The James Webb Space Telescope resumed science operations Dec. 20, after Webb’s instruments intermittently went into safe mode beginning Dec. 7 due to a software fault triggered in the attitude control system, which controls the pointing of the observatory. During a safe mode, the observatory’s nonessential systems are automatically turned off, placing it in a protected state until the problem can be fixed. This event resulted in several pauses to science operations totaling a few days over that time period. Science proceeded otherwise during that time. The Webb team adjusted the commanding system, and science has now fully resumed.
The observatory and instruments are all in good health, and were not in any danger while Webb’s onboard fault management system worked as expected to keep the hardware safe. The team is working to reschedule the affected observations.
NASA’s James Webb Space Telescope has captured one of the first medium-deep wide-field images of the cosmos, featuring a region of the sky known as the North Ecliptic Pole. The image, which accompanies a paper published in the Astronomical Journal, is from the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) GTO program.
“Medium-deep” refers to the faintest objects that can be seen in this image, which are about 29th magnitude (1 billion times fainter than what can be seen with the unaided eye), while “wide-field” refers to the total area that will be covered by the program, about one-twelfth the area of the full moon. The image is comprised of eight different colors of near-infrared light captured by Webb’s Near-Infrared Camera (NIRCam), augmented with three colors of ultraviolet and visible light from the Hubble Space Telescope. This beautiful color image unveils in unprecedented detail and to exquisite depth a universe full of galaxies to the furthest reaches, many of which were previously unseen by Hubble or the largest ground-based telescopes, as well as an assortment of stars within our own Milky Way galaxy. The NIRCam observations will be combined with spectra obtained with Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS), allowing the team to search for faint objects with spectral emission lines, which can be used to estimate their distances more accurately.
We asked members of the PEARLS team that created this image to share their thoughts and reactions while analyzing this field:
“For over two decades, I’ve worked with a large international team of scientists to prepare our Webb science program,” said Rogier Windhorst, Regents Professor at Arizona State University (ASU) and PEARLS principal investigator. “Webb’s images are truly phenomenal, really beyond my wildest dreams. They allow me to measure the number density of galaxies shining to very faint infrared limits and the total amount of light they produce.”
“I was blown away by the first PEARLS images,” agreed Rolf Jansen, Research Scientist at ASU and a PEARLS co-investigator. “Little did I know, when I selected this field near the North Ecliptic Pole, that it would yield such a treasure trove of distant galaxies, and that we would get direct clues about the processes by which galaxies assemble and grow. I can see streams, tails, shells, and halos of stars in their outskirts, the leftovers of their building blocks.”
“The Webb images far exceed what we expected from my simulations in the months prior to the first science observations,” said Jake Summers, a research assistant at ASU. “Looking at them, I was most surprised by the exquisite resolution. There are many objects that I never thought we would actually be able to see, including individual globular clusters around distant elliptical galaxies, knots of star formation within spiral galaxies, and thousands of faint galaxies in the background.”
“The diffuse light that I measured in front of and behind stars and galaxies has cosmological significance, encoding the history of the universe,” said Rosalia O’Brien, a graduate research assistant at ASU. “I feel very lucky to start my career right now. Webb’s data is like nothing we have ever seen, and I’m really excited about the opportunities and challenges it offers.”
“I spent many years designing the tools to find and accurately measure the brightnesses of all objects in the new Webb PEARLS images, and to separate foreground stars from distant galaxies,” says Seth Cohen, a research scientist at ASU and a PEARLS co-investigator. “The telescope’s performance, especially at the shortest near-infrared wavelengths, has exceeded all my expectations, and allowed for unplanned discoveries.”
“The stunning image quality of Webb is truly out of this world,” agreed Anton Koekemoer, research astronomer at STScI, who assembled the PEARLS images into very large mosaics. “To catch a glimpse of very rare galaxies at the dawn of cosmic time, we need deep imaging over a large area, which this PEARLS field provides.”
“I hope that this field will be monitored throughout the Webb mission, to reveal objects that move, vary in brightness, or briefly flare up,” said Rolf. Added Anton: “Such monitoring will enable the discovery of time-variable objects like distant exploding supernovae and bright accretion gas around black holes in active galaxies, which should be detectable to larger distances than ever before.”
