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| The luminous, hot star Wolf-Rayet 124 (WR 124), which lies about 15,000 light-years from Earth, is prominent at the center of this James Webb Space Telescope composite image, which combines near-infrared and mid-infrared wavelengths of light from Webb's Near-Infrared Camera and Mid-Infrared Instrument. NASA released this image on March 14, 2023. (Image credit: NASA, ESA, CSA, STScI, Webb ERO Production Team) |
The James Webb Space Telescope has dazzled us plenty already, but the best is
yet to come from the observatory, mission team members say.
"We have a lot of fantastic work that's coming out from the telescope,"
Stefanie Milam, the James Webb Space Telescope (JWST) deputy project
scientist for planetary science, told the audience Tuesday (March 14) at the
South by Southwest (SXSW) Conference and Festivals in Austin, Texas.
"The science community is really working hard on analyzing their own data
and putting it into scientific peer-reviewed publications, and that is now
finally coming to fruition," added Milam, of the Astrochemistry Lab at
NASA's Goddard Space Flight Center in Greenbelt, Maryland.
A sensational, newly released JWST image of WR 124, a huge, exotic star that
has already shed about 10 times the mass of the sun, is one example. The
splendor of the image — taken last summer, just after JWST began its science
operations — is illustrative of how the telescope's near- and mid-infrared
instruments, in combination with the superior optics of its 21.3-foot-wide
(6.5 meters) mirror, are able to show astronomers details they have never seen
before.
In the case of WR 124, the data from the Near-Infrared Camera (NIRCam) and
the Mid-Infrared Instrument (MIRI) reveal the clumpy structure of the dust
surrounding WR 124, allowing astronomers to better understand how the dust
is produced, the size and quantity of dust particles present, and how dust
from other such "Wolf-Rayet" stars contributes to the Milky Way's overall
dust content, which is then recycled in the next generation of stars and
planets.
"One area where we're really getting a lot of new information is the birth
of stars," Milam said at the SXSW event. "[We're] understanding star
formation in a way that we've never really had access to, with this whole
new sensitivity and detail that we've never had before. Not only are we
seeing star formation in our own galaxy, but even in other galaxies … and
we're getting this detail now that we used to only have for our own galactic
understanding, now expanding into these other galaxies across the universe.
It's just really an exciting time to be part of that field and understand
how our sun was born and how the solar system was formed, and this is giving
us that first real glimpse of it."
By peering through the clouds of dusty gas that envelop star-forming regions
that are opaque at visible wavelengths of light, JWST's infrared vision is
able to tease out these important details. But astronomers don't just want
to learn about how stars and planets form; they also want to learn more
about how they evolve. That's where the WR 124 observations come in — the
central star shedding the nebula from its outer layers has a mass 30 times
that of our sun and will eventually explode as a supernova. JWST is also
promising to do the same for planets.
The planets of our solar system are one starting point. "We will be
observing the solar system with the James Webb Space Telescope, and have
been doing so," said Milam. Superb images of Mars, Jupiter and Neptune have
already been released by the JWST team, as well as observations of the DART
impact on the asteroid Dimorphos in September 2022.
"We're going to be observing everything in our solar system that JWST can
point to, from near-Earth asteroids, comets, interstellar objects, all of
the planets and their satellites to the farthest reaches of our solar
system, including our favorite minor planet, Pluto," said Milam. "So,
there's lots more to come."
Beyond our solar system are more planets orbiting other stars. More than
5,000 exoplanets have been discovered to date, ranging in size from massive
giants larger than Jupiter to small worlds the size of Mars. However, the
easiest exoplanets to study have been the hot Jupiters — gas giants orbiting
very close to their host star, at orbital radii of just a few million miles
— because they produce the strongest signal.
JWST's earliest exoplanet results have also come from hot Jupiters — for
instance WASP-39b, a giant planet 700 light-years away. JWST conducts what
is called transit spectroscopy, in which, as the planet transits (moves
across) the face of its star, some of that starlight passes through the
planet's atmosphere. This light is absorbed by molecules within the planet's
atmosphere, and different molecules absorb light at different wavelengths.
