The James Webb Space Telescope (JWST) has accomplished some amazing things during its first year of operations! In addition to taking the most detailed and breathtaking images ever of iconic celestial objects, Webb completed its first deep field campaign, turned its infrared optics on Mars and Jupiter, obtained spectra directly from an exoplanet’s atmosphere, blocked out the light of a star to reveal the debris disk orbiting it, detected its first exoplanet, and spotted some of the earliest galaxies in the Universe – those that existed at Cosmic Dawn.
Well, buckle up! The Space Telescope Science Institute (STScI) has just announced what Webb will be studying during its second year of operations – aka. Cycle 2! According to a recent STScI statement, approximately 5,000 hours of prime time and 1,215 hours of parallel time were awarded to General Observer (GO) programs. The programs allotted observation time range from studies of the Solar System and exoplanets to the interstellar and intergalactic medium, from supermassive black holes and quasars to the large-scale structure of the Universe.
The proposals granted observation time were selected Cycle 2 Telescope Allocation Committee (TAC), which met in April 2023. The largest proposals (Treasure and Legacy) were reviewed by the Executive Committee (which met virtually from April 17th to 20th) and were awarded more than 75 hours of observation. The smallest proposals were assessed by external reviewers and awarded 15 hours each, while small to medium proposals were reviewed by topical panels and were awarded 35 to 75 hours. The selected programs are an accurate reflection of Webb’s objectives and capabilities.
Here are some examples to give you an idea of what’s in store!
Exoplanets!
One of the most anticipated aspects of the Webb mission is how it will assist with the transition currently taking place in exoplanet science. Whereas astronomers were largely focused on the discovery process in the past, improved instruments, methods, and analytics are shifting the focus toward characterization. To date, the vast majority of exoplanets have been detected by indirect means, which meant that constraints on their habitability had to be inferred based on their parent star, the distance at which they orbited, and their respective masses.
Thanks to Webb’s superior infrared optics and sensitivity, astronomers look forward to being able to directly image exoplanets and obtain spectra from their atmospheres. In particular, they hope to direct Webb’s mirrors toward nearby M-type (red dwarf) stars and their rocky planets, many of which have been confirmed in recent years. In addition to being the most common stars in the Universe (accounting for 75% to 80%), red dwarfs are also likely to support rocky planets within their habitable zones (HZs).
However, these planets are likely to be tidally locked with their suns, and red dwarfs are prone to flare activity, which raises questions about their long-term ability to retain atmospheres. To address this mystery, Dr. Shubham Kanodia of the Carnegie Institution of Washington and his team were awarded 132.39 hours for their program titled “Red Dwarfs and the Seven Giants.” This study will characterize the atmospheres of giant rocky planets around M-type stars to address one of the JWST’s primary science goals: how atmospheric composition can affect a planet’s formation and evolutionary history.
This will consist of Kanodia and his team using Webb’s Near-Infrared Spectrometer (NIRSpec) to observe short-period Jupiter-sized planets around red dwarfs, which pose challenges to current theories about planet formation and represent an extreme regime that is poorly understood. By comparing the atmospheres of seven M-dwarf short-period Jupiters to the gas giants that orbit our Sun, they hope to characterize their atmospheric composition and metallicity and compare them to gas giants that orbit more-massive yellow-white (F-type), Sun-like (G-type), and orange dwarf (K-type) stars.
Another proposal, “The Hot Rocks Survey,” will examine nine irradiated terrestrial (rocky) exoplanets that orbit close to their M-type stars. Led by PI Hannah Diamond-Lowe and her colleagues from the Technical University of Denmark (DTU Space), this program will spend 115.2 allotted hours examining rocky planets with MIRI to determine if they have atmospheres or are barren rocks. As they wrote in their proposal:
“We will use the unique infrared photometric capability of JWST/MIRI in imaging mode to observe our targets as they pass behind their host stars in a secondary eclipse. This method will allow us to efficiently determine which, if any, of the worlds in our sample hint at the presence of atmospheres. Conducting this survey early in the lifetime of JWST will enable us to chart a course to the most promising of our rocky world neighbors to investigate further, or else send us back to the drawing board to invest our time in harder-to-reach cooler targets that are more likely to retain atmospheres.”
