Discovery of a key planet in the quest for life beyond the solar system

Searching for traces of life on Mars, as NASA is currently doing, is one thing. But scientists see further. Could it be possible to find it outside of our solar system?

A study, published in the prestigious journal Science Thursday, reveals the discovery of a new exoplanet, which seems to be an ideal candidate for looking for an atmosphere, and in fine, traces of life around a star other than our Sun.

“The final goal is to find biological markers, biosignatures, in the atmospheres of exoplanets, that is to say signs of life on habitable planets similar to Earth,” José explained to AFP. A. Caballero, astronomer at the Centro de Astrobiologia in Spain. He is one of the co-authors of the study, to which researchers from five continents contributed.

About 4,000 exoplanets have been discovered over the past 25 years, and a few have already shown to have an atmosphere. But these were “big gaseous or icy planets,” says Caballero. This research “has not yet been carried out on planets the size of Earth.”

With their discovery, the researchers have now opened up the possibility of studying an exoplanet “rocky in nature like the Earth”, which could have an atmosphere “which resembles our own”.

“We think she probably has one,” he said.

– 26 light years –

The name of this exoplanet? Gliese 486 b. It is about 30% larger than the Earth, but is 2.8 times heavier, and is found in what is called the habitable zone around a star.

It is “only” 26 light years away, making it the third closest known exoplanet in transit, that is, on a path where it is seen passing in front of its star.

To identify it, the researchers used two different techniques: observing the change in the light emitted by the star as the planet passes in front of it, and radial speed, which measures the star’s “oscillations” below it. influence of the planet’s gravity.

As Gliese 486 b is very close to its star, it takes just under 1.5 days to orbit around it. In addition, the star (named Gliese 486) is very bright. These two factors made it possible to acquire a lot of data, and therefore to study it with such precision.

“We reviewed 350 red dwarf stars looking for signs of small planets,” said Trifon Trifonov, researcher at the Max Planck Institute for Astronomy, and lead author of the study.

– Lava and volcanoes –

But the proximity of this exoplanet to its star also makes it very hot (at least 430 ° C). It is “dotted with volcanoes and rivers of lava,” Trifonov describes. Thus, “it is not habitable”.

However, if this planet “has an atmosphere, then all planets farther away (from the star) with similar characteristics will have an atmosphere,” and more likely to be habitable, says José A. Caballero. Conversely, if it doesn’t have one, the other planets in orbit won’t either.

These are more difficult to detect: as they are farther from their star, they pass in front less often. Hence the need to “start somewhere”.

“Gliese 486 b is an exceptional discovery, which will probably become the + Rosetta stone + of atmospheric research of rocky exoplanets”, summarizes Trifon Trifonov.

He is eagerly awaiting the deployment of the much-anticipated James Webb Space Telescope, which is due to launch this year. Thanks to him, it would be possible, in at best about 3 years, to say whether or not this exoplanet has an atmosphere, and to give its composition.

Then, perhaps, “in a decade or two”, to detect traces of life on one of his binoculars, dreams José A. Caballero.

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