoplanet Survey Satellite (TESS), which hinted at the planet’s existence. Webb’s Near-Infrared Spectrograph(NIRSpec) captured the planet easily and clearly with only two transit observations. “There is no question that the planet is there. Webb’s pristine data validate it,” said Lustig-Yaeger. “The fact that it is also a small, rocky planet is impressive for the observatory,” Stevenson added.
“These first observational results from an Earth-size, rocky planet open the door to many future possibilities for studying rocky planet atmospheres with Webb,” agreed Mark Clampin, Astrophysics Division director at NASA Headquarters in Washington. “Webb is bringing us closer and closer to a new understanding of Earth-like worlds outside our solar system, and the mission is only just getting started.”
Among all operating telescopes, only Webb is capable of characterizing the atmospheres of Earth-sized exoplanets. The team attempted to assess what is in the planet’s atmosphere by analyzing its transmission spectrum. Although the data shows that this is an Earth-sized terrestrial planet, they do not yet know if it has an atmosphere. “The observatory’s data are beautiful,” said Erin May, also of the Johns Hopkins University Applied Physics Laboratory. “The telescope is so sensitive that it can easily detect a range of molecules, but we can’t yet make any definitive conclusions about the planet’s atmosphere.”
Although the team can’t conclude what is present, they can definitely say what is not present. “There are some terrestrial-type atmospheres that we can rule out,” explained Lustig-Yaeger. “It can’t have a thick methane-dominated atmosphere, similar to that of Saturn’s moon Titan.”
The team also notes that while it’s possible the planet has no atmosphere, there are some atmospheric compositions that have not been ruled out, such as a pure carbon dioxide atmosphere. “Counterintuitively, a 100% carbon dioxide atmosphere is so much more compact that it becomes very challenging to detect,” said Lustig-Yaeger. Even more precise measurements are required for the team to distinguish a pure carbon dioxide atmosphere from no atmosphere at all. The researchers are scheduled to obtain additional spectra with upcoming observations this summer.
Webb also revealed that the planet is a few hundred degrees warmer than Earth, so if clouds are detected, it may lead the researchers to conclude that the planet is more like Venus, which has a carbon dioxide atmosphere and is perpetually shrouded in thick clouds. “We’re at the forefront of studying small, rocky exoplanets,” Lustig-Yaeger said. “We have barely begun scratching the surface of what their atmospheres might be like.”
The researchers also confirmed that the planet completes an orbit in just two days, information that was almost instantaneously revealed by Webb’s precise light curve. Although LHS 475 b is closer to its star than any planet in our solar system, its red dwarf star is less than half the temperature of the Sun, so the researchers project it still could have an atmosphere.
The researchers’ findings have opened the possibilities of pinpointing Earth-sized planets orbiting smaller red dwarf stars. “This rocky planet confirmation highlights the precision of the mission’s instruments,” Stevenson said. “And it is only the first of many discoveries that it will make.” Lustig-Yaeger agreed. “With this telescope, rocky exoplanets are the new frontier.”
LHS 475 b is relatively close, at only 41 light-years away, in the constellation Octans.
The team’s results were presented at a press conference of the American Astronomical Society (AAS) on Wednesday, Jan. 11, 2023.
Galaxies in early universe were surprisingly diverse, James Webb Space Telescope finds
Even early on, 'galaxies were already fairly evolved and had a wide range of structures.'
(Image credit: NASA/STScI/CEERS/TACC/S. Finkelstein/M. Bagley/Z. Levay; Cutout images: NASA/STScI/CEERS/TACC/S. Finkelstein/M. Bagley/J. Kartaltepe)
The James Webb Space Telescope is changing our understanding of the cosmos.
Galaxies in the early days of the universe were much more varied and mature than previously thought, according to a new study of observations of hundreds of galaxies by NASA's James Webb Space Telescope (JWST).
The Cosmic Evolution Early Release Science (CEERS) Survey has been using JWST to look far back in time, studying galaxies as they were around 11 to 13 billion years ago.
The images of faint, highly redshifted galaxies returned by JWST are much sharper than similar photos captured by the Hubble Space Telescope. These new images have revealed the presence of mature features such as disks and spheroidal components, Jeyhan Kartaltepe, an associate professor in the Rochester Institute of Technology's School of Physics and Astronomy, said in a statement(opens in new tab).
"This means that, even at these high redshifts, galaxies were already fairly evolved and had a wide range of structures," said Kartaltepe, lead author of the new paper and a CEERS co-investigator.
These early galaxies were therefore much more like the galaxies of the present than previously known.
"This tells us that we don't yet know when the earliest galaxy structures formed," said Kartaltepe. "We're not yet seeing the very first galaxies with disks. We'll have to examine a lot more galaxies at even higher redshifts to really quantify at what point in time features like disks were able to form."