Professor Bjorn Benneke of the Universite de Montreal’s Trottier Institute for Research on Exoplanets (iREx) and his colleagues – many of whom are members of the Canadian Space Agency (CSA) – were also awarded observation time (82 hours) to search for the long-theorized class of planets known as “water worlds.” Their proposal, “Exploring the existence and diversity of volatile-rich water worlds,” will rely on JWST’s large aperture, broad infrared wavelength coverage, and ultra-stable platform to unambiguously identify water worlds and characterize their atmospheric compositions. They wrote:
“We will use NIRISS SOSS and NIRSpec G395H to measure atmospheric transmission spectra for a sample of the five most promising water-world candidates identified by their bulk densities, transmission spectroscopy metrics, and the expected depths of molecular spectral features. By surveying multiple targets, our program will provide vital constraints on the existence of water worlds and will allow us to start characterizing the chemical diversity of their atmospheres. The existence of water worlds has important implications for theories of planet formation, and with compositions dominated by volatiles other than H/He, they represent a new regime of atmospheric chemistry that has until now remained uncharted by observations.”
Galaxies
A major focus of the Webb mission is the investigation of Cosmic Dawn, which began roughly one billion years after the Big Bang. Also known as the Epoch of Reionization, this period is so-named because the first galaxies emerged during this time. This led to the reionization of the neutral hydrogen that permeated the intergalactic medium (IGM), causing the Universe to be transparent. This era is considered the “final frontier” of cosmological surveys because the extreme redshift and presence of neutral hydrogen make it impossible to study this period in visible light.
The lack of transparency during this period led to it being nicknamed the “Cosmic Dark Ages.” The only way to detect light from this period is by observing the 21-cm transition line, a part of the radio spectrum inaccessible to modern-day instruments, or the H-alpha emission line, which is visible in the mid-infrared spectrum. According to a recent study, an international team led by the Kapetyn Astronomical Institute (KAI) resolved the H-alpha emission line using data from Webb’s MIRI instrument, thus providing the first confirmed detection of galaxies at Cosmic Dawn.
During Cycle 2, astronomers intend to push the boundaries even farther. For starters, PI Karl Glazebrook of the Swinburne University of Technology and an international team were allotted 615 hours to conduct a “JWST Wide Area 3D Parallel Survey.” This will consist of pure parallel observations using JWST’s Near Infrared Imager and Slitless Spectrograph (NIRISS) of an area covering 1000 square arc-minutes. The resulting survey, they claim, will provide spectra and redshift measurements for 60,000 galaxies from “Cosmic Noon” to Cosmic Dawn (ca. 10-11 billion to 13 billion years ago), from the first stars and galaxies to the birth of the second generation of stars (Population II):
“Such a large area redshift survey will allow us to measure 3D clustering in the cosmic growth era revealing the detailed connection between dark matter halos and assembling baryons. It will also provide a benchmark set of stellar mass functions for complete spectroscopic type defined samples, address the origin of galactic quenching, provide 2D abundance and age measurements of galaxies measuring galactic buildup and provide a census of rare z>11 bright galaxies and other rare objects at all redshifts. The size of the survey will also enable data-driven discovery with advanced machine learning approaches revealing novelties and surprises in the early Universe.”
In addition, PI Hakim Atek of the Institut d’Astrophysique de Paris and colleagues proposed the Gravitational Lensing and NIRCam IMaging to Probe early galaxy formation and Sources of reionization (GLIMPSE) observation campaign. By taking ultra-deep images with Webb‘s Near-Infrared Camera (NIRCam), Atek and his team will observe low-mass galaxies a few hundred million years after the Big Bang. During their 148 hours of observation, they hope to investigate the mechanisms governing galaxy formation, such as gas accretion, star formation, and the subsequent feedback inhibiting further star formation. This, they claim, will achieve three main goals:
“We propose to combine the power of strong gravitational lensing with ultra-deep NIRCam imaging to achieve three main goals, (1) to measure the prevalence of faint galaxies at z>6 to establish, for the first time, key observational benchmarks for galaxy formation models, which have never been confronted to this uncharted territory; (2) strongly constrain the contribution of the faintest galaxies towards cosmic reionization; (3) probe the typical galaxy population during the Dark Ages, that remains out of reach of current programs.”
