- 4084 - JAMES WEBB - 2023 planned explorations . The James Webb Space Telescope (JWST) has accomplished some amazing things during its first year of operations! 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 that existed at Cosmic Dawn.
--------------------- 4084 - JAMES WEBB - 2023 planned explorations
- What Webb will be
studying during its second year of operations?
Approximately 5,000 hours of prime time and 1,215 hours of parallel time
were awarded to programs 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.
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- 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.
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- With Webb’s
superior infrared optics and sensitivity, astronomers look forward to being
able to directly image exoplanets and obtain spectra from their
atmospheres. 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.
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- 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. 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.
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- Using Webb’s
Near-Infrared Spectrometer (NIRSpec) to observe short-period Jupiter-sized
planets around red dwarfs, 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.
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- Another proposal,
“The Hot Rocks Survey,” will examine nine irradiated terrestrial (rocky)
exoplanets that orbit close to their M-type stars. This program will spend
115.2 allotted hours examining rocky planets with MIRI to determine if they
have atmospheres or are barren rocks.
-
- Infrared
photometric capability of JWST/MIRI in imaging mode to observe 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.
-
- Observation time
(82 hours) wil search for the long-theorized class of planets known as “water
worlds.” This 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.
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- They will 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, they will provide vital constraints on the
existence of water worlds and will allow us to start characterizing the
chemical diversity of their atmospheres.
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- 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.
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- 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.
-
- A “JWST Wide Area
3D Parallel Survey.” 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 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):
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- Such a large area
redshift survey will allow astronomers 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.
-
- By taking
ultra-deep images with Webb‘s Near-Infrared Camera (NIRCam), astronomers 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.
-
- Combining the power
of strong gravitational lensing with ultra-deep NIRCam imaging will 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.
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- A deep 6-filter
medium-band imaging survey with the NIRCam will 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 ( the Hubble Tension).
-
- Intergalactic
studies 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?” .
-
- Multiple observations
now indicate that reionization ended well below z = 6, opening the door to new
and more detailed tests of reionization models.
One test concerns the relationship between IGM opacity and density near
the end of reionization.
-
- Mapping the Most
Extreme Protoclusters in the Epoch of Reionization will 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.
-
- General
Observation time will also be dedicated to studying planets, satellites, and
objects in our backyard. 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 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. They will 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.
-
- 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 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.
-
- Webb will conduct
multiple observation campaigns that address questions surrounding stellar
physics, stellar types, and the interstellar medium (ISM). One in particular
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.
-
- They will conduct
detailed studies of massive stars in the Small Magellanic Cloud (SMC), which
would be impossible using any other facility.
Exploiting 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. 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.
-
- NIRSpec will 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.
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- The primary
galaxies have imaging from JWST and HST, and their integrated spectra have been
taken with NIRSpec-MSA. They 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.
-
- 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. Astronomers
will vbe using MIRI data to study the “extreme feedback” caused by outflows on galaxies.
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- The energies 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. 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.
-
- They will be
observing 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.
-
- The full list of
General Observation programs can be found on the STScI website or in the Cycle
2 GO Abstract Catalog.
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-
July 10, 2023 JAMES WEBB
- 2023 planned explorstions 4084
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