XPost: alt.astronomy, alt.fan.heinlein
from
https://www.space.com/james-webb-space-telescope-revolutionizing-astronomy
8 ways the James Webb Space Telescope is already revolutionizing astronomy
By Keith Cooper published 3 days ago
(opens in new tab)
(opens in new tab)
(opens in new tab)
(opens in new tab)
(opens in new tab)
Comments (0)
An artist's depiction of the James Webb Space Telescope at work.
Jump to:
1. Seeing farther into the past
2. What lit up the universe
3. Measuring exoplanet atmospheres
4. Searching for hints of life
5. Cosmic chemistry and galaxy evolution
6. JWST studies the solar system
7. How stars form
8. How space telescopes are built
It's been almost a year since the most ambitious — and costly — space telescope ever built was launched toward the L2 Lagrange point on the
far side of the Earth from the sun.
Following a nerve-shredding deployment that saw its mirrors and
sunshield successfully unfold while navigating 344 potential points of
failure, the $10 billion James Webb Space Telescope (Webb or JWST) has
been churning out fantastic astronomical data since the summer.
Even less than six months into observations, this data is
transformative, and scientists have already used it to make several
important and record-breaking discoveries. JWST was heralded as a
revolutionary telescope before it launched; now that it is in business,
we look at some of the many ways that it is already succeeding in
transforming astronomy.
1. SEEING FARTHER INTO THE PAST THAN EVER BEFORE
Inset are close-ups of two high redshift galaxies seen by JWST. One is
at a redshift of 10.5, the other at 12.5. Most of the foreground
galaxies are part of the Abell 2744 cluster.
Inset are close-ups of two high redshift galaxies seen by JWST. One is
at a redshift of 10.5, the other at 12.5. Most of the foreground
galaxies are part of the Abell 2744 cluster. (Image credit:
NASA/ESA/CSA/T. Treu (UCLA))
To see the precious rare photons from the most distant galaxies in the universe, the bigger the telescope, the better — and space telescopes
don't come bigger than JWST, with its 21-foot (6.5 meters) primary mirror.
But that's only half the job done, because the more distant an object
is, the more its light is redshifted. The farther a galaxy is from us,
the faster it is receding from us because of the expansion of the
universe, so the more its light becomes stretched, shifting the light
toward redder wavelengths.
The most distant galaxies, which are also the earliest galaxies we can
see, emit light that is shifted all the way into near-infrared
wavelengths by the time it reaches Earth. It's this redshift that
prompted scientists to design JWST to specialize in near- and
mid-infrared light.
The combination of the large mirror and infrared vision has enabled JWST
to see more distant, earlier galaxies than astronomers ever have before, promising to transform our understanding how these galaxies form.
Prior to JWST's launch, the most distant known galaxy was one called
GN-z11. It has a redshift of 11.1, which corresponds to seeing the
galaxy as it was 13.4 billion years ago, just 400 million years after
the Big Bang. That was the absolute limit of what telescopes before JWST
could detect.
Click here for more Space.com videos...
CLOSE
But very soon after the first data from JWST was released, that record
was smashed. Astronomers took advantage of foreground galaxy clusters
like Abell 2744 that act as gravitational lenses: Objects of great mass,
such as galaxy clusters, warp space with their gravity, creating a
magnifying lens-like effect that amplifies light from more distant
objects. Astronomers began finding faint, red smudges in the background
of these lenses — and these smudges have turned out to be the most
distant galaxies ever seen.
First was a galaxy at a redshift of 12.5, called GLASS-z12 (GLASS is the
name of a specific survey program, the "Grism Lens-Amplified Survey from Space"). We see this galaxy as it existed 13.45 billion years ago, or
350 million years after the Big Bang, astronomers calculated.
Galaxies with even greater redshifts soon followed. One, nicknamed
Maisie's Galaxy, is seen as it existed just 280 million years after the
Big Bang, at a redshift of 14.3, while another, at redshift 16.7, is
seen just 250 million years after the Big Bang. There have even been
claims for a galaxy at an astounding redshift of 20, which if confirmed
would have existed just 200 million years after the Big Bang.
