Data from the James Webb Space Telescope (JWST) has shown that an exoplanet orbiting a star in the constellation Leo has some of the chemical markers associated with living organisms on Earth. But these are vague clues. So how likely is it that this exoplanet harbors alien life?
Exoplanets are worlds that orbit other stars the sun. The planet in question has a name K2-18b. It is so called because it was the first planet to orbit Earth red dwarf star K2-18. There is also a K2-18c – the second planet to be discovered. The star itself is dimmer and cooler than the sun, meaning we get the same level of light as we do Soilthe planet would have to be much closer to its star than we are.
The system is roughly 124 light-years away, which is astronomically close. So what are the circumstances like on this? exoplanet? This is a difficult question to answer. We have telescopes and techniques powerful enough to tell us what the star looks like and how far away the exoplanet is, but we can’t take direct images of the planet. However, we can work out a few basic principles.
Figuring out how much light hits K2-18b is important for assessing the planet’s life potential. K2-18b orbits closer to its star than Earth: it is about 16% of the distance from Earth to the Sun. Another measurement we need is the star’s power: the total amount of energy it emits per second. The power of K2-18 is 2.3% of that of the sun.
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Using geometry, we can calculate that K2-18b receives approximately 1.22 kilowatts (kW) of solar energy per square meter. This is similar to the 1.36 kW of incoming light we receive on Earth. Although less energy comes from K2-18, it becomes more even because the planet is closer. So far, so good. However, the calculation of incoming light does not take into account clouds or how reflective the planet’s surface is.
When looking at life on other planets, a popular term to use is: habitable zone, which means that water is in a liquid state at an average surface temperature – as this state is considered essential for life. In 2019, the Hubble Space Telescope determined that K2-18b showed signs of water vapor, indicating that liquid water would be present on the surface. It is currently thought that there are large oceans on the planet.
This caused a wave of excitement at the time, but without further evidence it was just an interesting result. Now we have reports on that JWST has identified carbon dioxide, methane and – possibly – the compound dimethyl sulfide (DMS). in the atmosphere. The preliminary detection of DMS is important because it is only produced on Earth by algae. We currently do not know that it can be produced naturally without a life form.
Is there life on K2-18b?
All these clues seem to indicate that K2-18b could be the place to find extraterrestrial life. However, it’s not that simple, because we have no idea how accurate the results are. The method used to determine what is in an exoplanet’s atmosphere involves light from another source (usually a star or galaxy) passing through the edge of the atmosphere and then being observed by us. Any chemical compound will do that absorb light in specific wavelengths which can then be identified.
Imagine it as if you were looking at a light bulb through a glass beaker. When it is empty, you can see through it perfectly. If you fill it with water you can still see through it quite well, but there are some optical effects and colorations, which are the equivalent of hydrogen and dust clouds in room. Now imagine you’ve poured red food coloring – this could be the equivalent of the main chemical compound in a planet’s atmosphere.
But most atmospheres are made up of many chemicals. The equivalent of looking for one of these would be like pouring 50 – probably many more – colored food dyes, in varying amounts, into your glass and trying to identify how much of a particular color is present. It’s an incredibly difficult task with a lot of room for subjective judgments and errors. In addition, the light passing through the atmosphere contains a signal from the star’s chemical components, further complicating the analysis.
Just a few years ago there was a huge interest in it whether life existed on Venusas observations had indicated the presence of phosphine gas, which can be produced by microbes.
However, this finding was later successfully refuted by various studies. If there can be confusion about what is in the atmosphere of a planet right next door, in astronomical terms it is easy to see why analyzing a planet many times further away is a difficult task .
What can we learn from this?
The chances of life on exoplanet K2-18b are low, but not impossible. These results are unlikely to change anyone’s opinion or belief about extraterrestrial life. Instead, they demonstrate the evolving ability to peer into worlds not our own and find more information.
JWST’s strength lies not only in producing incredible photos, but also in delivering them more detailed and precise data about celestial bodies themselves. Knowing which exoplanets harbor water and which do not could provide information about how Earth formed.
Studying the spheres of gas giant exoplanets can contribute to the study of similar worlds in the world Solar systemas Jupiter And Saturn. And identifying CO2 levels indicates how extreme it is greenhouse effect can influence a planet. This is the real power of studying the composition of planetary atmospheres.
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