- The planet, called K2-18 B, is 8.6 times the mass of the earth.
- It is located about 124 light years from the earth.
- Scientists do not announce the discovery of real extraterrestrial life.
In a potential monument discovery, scientists using the James Webb space telescope have obtained what they call the strongest signs of possible life beyond our solar system, detecting in the atmosphere of an extraterrestrial planet, the chemical fingerprints of gases on earth are only produced by biological processes.
The two gases – dimethyl sulfide, or DMS, dimethyl disulfide, or DMDS – involved in webb observations on the planet called K2-18 B are generated on earth by living organisms, mainly the microbial life such as sea phytoplankton – algae.
This suggests that the planet can group microbial life, the researchers said. However, they pointed out that they do not announce the discovery of real living organisms but rather a possible biosignature – an indicator of a biological process – and that the results must be considered with caution, with more necessary observations.
Nevertheless, they expressed the excitement. These are the first clues of an extraterrestrial world that may be inhabited, said astrophysicist Nikku Madhusudhan from the Astronomy Institute of the University of Cambridge, the main author of the study published in the magazine Astrophysique Letters.
“This is a transformational moment in the search for life beyond the solar system, where we have shown that it is possible to detect biosignatures in potentially habitable planets with current installations. We have entered the era of observational astrobiology,” said Madhusudhan.
Madhusudhan noted that there are various efforts in search of signs of life in our solar system, including various affirmations of environments that could be conducive to life in places like Mars, Venus and various iced moons.
K2-18 B is 8.6 times more massive than the earth and has a diameter about 2.6 times larger than our planet.
It orbit in the “living area” – a distance where liquid water, a key to life ingredient, can exist on a planetary surface – around a smaller and less luminous red dwarf star than our sun, located about 124 light years from the earth in the Constellation Leo. A light year is the distance that the light moves in one year, 5.9 miles (9.5 miles of kilometers). Another planet was also identified in orbit around this star.
A “hycean world”
About 5,800 planets beyond our solar system, called exoplanets, have been discovered since the 1990s. Scientists have hypothesized the existence of exoplanets called Hyceans-covered with a liquid ocean habitable by microorganisms and an atmosphere rich in hydrogen.
Previous observations of webb, which were launched in 2021 and became operational in 2022, had identified methane and carbon dioxide in the atmosphere of K2-18 B, the first time that carbon molecules were discovered in the atmosphere of an exoplanet in the habitable area of a star.
“The only scenario that currently explains all the data obtained so far from JWST (James Webb space telescope), including past and present observations, is one that K2-18 B is a world of cycenes teeming with life,” said Madhusudhan. “However, we must be open and continue to explore other scenarios.”
Madhusudhan said that with the Hyceens worlds, if they exist, “we are talking about microbial life, perhaps as what we see in the oceans of the earth.” Their oceans are supposed to be warmer than those of the earth. Asked about any multicellular organizations or even intelligent life, Madhusudhan said: “We will not be able to answer this question at this stage. The basic hypothesis is a simple microbial life.”
The DMS and the DMDs, both of the same family of chemicals, were predicted as important exoplanet biosignatures. Webb noted that one or the other, or perhaps both, was present in the atmosphere of the planet at a confidence level of 99.7%, which means that there is still 0.3% like that observation is a statistical stroke of luck.
The gases were detected at atmospheric concentrations of more than 10 parts per million in volume.
“For reference, this is thousands of times higher than their concentrations in the earth’s atmosphere, and cannot be explained without biological activity based on existing knowledge,” said Madhusudhan.
Scientists not involved in the study advised the circumspection.
“The rich data of K2-18 B makes it an enticing world,” said Christopher Glein, principal scientist of the Southwest Research Institute’s Spatial Sciences Division in Texas. “These latest data is a precious contribution to our understanding. However, we must be very careful to test the data as completely as possible. I can’t wait to see additional independent work on data analysis from next week.”
Transit method
K2-18 B is part of the class of “sub-neptune” planets, with a diameter higher than that of the earth but less than that of Neptune, the smallest gas planet of our solar system.
To verify the chemical composition of the atmosphere of an exoplanet, astronomers analyze the light of its host star when the planet passes before it from the point of view of the earth, called transit method. As the transit planet, webb can detect a decrease in stellar light, and a small fraction of the light of the stars goes through the planetary atmosphere before being detected by the telescope. This allows scientists to determine the constituent gases of the planet’s atmosphere.
The previous webb observations of this planet have provided a provisional touch of DMS. His new observations have used a different instrument and a range of light in different wavelengths.
The “Saint Grail” of the science of exoplanets, said Madhusudhan, is to find proof of life on a planet in the shape of a earth beyond our solar system. Madhusudhan said that our species for thousands of years wondered “are we alone” in the universe, and that we could now be in a few years to detect a possible extraterrestrial life in a Hycean world.
But Madhusudhan has always urged caution.
“We must first repeat the observations two to three times to make sure that the signal we see is robust and to increase the significance of detection” at the level of a statistical stroke of luck are less than about one in one million, said Madhusudhan.
“Second, we need more theoretical and experimental studies to ensure whether or not there is another abiotic mechanism (one not involving biological processes) to make DMS or DMDs in a planetary atmosphere like that of K2-18 B. Even if previous studies have suggested (like) robust biosignatures, even for K2-18 B, we need to stay open and continue to stay open and Possibilities “, even for K2-18 B, we need to stay open and continue other possibilities”, even for K2-18 B.
Thus, the conclusions represent “a great if” on the question of whether the observations are due to life, and he is in “no one pretends prematurely that we have detected life,” said Madhusudhan.
