- 4157 - LIFE ON PLANETS - discoveries in their atmospheres? - Astronomers are excited about CO2 and methane being discovered in the atmosphere of an alien world. Are we alone? This question is nearly as old as humanity itself. Today this question in astronomy focuses on finding life beyond our planet. Is there life somewhere else?
---------- 4157 - LIFE ON PLANETS - discoveries in their atmospheres?
- Usually this question inspires visions of
weird, green versions of humans. However, life is more than just us: animals,
fish, plants and even bacteria are all the kinds of things we seek signs of in
space.
-
- Life on Earth is that it leaves traces in
the chemical makeup of the atmosphere. So traces like that, which are visible
from a long way away, are something we look for when hunting aliens.
-
- Scientists reported some very interesting
chemical traces in the atmosphere of a planet called “K2-18b”, which is about
124 light-years from Earth. They may
have detected a substance which on Earth is only produced by living things.
-
- Discovered in 2015 by the Kepler Space
Telescope's K2 mission, it is a type of planet called a sub-Neptune. These are smaller than Neptune in our own
solar system. The planet is about eight and a half times heavier than Earth,
and orbits a type of star called a red dwarf, which is much cooler than our
sun.
-
- K2-18b orbits much closer to its star than
Neptune does, called the “habitable
zone”. This is the area that is not too hot and not too cold, where liquid
water can exist (instead of freezing to ice or boiling into steam).
-
- Earth is what is called a rocky planet, but
sub-Neptunes are gas planets, with much larger atmospheres containing lots of
hydrogen and helium. Their atmosphere can also contain other elements.
-
- The planet was first discovered by the
Kepler Space Telescope, which was monitoring distant stars and hoping for
planets to pass in front of them. When a planet does pass between us and a
star, the star becomes momentarily dimmer which is what tells us a planet is
there.
-
- By measuring how big the dip in brightness
is, how long it takes for the planet to pass in front of the star, and how
often it happens, we can work out the size and orbit of the planet.
-
- The James Webb Space Telescope, launched at
the end of 2021, has now observed and measured the atmosphere of this
exoplanet. The telescope did this by
measuring the color of light so finely, it can detect traces of specific atoms
and molecules. This process, spectroscopy, is like measuring the fingerprint of
elements.
-
- The atmosphere of the exoplanet K2-18b
showed strong signs of methane and carbon dioxide, as well as a weak indication
of dimethyl sulfide. Each element and
molecule has its own color signature. If you can look at the color signature,
you can work out what elements or compounds are in the planet.
-
- While the planet does not have its own
light, astronomers waited for when K2-18b passed in front of its star, and
measured the starlight as it went through the planet's atmosphere, allowing the
team to detect fingerprints of substances in the atmosphere.
-
- The new study found a lot of carbon dioxide
and methane. This is interesting as this is like what is found on Earth, Mars,
and Venus in our solar system rather than Neptune.
It also
found a small amount of dimethyl sulfide. Dimethyl sulfide is an interesting
molecule, made up of carbon, hydrogen, and sulfur.
-
- On Earth, it's generally a bit smelly. But
it's also closely linked to life. The
only process we know that creates dimethyl sulfide on our planet is life. In
particular, marine life and plankton emit it in the form of flatulence.
-
- While on Earth, dimethyl sulfide is linked
to life, on other planets it may somehow be related to geological or chemical
processes. K2-18b is something like
Neptune. Researchers also discovered
that clouds on Neptune are strongly linked to the sun's 11-year cycle of
activity. We have a lot to learn about planets and their atmospheres.
-
- The meaTsurement of dimethyl sulfide is very
subtle, not nearly as strong as the carbon dioxide and methane. This means more
detailed measurements, to improve the strength of the signal, are required.
-
- New space telescopes, like Europe's PLATO
which is under construction, will also help us get a better look at alien
atmospheres. While the signs of
dimethyl sulfide on K2-18b may not be linked to life, they are still an
exciting prospect. There is plenty more to explore.
-
-
September 17, 2023 LIFE
ON PLANETS -
discoveries? 4157
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