Professor Daniel Eisenstein of Harvard University and an international team were awarded 137.1 hours for their proposal, “Unveiling the Redshift Frontier with JWST.” This will consist of a deep 6-filter medium-band imaging survey with the NIRCam to identify galaxies at the redshift frontier (z>15). The properties of these very early galaxies will test and inform theories of galaxy formation and allow astronomers to make discoveries about the physics of the early Universe. This includes theories about the possible presence of “Early Dark Energy” to explain the discrepancy between measurements of cosmic expansion (aka. the Hubble Tension).
They also plan to conduct this survey parallel to a deep multi-object spectroscopy campaign conducted with NIRSpec of galaxy candidates in and around the Hubble Ultra Deep Field (HUDF). “These spectra will provide detailed information about individual high-redshift galaxies, not just stacks or averages, allowing us to study the chemical enrichment, stellar populations, star-formation histories, and nuclear black holes in the first billion years of the Universe,” they state.
Intergalactic & At Large
Cycle 2 will also focus on characterizing the space between galaxies and the large-scale structure of the Universe. Similar to the study of the earliest galaxies, these studies will also pay special attention to the Epoch of Reionization. This will include a program titled “How Does Reionization End?” led by PI George Becker of the University of California Riverside. Using data from the NIRCam Wide Field Slitless Spectroscopy observing mode, Becker and his team will address the debate between early- and late-reionization models and determine when precisely the “Cosmic Dark Ages” ended.
“Multiple observations now indicate that reionization ended well below z=6, opening the door to new and more detailed tests of reionization models,” they write. “One such test concerns the relationship between IGM opacity and density near the end of reionization.” Using their 24.7 hours of observation time, Becker and his colleagues will search for particularly bright Lyman-alpha emitters (LAE) – [O III] emitters – along two quasar lines of light to trace the large-scale densities of the IGM around 12.7 billion years ago.
Another proposal by Dr. Feige Wang of the University of Arizona, titled “Mapping the Most Extreme Protoclusters in the Epoch of Reionization,” is to study the clustering of galaxies in the early Universe. This study will test theoretical models that predict the earliest billion Solar-mass SMBHs form from massive dark matter halos and trace the formation of protoclusters in the early Universe. Using the Near Infrared Imager and Slitless Spectrograph (NIRISS) for their allotted 44.7 hours, the team will make wide-field observations of two extreme galaxy overdensities at z~6.6 (<1 billion years after the Big Bang) anchored by luminous quasars identified by Cycle 1 observations.
“The proposed observations will provide the first comprehensive study of the connection between the growth of the first-generation SMBHs, massive dark matter halos, and large-scale structures traced by galaxy overdensities,” they wrote.
Solar System
General Observation time will also be dedicated to studying planets, satellites, and objects in our backyard. For example, Northumbria University Professor Tom Stallard and an international team were awarded 22.2 hours to study Jupiter’s upper atmosphere to learn more about atmospheric loss from gas giants. Understanding how planets lose their atmospheres to space over time due to stellar winds (and other factors) is essential to characterizing exoplanets and understanding the scope of habitability in the Universe.
While this process is relatively well-understood for Earth, there are discrepancies regarding other planets in the Solar System, demonstrating that several characteristics are poorly understood. For this reason, Stallard and his team proposed using the Near-Infrared Spectrometer Integral Field Unit (NIRSpec-IFU) to scan the limp of Jupiter to reveal the energy distribution throughout the atmosphere (based on altitude and latitude). The JWST data will be compared with radio occultation measurements taken by the Juno probe, which continues to study Jupiter’s atmosphere.
Another ambitious program, inspired by the detection of 1I/’Oumuamua and 2I/Borisov, calls for a detailed study and characterization of interstellar objects (ISOs) that will pass through our Solar System in the near future. This program, led by PI Karen Meech of the University of Hawaii, will spend 17.4 hours using the NIRSpec instrument to obtain spectra from an ISO. As Meech and her colleagues state in their proposal, the implications of these observations will be groundbreaking:
“A detailed look at ISOs will provide unparalleled nearby access to the chemical and physical conditions of exoplanet formation. Comets and some asteroids are the largely unaltered remnants of the planetary accretion process, tracing both dust and volatiles – H20, CO, CO2 – in the disk. JWST will reveal detailed information about ISOs that we cannot obtain from the ground, such as size and albedo, properties of solid ices and surface materials, and simultaneous measurements of water, CO and CO2.”