JWST is also working to confirm these finds as well, using a second
instrument to split light by wavelength. Astronomers have already
confirmed a galaxy with a redshift of 13.2, which we see as it was when
the universe was just 325 million years old.
2. DISCOVERING WHAT LIT UP THE UNIVERSE
An artist's depiction of the universe's path from the Big Bang, at the
right, to the present, at the left; in between, the very first stars and
black holes created enough light to end the cosmic dark ages.
An artist's depiction of the universe's path from the Big Bang, at the
right, to the present, at the left; in between, the very first stars and
black holes created enough light to end the cosmic dark ages. (Image
credit: NASA/STScI)
Following the Big Bang, but before stars and galaxies had formed, the
universe was dark and shrouded in a fog of neutral hydrogen gas.
Ultimately light, particularly ultraviolet radiation, ionized that fog.
But where did that light initially come from to end the cosmic dark ages?
Astronomers believe that light came either from young galaxies filled
with stars, or from active supermassive black holes, which are
surrounded by accretion disks of brilliantly hot gas and shoot powerful
jets into space. The question of which came first — galaxies or their
black holes — is one of the biggest conundrums in cosmology, a kind of chicken or egg question.
Already, JWST has found that the early galaxies it is detecting are
brighter and more structured than expected, with distinct disks around
bulbous cores already filled with stars. This characteristic suggests
that fully-formed galaxies were on the scene quickly — but whether they already contained supermassive black holes remains to be seen.
Fortunately, JWST is designed to answer this question, and when it does
it will provide a huge piece of the jigsaw that is the puzzle of the
early universe.
3. JWST MEASURES EXOPLANET ATMOSPHERE
An artist's impression of the gas giant exoplanet WASP-39b; JWST has characterized its atmosphere.
An artist's impression of the gas giant exoplanet WASP-39b; JWST has characterized its atmosphere. (Image credit: NASA/ESA/CSA/J. Olmsted
(STScI))
Astronomers have now found more than 5,000 exoplanets and counting, but
despite this remarkable haul, we still know next to nothing about many
of them. JWST isn't designed to discover new exoplanets, but it does aim
to paint much more detailed pictures of known worlds by conducting
something called transit spectroscopy.
When a planet passes in front of its star, some of the star's light
filters through the planet's atmosphere, and molecules in the atmosphere
can absorb some of that starlight, creating dark lines in the star's
spectrum, a barcode-like breakdown of light by wavelength. Knowing
what's in a planet's atmosphere, or even whether it has an atmosphere at
all, can teach astronomers about how a planet might have formed and
evolved, what its conditions are like and what chemical processes are
taking place in that atmosphere.
The atmospheric composition of exoplanet WASP-39b.
The atmospheric composition of exoplanet WASP-39b. (Image credit: NASA/ESA/CSA/J. Olmsted (STScI))
Early results have been hugely encouraging. In August, astronomers
announced that JWST had made the first confirmed detection of carbon
dioxide gas in the atmosphere of an exoplanet, in this case WASP-39b,
which is 700 light years-away. Later, in November, astronomers released
a more complete spectrum showing the absorption lines of elements and
molecules in WASP-39b's atmosphere, including not only carbon dioxide
but also carbon monoxide, potassium, sodium, sulfur dioxide and water
vapor.
The findings were described as the most detailed analysis of an
exoplanet's atmosphere yet.
The spectrum showed that there was a lot more oxygen in the planet's
atmosphere than carbon, as well as an abundance of sulfur. Scientists
think that sulfur must have come from numerous collisions that WASP-39b experienced with smaller planetesimals when it was forming, giving us
clues to the planet's evolution that could also hint at how the gas
giants in our own solar system, Jupiter and Saturn, formed. In addition,
the existence of sulfur dioxide is the first example of a product of photochemistry on a planet beyond the solar system, since the compound
forms when a star's ultraviolet light reacts with molecules in a
planetary atmosphere.
4. WEBB SEARCHES FOR HINTS OF LIFE AND HABITABILITY
An artist's depiction of the seven planets in the TRAPPIST-1 system.
An artist's depiction of the seven planets in the TRAPPIST-1 system.
(Image credit: NASA/JPL-Caltech)
Studies of planets such as WASP-39b are one thing, but one of the holy
grails of exoplanet science is to find another planet that is habitable,
like Earth, and JWST is well positioned to characterize alien worlds.