The results of the study, which used an early JWST data set from June last year, have been accepted for publication in The Astrophysical Journal and posted on the online preprint site ArXiv(opens in new tab).
Since then, the CEERS survey has racked up another 60 observing hours with JWST, meaning there may be many thousands of high redshift galaxies to further explore and advance our understanding of how the early universe evolved.
JWST Heralds a New Dawn for Exoplanet Science
The James Webb Space Telescope is opening an exciting new chapter in the study of exoplanets and the search for life beyond Earth
Any future historian of 21st-century space science may well divide the subject into two eras: before the James Webb Space Telescope (JWST) and after. The telescope was built to transform our understanding of the cosmos by studying the first stars and galaxies, and within less than a year of operations, it has already delivered tantalizing and potentially revolutionary results from its observations of the early universe. Yet JWST’s work is poised to transform many other subfields of astronomy, none arguably more so than the study of exoplanets, worlds orbiting other stars. Astronomers now know of more than 5,000 exoplanets but know next to nothing about most of them—their composition, environmental conditions or even prospects for life. JWST is beginning to change that, thanks to its as-yet-unparalleled ability to directly observe these alien worlds, picking apart their light to discern finer details and occasionally even managing to snap an exoplanet’s picture against the overwhelming glare of its home star.
Such results remain a far cry from the astrobiological holy grail of finding and studying potentially Earth-like worlds but are enormously exciting nonetheless, given that JWST and its core science goals were conceived before exoplanets were even known to exist. “The exoplanet community is just giddy at the moment,” says Mark Clampin, director of the Astrophysics Division at NASA Headquarters in Washington, D.C.
JWST’s first year of science is scheduled from July 2022 through June 2023. Of that period, called Cycle 1, about a quarter of the telescope’s time is being devoted to exoplanets across about 75 programs. One of the most exciting applications of JWST is studying exoplanet atmospheres. Gold-plated and about as wide as a full-grown African elephant, the telescope’s infrared-tuned primary mirror allows it to probe the atmospheres of exoplanets to a degree never before possible. “With the Hubble [Space Telescope], we’ve done a decade of detecting water, which we found abundantly, but not much else,” says Nikole Lewis of Cornell University. “That was the only thing you could measure.” JWST can see water, too—as well as a much wider array of molecules including carbon dioxide, sodium, and more. Some of the compounds JWST can detect, such as methane, are closely associated with metabolic processes in Earth’s biosphere, making them possible biosignatures that could help reveal life’s presence on other potentially habitable worlds beyond the solar system.
In August astronomers revealed they had used JWST to detect carbon dioxide on an exoplanet for the first time by watching for signs of the gas in the light of a gas giant planet’s host star filtering through the world’s atmosphere. Known as transmission spectroscopy, this technique is incredibly useful not only for studying giant planets but also for investigating smaller ones that might be more like our solar system’s retinue of rocky worlds. “We needed to start with ‘Okay, do they have air?’” Lewis says. “Once we understand that, we can develop a better strategy of looking for biosignature gases.”
At the 241st meeting of the American Astronomical Society (AAS) in Seattle earlier this month, astronomers announced another transmission spectroscopy result from JWST. This time the telescope studied an Earth-sized world called LHS 475 b, which orbits a red dwarf star 41 light-years away from Earth. In this case, JWST actually confirmed the planet’s existence, which previously had been hinted at by NASA’s Transiting Exoplanet Survey Satellite (TESS). “We confirmed it was a planet by observing it with JWST,” says Sarah Moran of the University of Arizona, a collaborator on the result.
JWST observed two orbits of the planet around its star, but an additional observation expected in May will be needed to better parse the contents of the planet’s atmosphere. So far, however, the team “can say a lot of things about what the atmosphere is not like,” Moran says. “We know it’s not hydrogen dominated like Jupiter or Saturn. We think it probably does not have an Earth-like atmosphere. But it could have a carbon dioxide atmosphere like Venus or Mars, or it could have no atmosphere at all like Mercury.” Those results could help inform the study of other rocky planets around red dwarfs, which account for some three quarters of all stars in the Milky Way. “We’re in the very first stages of trying to measure atmospheres for rocky planets and trying to figure out if a planet can be habitable,” Moran says.