Stars & the ISM
Webb will also conduct multiple observation campaigns that address questions surrounding stellar physics, stellar types, and the interstellar medium (ISM). One in particular, led by Dr. Miriam Garcia from the Centro de Astrobiologia – Instituto Tecnológico de Aeronáutica (CAB-INTA) and multiple ESA members will use Webb to measure the mass loss rates of massive stars. As they indicate, mass loss “is a key physical process ruling the evolution of massive stars” that also plays a role in galactic evolution – especially where the first galaxies in the Universe are concerned.
Using data obtained by Webb’s NIRSpec instrument for just under 67 hours, Dr. Garcia and her colleagues will conduct detailed studies of massive stars in the Small Magellanic Cloud (SMC), which would be impossible using any other facility. “We propose to exploit JWST’s superb sensitivity in the thermal IR to determine the mass-loss rates of SMC O-stars with thin winds for the first time,” they write. “Our results will serve to anchor the physics of radiation-driven wind theory that is so crucial for our understanding of massive star evolution and their impact on the Universe.”
Dr. Hannah Uebler of the University of Cambridge and an international team will also spend 46.28 hours using NIRSpec to search for Population III stars in low-metallicity galaxies that existed 12.888 to 13.15 billion years ago. This hypothesized population of stars was the first in our Universe, believed to have been extremely massive, bright, hot, and with extremely low metallicities. This work will expand on observations by the JWST and Hubble Space Telescope, using their integrated spectra to discern PopIII stars within early galaxies already spotted with the NIRSpec instrument.
“The primary galaxies have imaging from JWST and/or HST, and their integrated spectra have been taken with NIRSpec-MSA,” stated Dr. Uebler and colleagues in their proposal. “Here we propose to map the surroundings of these galaxies with NIRSpec IFS. NIRSpec-IFS has the distinctive imaging-spectroscopic capabilities to disentangle the characteristic spectral features of PopIII stars close to the primary galaxies, in the wavelength range where PopIII features are predicted to be strongest.”
SMBHs & AGNs
Last, but just as significantly, Webb’s observation time will also be dedicated to studying supermassive black holes (SMBHs) and the resulting Active Galactic Nuclei (AGNs), or quasars. These studies will determine the role SMBHs and AGNs play in galactic evolution, where feedback from a galaxy’s center can arrest star formation in the disk, shape the galaxy, and regulate SMBH accretion. Prof. Sylvain Veilleux (University of Maryland) and an international team were awarded 39.23 hours using MIRI data to study the “extreme feedback” caused by outflows on galaxies.
“The energetics of these outflows scale with quasar power, but current data are still missing the critically important coronal-ionized and warm-molecular gas phases to determine if the quasars in these systems actually affect the host evolution,” they write. To resolve this, they will observe a representative set of 13 local Ultraluminous Infrared Galaxies (ULIRGs) with the most powerful outflows observed to date. These will be analyzed using q3dfit software to get a complete census of outflow energetics, constrain the dominant mechanisms behind feedback, and characterize the impact on galactic evolution.
Meanwhile, Dr. Joseph Hora of the Smithsonian Astrophysical Observatory (SAO) and his team were allotted 29.88 hours to observe the region centered on Sagittarius A* (Sgr A*) – the SMBH at the center of the Milky Way. Using MIRI and simultaneous Chandra observations, they plan to take advantage of JWST’s high angular resolution to characterize Sgr A* emissions, constrain models of the accretion, and determine if particle acceleration is what drives observed variations in mid-infrared and X-ray emissions.
Dr. Yoshiki Matsuoka (Ehime University) and his international team were allotted 23 hours with NIRSpec to observe SMBH growth during the Era of Reionization. These observations will address many burning questions about SMBHs, such as when their progenitors first appeared, how long it took for them to grow to millions of solar masses, and how they affected the evolution of their host galaxies over time. For this campaign, Matsuoka and his team will use Webb’s NIRSpec instrument to examine ten candidate galaxies obscured quasars that existed roughly 12.7 billion years ago.
You could say there’s something for everybody in Cycle 2, from characterizing objects in the Solar System to characterizing exoplanets, galaxies, and the large-scale structure of the Universe. Then again, if any proposals or possibilities have been overlooked, I’m sure they can look forward to getting time during Cycle 3 or the many more observation campaigns that will happen between now and the end of Webb’s expected 20-year run! The full list of General Observation programs can be found on the STScI website or in the Cycle 2 GO Abstract Catalog.
Further Reading: STScI
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