The aforementioned observations of WASP-39b bode well for forthcoming
studies of the planets of the TRAPPIST-1 system of seven rocky planets
orbiting a red dwarf star located 40.7 light-years away from Earth. Four
of these worlds lie in the star's putative habitable zone, where
temperatures would permit liquid water to persist on the surface; given
the right conditions they could potentially be habitable to varying
degrees.
Initial observations with JWST are focusing on TRAPPIST-1c, which is the easiest to observe. Models predict that it will have an atmosphere
similar to Venus, with lots of carbon dioxide. While TRAPPIST-1c is
likely too hot to be habitable, determining whether it has an atmosphere
and, if so, whether that atmosphere possesses carbon dioxide will be a
big step toward characterizing Earth-size worlds. It will also be a big
task, requiring 100 hours of observing time with JWST, which is tackling
about 10,000 hours of observations during its first year of science.
From TRAPPIST-1c, things could become more ambitious, with JWST
targeting the other worlds in the TRAPPIST-1 system that are more likely
to be habitable, as well as similar worlds around other nearby stars. Astronomers will be on the lookout for biosignatures, such as the
presence of both methane and oxygen in an atmosphere. The discovery of photochemical reactions in WASP-39b's atmosphere is also an important
step, since photochemical reactions drive the formation of the
carbon-based molecular building blocks of life.
5. JWST STUDIES COSMIC CHEMISTRY AND GALAXY EVOLUTION
Galaxy mergers, such as that of IC 1623 pictured here, can drive star formation, which in turn increases the chemical abundance of a galaxy.
Galaxy mergers, such as that of IC 1623 pictured here, can drive star formation, which in turn increases the chemical abundance of a galaxy.
(Image credit: ESA–Webb/NASA/CSA/L. Armus & A. Evans)
Some stars live for billions upon billions of years, but others exist
for just a short time before either exploding in a supernova or
expanding to become a red giant that then puffs off its outer layers
into deep space. In both situations, the stars disperse large amounts of
cosmic dust formed from elements heavier than hydrogen and helium across
space.
It turns out that there is a relationship between a galaxy's mass, its star-formation rate and its chemical abundances. Deviations from this relationship at high redshift might indicate that galaxies evolved
differently in the early universe. Prior to JWST, astronomers could only reliably measure the abundances of various elements in galaxies up to a redshift of 3.3; in other words, galaxies that existed about 11.5
billion years ago. But how abundant these heavy elements were in
galaxies earlier than this is a bit of a mystery, and fertile ground for
JWST to really revolutionize our understanding.
Early results from JWST have shown that the relationship between star
formation and mass does hold for galaxies at redshifts as high as 8, but
that their abundance of heavier elements is three times lower than
expected. This discrepancy suggests that stars and galaxies formed more
quickly than we realized, before enough generations of stars had the
chance to die out and disperse their elements into the cosmos.
6. JWST SETS ITS SIGHTS ON THE SOLAR SYSTEM
Brilliant Jupiter, its faint rings and several of its small moons imaged
by JWST.
Brilliant Jupiter, its faint rings and several of its small moons imaged
by JWST. (Image credit: NASA/ESA/Jupiter ERC Team/Ricardo Hueso
(UPV/EHU) and Judy Schmidt)
Although JWST was designed to probe deep space, it can also be used to
observe our nearest neighbors, and the results have been pleasantly
surprising.
Astronomers were not sure what to expect when JWST pointed at Jupiter
because of how fast it moves and how bright the planet is compared to
the faint distant galaxies JWST usually observes. Scientists worried
that Jupiter might overload JWST's sensitive detectors or wipe out
fainter features with its glare, but the results were better than could
be imagined. JWST's images showed Jupiter's faint rings and some of its
small moons, as well as the planet's atmospheric bands and auroras.
By observing in near- and mid-infrared light, with the high resolution
that JWST's giant mirror provides, astronomers are able to peer deeper
into Jupiter's atmosphere to see what's going on beneath the cloud tops
and learn how deeply the clouds extend.
On the left is a simulated map of Mars, and on the right is JWST's image
of thermal emission from the surface of the planet.
