The TRAPPIST-1 system, shown in this rendering, includes seven Earth-sized planets circling a single, relatively cool star. Credit: NASA/JPL-Caltech
The James Webb Space Telescope (JWST) has had its first look at a hotly anticipated set of targets — the atmospheres of some of the seven Earth-sized planets circling the star TRAPPIST-1, just 12 parsecs (39 light years) from Earth. All seven lie in or near their star’s habitable zone, where liquid water could exist, and astronomers consider them the best known laboratory for studying what might make planets beyond the Solar System suitable for life.
Results so far are preliminary and don’t yet indicate what sorts of atmospheres these planets might actually have. But if they have dense atmospheres containing intriguing molecules such as carbon dioxide or methane, the US$10-billion telescope will be able to detect them in the coming months and years. No other observatory has been powerful enough to spot these atmospheres.
“We’re in business,” said Björn Benneke, an astronomer at the University of Montreal in Canada, during a symposium on first results from JWST in Baltimore, Maryland, on 13 December.
The TRAPPIST-1 planetary system,
mapped out in 2017, offers astronomers multiple chances of understanding the formation and evolution of Earth-sized worlds orbiting a single star. The star is relatively faint and cool, and the seven planets are nestled closer to it than Mercury is to the Sun.
JWST is observing all of the planets in its first year of science operations,
which began in June. Many of those observations have already been made, but none had been shown publicly until this week’s symposium, which took place at the Space Telescope Science Institute, the JWST operations centre.
All of the planets in the TRAPPIST-1 system are closer to their star than Mercury is to the Sun.Credit: NASA/JPL-Caltech
The TRAPPIST-1 planets are designated b to h, with b being closest to the star and h farthest.
Benneke presented the first JWST studies of TRAPPIST-1g. So far, the telescope has been able to make out that the planet probably doesn’t have a hydrogen-rich atmosphere — something the Hubble Space Telescope had previously shown. Such an atmosphere would be physically large owing to its low density, so it would be relatively easy to spot. That could mean that the planet has a denser atmosphere, made of heavier molecules such as carbon dioxide, or no atmosphere at all.
JWST studies planetary atmospheres mainly by watching how they filter starlight as the planets pass in front of the star: particular molecules absorb the starlight in characteristic ways. Which molecules make up the atmosphere can indicate how a planet evolved and whether it might have life on its surface. It will take more observations and analysis time for researchers to discover whether TRAPPIST-1g has an atmosphere and, if so, what it is made of.
Constructing a ‘family portrait’
The TRAPPIST-1 data are much harder to analyse than those gathered from larger exoplanets, including WASP-39b, a planet closer to the size of Jupiter
that JWST has studied in detail. TRAPPIST-1’s planets are much smaller, and the signal from their atmospheres is more difficult to tease out. Magnetic disturbances in the star can also induce signals that confound interpretations of the data.
“We needed this first look to know what we’re dealing with,” says Knicole Colón, an astronomer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Benneke declined to speak to reporters about the TRAPPIST-1g results, saying that he is working on a paper for a scientific journal.
In a poster presentation at the conference, Olivia Lim, an astronomer at the University of Montreal, described two JWST observations of the innermost planet in the system, TRAPPIST-1b. Her team, too, has been unable to tease out a signal indicating the composition of the planet’s atmosphere. But preliminary studies suggest that, like planet 1g, it probably doesn’t have a puffy, hydrogen-rich atmosphere.
Lim’s team has several observations of other TRAPPIST-1 planets already in hand, including one set of results gathered last week that she hasn’t had time to look at in the crush of JWST results. “It’s hectic,” she says.
But more results on the extraordinary planetary system are on the way, Colón says: “Within the next year, we’ll have a family portrait.”
WEBB'S GALACTIC DISTANCE RECORD IS NOW OFFICIAL
Spectroscopic measurements confirm Webb’s distance record, with images revealing galaxies that existed just 330 million years after the Big Bang.
This image taken by the James Webb Space Telescope highlights the region of study by the JWST Advanced Deep Extragalactic Survey (JADES). This area is in and around the Hubble Space Telescope’s Ultra Deep Field.
Image credit: NASA / ESA / CSA / M. Zamani (ESA / Webb); Science: B. Robertson (UCSC) / S. Tacchella (Cambridge) / E. Curtis-Lake (Hertfordshire) / S. Carniani (Scuola Normale Superiore) / JADES Collaboration.
Astronomers using the James Webb Space Telescope (JWST) have confirmed the most distant galaxies ever observed. Some formed just 330 million years after the Big Bang, when the universe was a mere 2% of its current age.
These new results, based on highly detailed spectroscopic measurements, provide concrete distances to galaxies revealed in Webb observations back in August. “It was crucial to prove that these galaxies do, indeed, inhabit the early universe,” says Emma Curtis-Lake (University of Hertfordshire, UK). “It’s very possible for closer galaxies to masquerade as very distant galaxies.”
