The Webb Space Telescope has detected an exoplanet with water, methane, and traces of a chemical that
only arise from life on earth.
That chemical, dimethyl sulfide (DMS), is produced by phytoplankton, basically
algae, on earth.
Needless to say, this could be yet another false alarm. There may be other
golological or astronomical processes that can produce DMS, but I am a bit
excited about this.
Also, this gives me the opportunity to quote Star Trek ……… Sort of.
It turns out that the line comes from a Star Trek filk, but still, I'm
stoked to say the line:
A new investigation with NASA’s James Webb Space Telescope into K2-18 b, an
exoplanet 8.6 times as massive as Earth, has revealed the presence of
carbon-bearing molecules including methane and carbon dioxide. Webb’s
discovery adds to recent studies suggesting that K2-18 b could be a Hycean
exoplanet, one which has the potential to possess a hydrogen-rich atmosphere
and a water ocean-covered surface.
The first insight into the
atmospheric properties of this habitable-zone exoplanet came from
observations with NASA’s Hubble Space Telescope, which prompted further
studies that have since changed our understanding of the system.
K2-18
b orbits the cool dwarf star K2-18 in the habitable zone and lies 120
light-years from Earth in the constellation Leo. Exoplanets such as K2-18 b,
which have sizes between those of Earth and Neptune, are unlike anything in
our solar system. This lack of equivalent nearby planets means that these
‘sub-Neptunes’ are poorly understood, and the nature of their atmospheres is
a matter of active debate among astronomers.
The suggestion that
the sub-Neptune K2-18 b could be a Hycean exoplanet is intriguing, as some
astronomers believe that these worlds are promising environments to search
for evidence for life on exoplanets.
"Our findings underscore the
importance of considering diverse habitable environments in the search for
life elsewhere," explained Nikku Madhusudhan, an astronomer at the
University of Cambridge and lead author of the paper announcing these
results. "Traditionally, the search for life on exoplanets has focused
primarily on smaller rocky planets, but the larger Hycean worlds are
significantly more conducive to atmospheric observations."
The
abundance of methane and carbon dioxide, and shortage of ammonia, support
the hypothesis that there may be a water ocean underneath a hydrogen-rich
atmosphere in K2-18 b. These initial Webb observations also provided a
possible detection of a molecule called dimethyl sulfide (DMS). On Earth,
this is only produced by life. The bulk of the DMS in Earth’s atmosphere is
emitted from phytoplankton in marine environments.
Spectra of K2-18 b, obtained with Webb’s NIRISS (Near-Infrared Imager and
Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph), display
an abundance of methane and carbon dioxide in the exoplanet’s atmosphere,
as well as a possible detection of a molecule called dimethyl sulfide
(DMS). The detection of methane and carbon dioxide, and shortage of
ammonia, support the hypothesis that there may be a water ocean underneath
a hydrogen-rich atmosphere in K2-18 b. K2-18 b, 8.6 times as massive as
Earth, orbits the cool dwarf star K2-18 in the habitable zone and lies 120
light-years from Earth.
Credits: Illustration: NASA, CSA, ESA, R. Crawford (STScI), J. Olmsted
(STScI), Science: N. Madhusudhan (Cambridge University)
The inference of DMS is less robust and requires further validation.
“Upcoming Webb observations should be able to confirm if DMS is indeed
present in the atmosphere of K2-18 b at significant levels,” explained
Madhusudhan.
While K2-18 b lies in the habitable zone, and is now known to harbor
carbon-bearing molecules, this does not necessarily mean that the planet can
support life. The planet's large size — with a radius 2.6 times the radius of
Earth — means that the planet’s interior likely contains a large mantle of
high-pressure ice, like Neptune, but with a thinner hydrogen-rich atmosphere and
an ocean surface. Hycean worlds are predicted to have oceans of water. However,
it is also possible that the ocean is too hot to be habitable or be liquid.
"Although this kind of planet does not exist in our solar system, sub-Neptunes
are the most common type of planet known so far in the galaxy," explained team
member Subhajit Sarkar of Cardiff University. “We have obtained the most
detailed spectrum of a habitable-zone sub-Neptune to date, and this allowed us
to work out the molecules that exist in its atmosphere.”
Characterizing the atmospheres of exoplanets like K2-18 b — meaning
identifying their gases and physical conditions — is a very active area in
astronomy. However, these planets are outshone — literally — by the glare of
their much larger parent stars, which makes exploring exoplanet atmospheres
particularly challenging.
The team sidestepped this challenge by
analyzing light from K2-18 b's parent star as it passed through the exoplanet's
atmosphere. K2-18 b is a transiting exoplanet, meaning that we can detect a drop
in brightness as it passes across the face of its host star. This is how the
exoplanet was first discovered in 2015 with NASA’s K2 mission. This means that
during transits a tiny fraction of starlight will pass through the exoplanet's
atmosphere before reaching telescopes like Webb. The starlight's passage through
the exoplanet atmosphere leaves traces that astronomers can piece together to
determine the gases of the exoplanet's atmosphere.
"This result was
only possible because of the extended wavelength range and unprecedented
sensitivity of Webb, which enabled robust detection of spectral features with
just two transits," said Madhusudhan. "For comparison, one transit observation
with Webb provided comparable precision to eight observations with Hubble
conducted over a few years and in a relatively narrow wavelength range."
"These results are the product of just two observations of K2-18 b,
with many more on the way,” explained team member Savvas Constantinou of the
University of Cambridge. “This means our work here is but an early demonstration
of what Webb can observe in habitable-zone exoplanets.”
The team’s
results were accepted for publication in
The Astrophysical Journal Letters.
The team now intends to conduct follow-up research with the
telescope's MIRI (Mid-Infrared Instrument) spectrograph that they hope will
further validate their findings and provide new insights into the environmental
conditions on K2-18 b.
"Our ultimate goal is the identification of
life on a habitable exoplanet, which would transform our understanding of our
place in the universe," concluded Madhusudhan. "Our findings are a promising
step towards a deeper understanding of Hycean worlds in this quest."
Yeah, I know, it's not supposed to be about my ability to pseudo-quote Star Trek, but it IS about about my ability to pseudo-quote Star Trek for me.
Don't mock me for this.
OK, you can mock me for this.
*I've been waiting my whole life to say that.