On the left is a simulated map of Mars, and on the right is JWST's image
of thermal emission from the surface of the planet. (Image credit: NASA/ESA/CSA/STScI/Mars JWST–GTO team)
JWST has also imaged faraway Neptune, Saturn's moon Titan and Mars.
While JWST's portrait of the Red Planet may not be aesthetically
pleasing, it shows temperature variations on Mars' surface and
absorption by carbon dioxide in its atmosphere. In the future, JWST will observe Mars to track more tenuous gases, such as mysterious seasonal
plumes of methane that could originate in either geological or
biological activity.
7. JWST IS TEACHING US ABOUT STAR FORMATION
JWST's mid-infrared image of the Pillars of Creation.
JWST's mid-infrared image of the Pillars of Creation. (Image credit: NASA/ESA/CSA/STScI/J. DePasquale (STScI)/A. Pagan (STScI))
One of the Hubble Space Telescope's most iconic images was that of the
Pillars of Creation — columns of molecular gas many light-years long
found in the Eagle Nebula. Those columns are cosmic nurseries where
stars are born. JWST has revisited the Pillars of Creation, and the
resulting images in near- and mid-infrared light are just as special as
the original.
But the new views are also more than just pretty pictures. JWST's
infrared vision is able to penetrate through the dust in the Pillars to
gain a better view of the star formation going on inside, showing knots
of molecular gas on the verge of collapsing into nascent stars. When
those stars are just a few hundred thousand years old, they begin to
shoot out jets that erode the edges of the Pillars.
Elsewhere, JWST has provided one of the most detailed looks at such a protostar, known as L1527, and how it is interacting with the molecular
gas that is accreting onto it, prompting outbursts that are clearing out
two cavities in the butterfly-shaped nebula.
Before JWST, optical observations of young stars were limited because
dust blocks their light. Radio and submillimeter observations can detect
some of what is going on, and previous infrared telescopes could see
broad strokes but nothing detailed. JWST now offers the resolution
necessary to reveal the secrets of star formation in far greater detail
than ever before.
8. JWST CHANGED HOW SPACE TELESCOPES ARE BUILT
JWST's 6.5-meter segmented mirror is an innovation that will be used on
many large space telescope in the future.
JWST's 6.5-meter segmented mirror is an innovation that will be used on
many large space telescope in the future. (Image credit: NASA/Chris Gunn)
JWST took a lot of trouble and money to eventually get into orbit. Years overdue and billions of dollars over-budget, its revolutionary design
has nevertheless blazed a new trail for space telescopes. In particular,
its massive, golden primary mirror, formed by unfolding 18 hexagonal
segments, was brand-new engineering to permit a telescope of such great
size to be launched into space.
In the future, the effort of designing and building JWST will pay off
not only in the revolutionary scientific discoveries that it will make,
but also in how it will inspire the design of the next generation of
large space telescopes.
The U.S. National Academies' decadal report on the astrophysics
priorities over the next 10 years recommends as the top-priority project
the development of a large optical and ultraviolet telescope to replace
Hubble sometime in the 2040s. This telescope would have at minimum a
mirror diameter of 26 feet (8 m), a feat that can be achieved only by
the segmented design pioneered by JWST.
The size of a rocket no longer constrains the size of your telescope; if
it doesn't fit inside the rocket faring then the telescope can be folded
up, just like JWST was. Whatever discoveries these future space
telescopes make, we will have JWST to thank.
Follow Keith Cooper on Twitter @21stCenturySETI. Follow us on Twitter @Spacedotcom and on Facebook.
Join our Space Forums to keep talking space on the latest missions,
night sky and more! And if you have a news tip, correction or comment,
let us know at:
community@space.com.
Keith Cooper
Keith Cooper
Contributing writer
Keith Cooper is a freelance science journalist and editor in the United Kingdom, and has a degree in physics and astrophysics from the
University of Manchester. He's the author of "The Contact Paradox:
Challenging Our Assumptions in the Search for Extraterrestrial
Intelligence" (Bloomsbury Sigma, 2020) and has written articles on
astronomy, space, physics and astrobiology for a multitude of magazines
and websites.
--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)