James Webb Space Telescope 'fingerprints' earliest galaxies
It's not much to look at - just a little red blob with the rather quirky name of JADES-GS-z13-0.
But this faint smudge, imaged by the James Webb Space Telescope, is the "most distant galaxy" so far confirmed by gold-standard measurement.
We're looking at this collection of stars as it was a mere 325 million years after the Big Bang.
Put another way - if the Universe is 13.8 billion years old, it means we're observing JADES-GS-z13-0 when the cosmos was only 2% of its current age.
The light from this blob has been travelling towards us for a very, very long time.
"I'm actually in awe and incredibly grateful to be part of this moment," said Dr Emma Curtis-Lake, who is part of the international team that published details of the discovery on Friday.
The significance is not lost on the University of Hertfordshire, UK, astronomer.
Our previous "most distant galaxy" was detected by Webb's predecessor telescope, the veteran Hubble space observatory. It spied the equally quirkily named GN-z11. This galaxy was seen to be a little closer to us, at a time when the Universe was only 400 million years old.
But the big deal here is that the baton has truly now been passed from Hubble to James Webb, from one great telescope to the next great telescope, as scientists seek to trace the earliest epoch of star formation.
Indeed, the US space agency Nasa's recently launched Webb observatory has been given the primary objective of finding the very first stars to light up the cosmos.
JADES-GS-z13-0 isn't quite from that time, but we're getting very close to it.
This is where a hand goes up to ask: But weren't there reports over the Summer of Webb observations that are even more distant than JADES-GS-z13-0?
The answer is - "maybe", and the uncertainty rests on the difference between the techniques used to make a distance determination.
Astronomers will use the term "redshift" to describe distances.
It's essentially a measure of how the light coming from a far-off galaxy has been stretched to longer wavelengths by the expansion of the Universe.
The greater the distance, the greater the stretching - giving a higher redshift number (the JADES galaxy has a redshift of 13.2; the clue's in the name).
Scientists can get reasonably good estimates by studying, in broad terms, the brightness and colour of their targets using a few, specific filters on their camera. This technique is called photometry.
Distinctive big jumps or "breaks" in the spectrum of a galaxy can make it brighter and darker in the various filters and give an indication of its distance.
It's only a guide, however, and isn't always reliable.
If there's a lot of dust in a galaxy, it can make the object look redder and a lot further away than it really is.
To get the best measure, astronomers prefer to use spectroscopy, a more detailed technique in which the light signal is split up into its component wavelengths.
This allows them to get a better handle on where the "breaks" are in the galaxy spectrum and also to see emission lines from elements such as hydrogen, oxygen, and neon.
Comparing their measured wavelengths with those known from lab experiments gives a direct indication of how much the light has been stretched and thus the redshift and distance.
Both JADES-GS-z13-0 and GN-z11 have been confirmed through spectroscopy, the gold-standard approach. The higher redshift numbers you may have seen reported in recent months are all based on photometry.
This is difficult work all round. The targets appear extremely faint even to Webb and its giant, 6.5m-wide mirror.
Dr Curtis-Lake and her JADES (JWST Advanced Deep Extragalactic Survey) colleagues spent hours collecting a mosaic of images in an old Hubble field of view.
"It's an incredibly small patch of sky - equivalent to viewing the eye of the Queen on a pound coin held at arm's length," said Dr Renske Smit from Liverpool John Moores University. "But within that patch, Webb sees 10s of thousands of galaxies."
IMAGE SOURCE, NASA, ESA, CSA, M. ZAMANI, JADES COLLABORATION
Image caption,
The JADES field repeats old Hubble observations but goes much, much deeper
The new space telescope carries an incredibly powerful near-infrared spectrometer (NIRSpec) provided by the European Space Agency. It's NIRSpec's job to do the detailed analysis of the faint light signals.
It uses a remarkable shutter array - a collection of 250,000 tiny doors, each only a few human hairs in width - to select the objects for study.
Within the "Queen's eye", the team chose 250 promising candidates, four of which turned out to be at stupendous distances.
JADES-GS-z13-0 was the furthest away, but JADES-GS-z12-0, JADES-GS-z11-0 and JADES-GS-z10-0 weren't that far short.
IMAGE SOURCE, AIRBUS
Image caption,
NIRSpec was a major European contribution to the James Webb project
"This is what JWST was built to do and the European-built NIRSpec instrument lies at the heart of it," commented Prof Mark McCaughrean, Esa's senior scientific advisor.
"The search for 'first light' in the Universe needs a large, cold space telescope and a sensitive infrared camera to identify things that might be faint galaxies forming just a few hundred million years after the Big Bang.
"But there's a lot of hay and not many needles, so you have to look at many candidates, smearing out the tiny amount of light from each one into a spectrum and using tell-tale tracers to see if they have the right distance and age. By being able to efficiently examine hundreds of targets at a time, NIRSpec brings a kind of cosmic magnet to the haystack," he told BBC News.
Quelle: BBC
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Update: 17.12.2022
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JWST gets first glimpse of 7-planet system with potentially habitable worlds
Astronomers have been eager for the landmark telescope to study the TRAPPIST-1 system.
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.
Prized planets
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.”
Quelle: nature
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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 here.)
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.
Quelle: Sky&Telescope
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Update: 23.12.2022
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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 James Webb Space Telescopehas just produced one of the most detailed photos of the wreath-shaped galaxyever seen.
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 black hole. 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.
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.