Curtis-Lake is part of a group of 80 astronomers from 10 countries behind the JWST Advanced Deep Extragalactic Survey (JADES). They've been given a total of a month's observing time, spread over two years, to look at the spectra of distant galaxies. The first part of this effort saw them observe an area of the night sky in and around the famous Hubble Ultra Deep Field (HUDF). (The team is in the process of publishing this data; although the study has not yet passed peer review, NASA has made it available
Spectra of distant galaxies have a distinct cut-off point called the
Lyman break, caused by intergalactic hydrogen absorbing wavelengths shorter than 91.2 nanometers on its journey towards Earth. Yet the ongoing expansion of the universe stretches the wavelength of light from these galaxies in the early universe, which in turn shifts their Lyman break to longer wavelengths, too. The longer the wavelength at which a galaxy appears to drop off in brightness, the older and more distant it is.
The Lyman break can be seen in broadband images at multiple wavelengths, which is how astronomers first pinpointed these galaxies in August. However, galaxies may appear to “drop out” at shorter wavelengths for other reasons, such as veils of dust created by bursts of star formation. Spectroscopic measurements fill in the gaps, providing additional data that can confirm that a drop in brightness is indeed due to the galaxies’ extreme distance.
The JADES team collected 28 hours of data on 250 different galaxies using Webb's Near Infrared Spectrograph (NIRSpec) instrument. They hit the jackpot with four of them. The location of their Lyman breaks suggest that they are all beyond redshift 10. Two of them have a redshift of 13, meaning they formed as early as 330 million years after the Big Bang.
Using Webb’s NIRCam instrument, scientists observed the field in nine different infrared wavelength ranges. From these images (shown at left), the team searched for faint galaxies that are visible in the infrared but whose spectra abruptly cut off at a critical wavelength known as the Lyman break. Webb’s NIRSpec instrument then yielded a precise measurement of each galaxy’s redshift (shown at right).
Image credit: NASA / ESA / CSA / STScI / M. Zamani (ESA/Webb) / L. Hustak (STScI); Science: B. Robertson (UCSC) / S. Tacchella (Cambridge) / E. Curtis-Lake (Hertfordshire) / S. Carniani (Scuola Normale Superiore) / JADES Collaboration.
These ancient galaxies form part of a newly released image of the HUDF area taken with Webb's Near Infrared Camera (NIRCam) using nine different wavelengths of infrared light. Blue in the image represents light at 1.15 microns, green is 2.0 microns, and red is 4.44 microns.
“To find these early galaxies in such stunningly beautiful images is a special experience,” says team member Brant Robertson (University of California, Santa Cruz).
Studying these distant galaxies is a crucial part of working out how we arrived at the universe we see today. “It is hard to understand galaxies without understanding the initial periods of their development,” says team member Sandro Tacchella (University of Cambridge, UK). “As with humans, so much of what happens later depends on the impact of these early generations of stars. So many questions about galaxies have been waiting for the transformative opportunity of Webb, and we're thrilled to be able to play a part in revealing this story.”
Michael Strauss (Princeton University), who was not involved in the research, is excited to see the results. “It is completely amazing that we are measuring spectroscopic redshifts for galaxies at redshift of 13, looking back to the first few hundred million years of the universe’s history,” he says. “We’re just starting to probe what is often called the ‘Cosmic Dawn’ with these observations, and who knows what the next year — much less the next 20 years — with JWST will teach us.”
If this is the appetizer, we may not have to wait long for the next course. JADES will continue in 2023 with a detailed study of the Hubble Deep Field, before returning to the Ultra Deep Field for another round of imaging and spectroscopy. These new distance records could easily be broken as astronomers probe further and further into the universe's youth.
James Webb Space Telescope spots mesmerizing wreath-like galaxy
Check out that glowing active galactic nucleus.
Some 220 million light-years away, nestled in the constellation Pegasus, spiral galaxy NGC 7469 whirls around an active galactic nucleus (AGN). It's one of the more well-studied galaxies in our universe, but the
has just produced one of the most detailed photos of the wreath-shaped James Webb Space Telescope ever seen. galaxy
Because NGC 7469 faces us head-on, astronomers can observe its entire 90,000-light-year span. Of particular interest is its AGN, the bright region at its center where dust and gas light up as they're consumed by the galaxy's supermassive
. The structure isn't uncommon, but what is unusual is that NGC 7469 has a starburst ring just 1,500 light-years from the AGN — an exceptionally close distance. black hole
Since there is so much material packed into a relatively small area, it's been difficult for scientists to peer into the AGN and its surrounding starburst. But that has now changed with Webb's ultra-sensitive infrared imaging instruments.
This image has captured new details within NGC 7469's AGN, including "very young star-forming clusters never seen before, as well as pockets of very warm, turbulent molecular gas, and direct evidence for the destruction of small dust grains within a few hundred light-years of the nucleus," according to
a statement (opens in new tab)from the European Space Agency (ESA), a partner on the observatory.
In this image, Webb has also captured ionized atomic gas emissions from the nucleus that are traveling at some 4 million mph (6.4 million kph). While scientists already knew about the galactic outflow, this image marks the first time they were able to see it in such crisp detail.
And, by the way, that six-pointed starburst that appears to emanate from the center of the galaxy? That doesn't technically exist. It's what scientists call an imaging artifact, and more specifically, a diffraction spike — a pattern that's created on the image when light bends around the edges of telescopes. Webb images are characterized by their six-pointed diffraction spikes, a signature of the observatory's hexagonal mirror.
Scientists hope to use images like these to study the relationship between AGNs and starburst activity.