প্রকাশ: 14/07/2022
The powerful James
Webb Space Telescope's inaugural batch of images has opened a new chapter of
cosmic exploration, but astronomers say the observatory's most consequential
discoveries may well be those they have yet to even imagine.
Distant colliding galaxies, gas-giant exoplanets and dying
star systems were the first celestial subjects captured by the
multibillion-dollar observatory, putting its wide range of infrared-imaging
capabilities on colorful display and proving the telescope works as designed.
Webb's gallery of early photos and spectrographic data,
which astronomers likened to the results of mere "target practice" as
they readied the telescope for operational science, also previewed several
planned areas of inquiry ahead.
The competitively-selected agenda of research includes
exploring the evolution of early galaxies, the life cycle of stars, the search
for habitable planets orbiting distant suns, and the composition of moons in
our own outer solar system.
But the most revolutionary findings by Webb, 100 times more
sensitive than its 30-year-old predecessor, the still-operational Hubble Space
Telescope, may turn out to be accidental discoveries or answers to questions
astronomers have yet to ask.
"Who knows what's coming for JWST. But I'm sure we're
going to have a lot of surprises," René Doyon, principal investigator for
one of Webb's instruments, the Near-Infrared Imager and Slitless Spectrograph,
said Tuesday at NASA's Goddard Space Flight Center in Maryland, where the
agency unveiled the observatory's first full-color images.
With Webb open for business seven months after its launch in
December, astronomers are preparing for "something that's out there that
we never guessed would be there at all," said John Mather, a Nobel
Prize-winning senior astrophysicist at NASA whose work during the 1990s helped
cement cosmology's 'Big Bang' theory.
DARK MATTER, DARK ENERGY
Mather and other scientists pointed to dark matter, an
invisible and little-understood but theoretically influential cosmic
scaffolding, as an enigma that Webb might unlock during its mission.
Hubble, likewise, opened a whole new field of astrophysics
devoted to another mysterious phenomenon, dark energy, as its observations of
supernovas led to the unexpected discovery that the universe's expansion is
accelerating.
Taken together, dark energy and dark matter are now
estimated by scientists to account for 95% of the known universe. All the
galaxies, planets, dust, gases and other visible matter in the cosmos compose
just 5%.
"Those were huge surprises," Mather said of early
dark matter and dark energy discoveries.
Amber Straughn, a deputy project scientist working with
Webb, said: "It's hard to imagine what we might learn with this
hundred-times-more-powerful instrument that we really don't know yet."
Dark matter already has figured prominently in Webb's very
first "deep field" image, a composite photo of a distant galaxy
cluster, SMACS 0723, that offers the most detailed glimpse to date of the early
universe thanks to a magnifying effect called a gravitational lens.
The sheer combined mass of galaxies and other unseen matter
in the foreground of the image warps the surrounding space enough to amplify
light coming from more distant galaxies behind them, bringing into view fainter
objects farther away, and thus further back in time.
At least one of the tiny specks of light
"photo-bombing" the edge of the picture dates back 13.1 billion
years, or nearly 95% of the way to the Big Bang, the theoretical cosmic
flashpoint that put the universe in motion 13.8 billion years ago.
But because the calculated combined mass of all the visible
matter in the foreground is insufficient by itself to produce the faint
circular distortion seen in the image, the lensing effect is firm indirect
evidence of dark matter's presence.
"It's the most powerful tool that we have,
astrophysically, to do this type of lensing experiment," said Jane Rigby,
a Webb operations project scientist. "We can't directly detect dark
matter, but we see its impact... we can see its effects in action."
"The universe has been out there, we just had to build
a telescope to see what was there," she added.
New light was also shed unexpectedly from Webb's first
spectrographic analysis of an exoplanet in a distant solar system, in this case
a gas giant roughly the size of Jupiter dubbed WASP-96 b.
Measuring the wavelengths from light filtered through the
atmosphere of the exoplanet as it orbited its own sun clearly revealed the
molecular signature of water vapor in clouds and haze, features scientists were
surprised to find.
"There are discoveries in these data," Webb
program scientist Eric Smith said. "We're making discoveries and we really
haven't even started trying yet."
- Reuters
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