“This unique field is designed to be observable with Webb 365 days per year, so its time-domain legacy, area covered, and depth reached can only get better with time,” concluded Rogier.
About the Authors
Rogier Windhorst is a Regents Professor in the School of Earth and Space Exploration (SESE) of the Arizona State University (ASU). He serves as one of six Webb Interdisciplinary Scientists worldwide, and is the principal investigator of the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) program (program IDs 1176, 2738). The PEARLS team consists of nearly 100 scientists spread across 18 time zones world-wide.
Rolf Jansen is a research scientist at ASU/SESE and PEARLS co-investigator. He selected the Webb North Ecliptic Pole Time Domain Field and led its development as a new community field for time-domain science with Webb, including the design of the NIRCam observations. He also is principal investigator of the Hubble images used in this color composite.
Seth Cohen is a research scientist at ASU/SESE and a PEARLS co-investigator. He led software development and photometric calibration, and generated object catalogs for this field.
Jake Summers is a research assistant at ASU/SESE, responsible for processing, organizing, and distributing the PEARLS data to the team, including the generation of initial mosaics and color composites.
Rosalia O’Brien is a graduate research assistant at ASU/SESE, responsible for measuring diffuse light, and for reprocessing the Hubble images.
Anton Koekemoer is a research astronomer at STScI, responsible for the astrometric alignment and combination of individual NIRCam detector images into the final PEARLS mosaics.
Aaron Robotham is a professor at the University of Western Australia’s ICRAR, and was responsible for the detector-level post-processing of the NIRCam data.
Christopher Willmer is a research astronomer at the University of Arizona’s Steward Observatory. A member of the NIRCam team, he helped develop the Webb North Ecliptic Pole Time Domain Field, and constructed camera artifacts templates.
Editor’s Note: This post highlights data from Webb science in progress, which has not yet been through the peer-review process.
An international team of astronomers has used data from NASA’s James Webb Space Telescope to report the discovery of the earliest galaxies confirmed to date. The light from these galaxies has taken more than 13.4 billion years to reach us, as these galaxies date back to less than 400 million years after the big bang, when the universe was only 2% of its current age.
Earlier data from Webb had provided candidates for such infant galaxies. Now, these targets have been confirmed by obtaining spectroscopic observations, revealing characteristic and distinctive patterns in the fingerprints of light coming from these incredibly faint galaxies.
“It was crucial to prove that these galaxies do, indeed, inhabit the early universe. It’s very possible for closer galaxies to masquerade as very distant galaxies,” said astronomer and co-author Emma Curtis-Lake from the University of Hertfordshire in the United Kingdom. “Seeing the spectrum revealed as we hoped, confirming these galaxies as being at the true edge of our view, some further away than Hubble could see! It is a tremendously exciting achievement for the mission.”
The observations resulted from a collaboration of scientists who led the development of two of the instruments on board Webb, the Near-Infrared Camera (NIRCam) and the Near-Infrared Spectrograph (NIRSpec). The investigation of the faintest and earliest galaxies was the leading motivation behind the concepts for these instruments. In 2015 the instrument teams joined together to propose the JWST Advanced Deep Extragalactic Survey (JADES), an ambitious program that has been allocated just over one month of the telescope’s time spread over two years, and is designed to provide a view of the early universe unprecedented in both depth and detail. JADES is an international collaboration of more than eighty astronomers from ten countries. “These results are the culmination of why the NIRCam and NIRSpec teams joined together to execute this observing program,” shared co-author Marcia Rieke, NIRCam principal investigator, of the University of Arizona in Tucson.
The first round of JADES observations focused on the area in and around the Hubble Space Telescope’s Ultra Deep Field. For over 20 years, this small patch of sky has been the target of nearly all large telescopes, building an exceptionally sensitive data set spanning the full electromagnetic spectrum. Now Webb is adding its unique view, providing the faintest and sharpest images yet obtained.