In terms of studying rocky planets, JWST is largely limited to worlds that orbit red dwarfs, which are dim enough to avoid overloading the telescope’s exquisitely sensitive optics. Such stars are known to be prone to intense flaring that could blast away the atmospheres of worlds like LHS 475 b, which orbit perilously close to their host stars in comparison with the much wider star-planet separations among our solar system’s rocky worlds. “There’s the possibility that absolutely all of their atmospheres have been blown away by their stars,” Lewis says. One major red dwarf target of interest, the TRAPPIST-1 system nearly 40 light-years from Earth, contains seven Earth-sized worlds. Several of these are in the star’s habitable zone—the region around the star in which sufficient planet-warming starlight might allow liquid water to exist. Early observations of TRAPPIST-1 are still underway, including ones seeking out atmospheres. Those results could go a long way toward revealing whether red dwarf worlds can actually be habitable. “Hopefully we’ll know by the end of Cycle 1,” Lewis says.
JWST also sports an exciting add-on called a coronagraph, a device for blocking most of the light of stars so that fainter accompanying planets can be seen (this was crucial for JWST’s first-ever exoplanet image, which researchers unveiled last September). The starlight-suppressing power of the telescope’s coronagraph is insufficient for revealing any small, potentially habitable worlds, but recent work has shown the coronagraph should allow JWST to see worlds down to the size of Jupiter or Saturn that are orbiting red dwarf stars at or beyond five times the Earth-sun distance (five astronomical units, or AU). That’s roughly the position of Jupiter in our own solar system.
This analysis comes from Kellen Lawson of NASA’s Goddard Space Flight Center and his colleagues, who at the recent AAS meeting debuted stunning infrared views of a sprawling debris disk encircling a young star some 32 light-years from Earth. “In the past, direct imaging has been limited to 10 or so Jupiter masses,” Lawson says. “Here we’re sensitive to a [single] Jupiter mass.” That will allow JWST to look for rough analogues of Jupiter around other stars in a way not possible before. “Our hope is, with JWST, we can constrain the presence of planets in this regime,” Lawson says. Such directly imaged planets can be directly pinpointed in their orbits around their stars, giving a prime opportunity “to follow-up and get a ton of really incredible data.”
Astronomers are also excited about the exoplanet capabilities of another telescope, the European Space Agency’s (ESA’s) Gaia observatory. Launched to space in 2013 primarily to map the motions and positions of billions of stars in our galaxy, the telescope is also expected to find thousands of exoplanets. At the AAS meeting, Sasha Hinkley of the University of Exeter in England—who leads one of JWST’s early exoplanet imaging programs—announced that, using Gaia and the Very Large Telescope (VLT) in Chile, his team had seen an unusual planet some 130 light-years from Earth that appeared to be undergoing nuclear fusion. “It’s burning deuterium,” he says, referring to a hydrogen isotope that achieves starlight-powering nuclear fusion at lower temperatures than normal hydrogen. Further studies of the system, Hinkley says, could help astronomers draw less blurry lines among stars, planets and brown dwarfs—the latter being a loosely defined class of objects that fall between planets and stars in mass. The 130-light-year-distant planet, spotted thanks to Gaia witnessing a wobble in its host star’s motion caused by the unseen world’s gravitational pull, could be one of many upcoming exoplanets found by the telescope, some of which could also be interesting targets for JWST.
The quest for Earthlike worlds, however, seems set to define JWST’s exoplanet legacy despite being largely beyond the telescope’s reach. “That’s where all this work is headed,” Hinkley says, “and that’s why a majority of people are in this game.” In 2026 a new ESA mission called PLATO will launch, with finding such worlds as its primary goal. PLATO will stare at vast swathes of the sky to, for the first time, hunt in earnest for Earth-like worlds around sunlike stars within about 1,000 light-years of the solar system. A few tens of such planets are expected to be found during the telescope’s four-year primary mission, says Ana Heras of ESA, the mission’s project scientist. “We really don’t know what the occurrence rate is [for Earth-like planets],” she says. PLATO will go some way to telling us how many, if any, there are in our corner of the galaxy.
JWST will not be able to closely study such worlds. Nor will its successor, the Nancy Grace Roman Space Telescope, set to launch by 2027, be capable of doing so. But Roman will play a crucial role alongside its other scientific objectives: testing the advanced coronagraph technology that will be needed to produce images of potentially habitable Earth-like worlds around stars like our sun. That technology is meant to then be employed on JWST and Roman’s successor, the newly dubbed Habitable Worlds Observatory, which is set to launch no sooner than the late 2030s on a mission to produce the first-ever images of potentially habitable Earths. That telescope must be “about 100 times more stable” in space than JWST to achieve such a goal, says Bruce Macintosh, director of the University of California Observatories. “That’s not a negligible challenge.”
The road to this eventuality is a long one. “We’re at the beginning of a journey here,” Clampin says. But even leaving aside any talk of holy grails, JWST’s transformative early exoplanet results remain a thrill for scientists. The best, however, is still yet to come. “People need to be patient,” Lewis says. “The first cycle is all about picking the low-hanging fruit. We’re going to start going crazy in the next few cycles.”
Quelle: SCIENTIFIC AMERICAN