JWST's spectrum of WASP-39b's atmosphere — showing the absorption lines,
which allow astronomers to identify the molecules involved — is the most
detailed look at an exoplanet's atmosphere yet conducted.
"We've already seen that JWST data is is just so good, so precise, that we
are able to detect additional molecules in these distant exoplanet
atmospheres that we've never really expected to see," said NASA Goddard's
Knicole Colon, who also spoke at the SXSW event and who is JWST's deputy
project scientist for exoplanet science.
One of these molecules, sulfur dioxide, was created in WASP-39b's atmosphere
by photochemical reactions. In other words, by the action of sunlight on
atoms and molecules in the atmosphere.
"We literally didn't think we'd be able to see [the results of these
chemical reactions] with JWST," said Colon. "Even though we knew it'd be a
great telescope, [the detection of sulfur dioxide was] still just that much
better than expected."
This means that, as JWST studies and characterizes more and more exoplanets,
new and exciting discoveries will almost certainly be on the menu,
discoveries that will be able to teach astronomers about the formation and
evolution of those planets. The mixture of gases in a planetary atmosphere,
for instance, can give some indication as to how far from its star the
planet formed.
Prior to JWST, studies of exoplanetary atmospheres were limited to hot
Jupiters, but JWST is now beginning to target the atmospheres of smaller,
Earth-sized planets, too. Observations of the rocky worlds of the TRAPPIST-1
system, for example, are ongoing, but because these planets are much smaller
than hot Jupiters and orbit a faint red dwarf star, it will take longer for
JWST to tease out the details from their atmospheres, if they even have
atmospheres. However, in the next few years, some of the results from the
TRAPPIST-1 planets and other similar worlds could transform how we view our
own planet Earth in a cosmic context.
"We're still very much in the early days of deciphering all the exoplanet
data," said Colon. "What we do want to do is compare those systems and say,
'Do they have any similarities to Earth?' I'm excited to see what we learn
about those planets that are around the same size as our own. They might not
always be the same temperature, they might not have surfaces with liquid
oceans and all that, but we expect to still learn about their overall
atmosphere. Is water in the atmosphere? Is there carbon dioxide? Is there
anything familiar to us that we can connect to and relate to help us
understand better [whether] there is other life out there?"
Whatever those answers are, they are coming, and the next few years are
going to be tremendously exciting as JWST makes discoveries that could
ultimately become historic milestones.
"The first couple of years of science with JWST is going to open the door to
huge new questions and challenges that we have ahead of us on whether or not
there could be life on another planet," said Milam.
Another mystery that captures the imagination just as much as the search for
habitable exoplanets is that of the dark universe, specifically dark matter,
which is the mysterious substance held responsible for the extra gravity
observed in galaxies and galaxy clusters, and dark energy, the unknown force
that is driving the acceleration in the expansion of the universe.
"We think that about 75% of the whole energy-matter content of the universe
is this mysterious thing that we call dark energy, and another 20% is this
other mysterious stuff called dark matter," said Milam. "When astronomers
don't know what something is, we label it dark. It's astounding … the
hundreds of billions of galaxies and the trillions of stars and countless
planets, all of that only makes up about 5% of the whole universe. And the
rest, the other 95%, we don't know what it is."
Dark matter is located in invisible haloes that surround galaxies, leading
Milam to describe dark matter as the "scaffolding" in which galaxies sit.
"JWST is going to help us in learning specifically about dark matter," said
Milam. "By studying how galaxies change over time, we're able to learn more
about dark matter."
JWST won't be able to discover what dark matter is; that's up to the
particle physicists. But by watching how dark matter behaves around
galaxies, astronomers will be able to constrain some of its properties,
which could help physicists nail down its nature. Researchers have been
asking this question since Vera Rubin first identified the presence of dark
matter in the 1970s, and JWST could help astronomers take some giant leaps
forward in our understanding.
Meanwhile, the new discoveries from JWST keep on coming.
"I can say we have a lot of fantastic work that's coming out from the
telescope," says Milam. "We have a queue of press releases for future
publication that are coming out, so it is a very exciting time. Every week
we release something, so just stay tuned and I'm sure you'll be astounded."
Source 1: Space.com Source 2: SXSW
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Space & Astrophysics