The JADES program began with NIRCam, using over 10 days of mission time to observe the field in nine different infrared colors, and producing exquisite images of the sky. The region is 15 times larger than the deepest infrared images produced by the Hubble Space Telescope, yet is even deeper and sharper at these wavelengths. The image is only the size a human appears when viewed from a mile away. However, it teems with nearly 100,000 galaxies, each caught at some moment in their history, billions of years in the past.
“For the first time, we have discovered galaxies only 350 million years after the big bang, and we can be absolutely confident of their fantastic distances,” shared co-author Brant Robertson from the University of California Santa Cruz, a member of the NIRCam science team. “To find these early galaxies in such stunningly beautiful images is a special experience.”
From these images, the galaxies in the early universe can be distinguished by a tell-tale aspect of their multi-wavelength colors. Light is stretched in wavelength as the universe expands, and the light from these youngest galaxies has been stretched by a factor of up to 14. Astronomers search for faint galaxies that are visible in the infrared but whose light abruptly cuts off at a critical wavelength. The location of the cutoff within each galaxy’s spectrum is shifted by the universe’s expansion. The JADES team scoured the Webb images looking for these distinctive candidates.
They then used the NIRSpec instrument, for a single observation period spanning three days totaling 28 hours of data collection. The team collected the light from 250 faint galaxies, allowing astronomers to study the patterns imprinted on the spectrum by the atoms in each galaxy. This yielded a precise measurement of each galaxy’s redshift and revealed the properties of the gas and stars in these galaxies.
“These are by far the faintest infrared spectra ever taken,” said astronomer and co-author Stefano Carniani from Scuola Normale Superiore in Italy. “They reveal what we hoped to see: a precise measurement of the cutoff wavelength of light due to the scattering of intergalactic hydrogen.”
Four of the galaxies studied are particularly special, as they were revealed to be at an unprecedentedly early epoch. The results provided spectroscopic confirmation that these four galaxies lie at redshifts above 10, including two at redshift 13. This corresponds to a time when the universe was approximately 330 million years old, setting a new frontier in the search for far-flung galaxies. These galaxies are extremely faint because of their great distance from us. Astronomers can now explore their properties, thanks to Webb’s exquisite sensitivity.
Astronomer and co-author Sandro Tacchella from the University of Cambridge in the United Kingdom explained, “It is hard to understand galaxies without understanding the initial periods of their development. Much 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.”
JADES will continue in 2023 with a detailed study of another field, this one centered on the iconic Hubble Deep Field, and then return to the Ultra Deep Field for another round of deep imaging and spectroscopy. Many more candidates in the field await spectroscopic investigation, with hundreds of hours of additional time already approved.
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).
Editor’s Note: This post highlights data from Webb science in progress, which has not yet been through the peer-review process.
On the morning of Saturday, Nov. 5, an international team of planetary scientists woke up with great delight to the first Webb images of Saturn’s largest moon, Titan. Here, Principal Investigator Conor Nixon and others on the Guaranteed Time Observation (GTO) program 1251 team using Webb to investigate Titan’s atmosphere and climate describe their initial reactions to seeing the data.
Titan is the only moon in the solar system with a dense atmosphere, and it is also the only planetary body other than Earth that currently has rivers, lakes, and seas. Unlike Earth, however, the liquid on Titan’s surface is composed of hydrocarbons including methane and ethane, not water. Its atmosphere is filled with thick haze that obscures visible light reflecting off the surface.
We had waited for years to use Webb’s infrared vision to study Titan’s atmosphere, including its fascinating weather patterns and gaseous composition, and also see through the haze to study albedo features (bright and dark patches) on the surface. Titan’s atmosphere is incredibly interesting, not only due to its methane clouds and storms, but also because of what it can tell us about Titan’s past and future – including whether it always had an atmosphere. We were absolutely delighted with the initial results.
Team member Sebastien Rodriguez from the Universite Paris Cité was the first to see the new images, and alerted the rest of us via email: “What a wake-up this morning (Paris time)! Lots of alerts in my mailbox! I went directly to my computer and started at once to download the data. At first glance, it is simply extraordinary! I think we’re seeing a cloud!” Webb Solar System GTO Project Lead Heidi Hammel, from the Association of Universities for Research in Astronomy (AURA), had a similar reaction: “Fantastic! Love seeing the cloud and the obvious albedo markings. So looking forward to the spectra! Congrats, all!!! Thank you!”
Thus began a day of frantic activity. By comparing different images captured by Webb’s Near-Infrared Camera (NIRCam), we soon confirmed that a bright spot visible in Titan’s northern hemisphere was in fact a large cloud. Not long after, we noticed a second cloud. Detecting clouds is exciting because it validates long-held predictions from computer models about Titan’s climate, that clouds would form readily in the mid-northern hemisphere during its late summertime when the surface is warmed by the Sun.
We then realized it was important to find out if the clouds were moving or changing shape, which might reveal information about the air flow in Titan’s atmosphere. So we quickly reached out to colleagues to request follow-up observations using the Keck Observatory in Hawai’i that evening. Our Webb Titan team lead Conor Nixon from NASA’s Goddard Space Flight Center wrote to Imke de Pater at University of California, Berkeley, and Katherine de Kleer at Caltech, who have extensive experience using Keck: “We just received our first images of Titan from Webb, taken last night. Very exciting! There appears to be a large cloud, we believe over the northern polar region near Kraken Mare. We were wondering about a quick response follow-up observation on Keck to see any evolution in the cloud?”
After negotiations with the Keck staff and observers who had already been scheduled to use the telescope that evening, Imke and Katherine quickly queued up a set of observations. The goal was to probe Titan from its stratosphere to surface, to try to catch the clouds we saw with Webb. The observations were a success! Imke de Pater commented: “We were concerned that the clouds would be gone when we looked at Titan two days later with Keck, but to our delight there were clouds at the same positions, looking like they had changed in shape.”
After we got the Keck data, we turned to atmospheric modeling experts to help interpret it. One of those experts, Juan Lora at Yale University, remarked: “Exciting indeed! I’m glad we’re seeing this, since we’ve been predicting a good bit of cloud activity for this season! We can’t be sure the clouds on November 4th and 6th are the same clouds, but they are a confirmation of seasonal weather patterns.”
The team also collected spectra with Webb’s Near-Infrared Spectrograph (NIRSpec), which is giving us access to many wavelengths that are blocked to ground-based telescopes like Keck by Earth’s atmosphere. This data, which we are still analyzing, will enable us to really probe the composition of Titan’s lower atmosphere and surface in ways that even the Cassini spacecraft could not, and to learn more about what is causing the bright feature seen over the south pole.
We are expecting further Titan data from NIRCam and NIRSpec as well as our first data from Webb’s Mid-Infrared Instrument (MIRI) in May or June of 2023. The MIRI data will reveal an even greater part of Titan’s spectrum, including some wavelengths we have never seen before. This will give us information about the complex gases in Titan’s atmosphere, as well as crucial clues to deciphering why Titan is the only moon in the Solar System with a dense atmosphere.
Maël Es-Sayeh, a graduate student at the Universite Paris Cité, is particularly looking forward to these observations: “I will be using the data from Webb in my PhD research, so it’s very exciting to finally get the real data after years of simulations. I can’t wait to see what will come in part two next year!”
About the Authors
Conor Nixon, is a planetary scientist at the NASA Goddard Space Flight Center in Greenbelt, Maryland, and serves as Principal Investigator on the Webb Cycle 1 Guaranteed Time Observation program 1251.
Co-Investigator Heidi Hammel is a planetary scientist. She is Vice President for Science at AURA and leads the JWST Solar System Science Group.
Co-Investigator Sébastien Rodriguez is a planetary scientist at the Institut de Physique du Globe de Paris at the Universite Paris Cité, in France.
Imke de Pater is an Emeritus professor of astronomy at the University of California, Berkeley, and is lead of the Keck Titan Observing Team.
Katherine de Kleer is an Assistant Professor of Planetary Science and Astronomy at Caltech in Pasadena, California, and is a member of the Keck Titan Observing Team.
Juan Lora is an Assistant Professor of Earth & Planetary Sciences at Yale University in New Haven, Connecticut.
Maël Es-Sayeh is a graduate student in planetary sciences at Institut de Physique du Globe de Paris of the Universite Paris Cité, in France.
– Margaret W. Carruthers, Office of Public Outreach, Space Telescope Science Institute