Illustration of exoplanet Gliese 486b
Astronomers have discovered a planet on which the atmospheres of Earth-like worlds can be examined.
Gliese 486b orbits a red dwarf star only 26 light years away and presumably resembles Venus, reports an international team of researchers in the journal Science.
Its short distance from Earth, its temperature and the orientation of its orbit make the exoplanet an ideal candidate for observations with future large telescopes.
Astronomers have now discovered over 4,600 planets in other stars.
These include many rock planets that resemble the inner planets of our solar system, i.e. Mercury, Venus, Earth and Mars.
Some of these distant planets orbit in the life-friendly zone around their central star, i.e. where temperatures are moderate and liquid water is possible on the surface.
Looking for staggering stars
For such planets, researchers are developing atmospheric models in order to better assess whether there could actually be life there.
The problem: The scientists have not yet been able to check their models because too little is known about the distant worlds.
Gliese 486b could be a first step to change that.
"The discovery of Gliese 486b is a stroke of luck," says co-author José Caballero from the Center for Astrobiology in Madrid.
“A hundred degrees hotter and the entire surface would be lava - its atmosphere would be vaporized rock.
If Gliese 486b were a hundred degrees colder, on the other hand, it would be unsuitable for follow-up observations. ”Because then the planet's atmosphere would emit too little radiation for an investigation.
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Astronomers use two methods in particular to find planets in other stars: On the one hand, they look for slight staggering movements of stars, which in turn is triggered by the gravitational pull of planets.
On the other hand, the researchers monitor the brightness of a large number of stars in search of regular fluctuations caused by planets passing in front of the stars.
Gliese 486b is one of the few planets that can be detected with both methods.
Therefore, astronomers were able to determine not only its orbit, but also its size and mass.
The planet orbits its small, red central star every day and a half in a very narrow orbit.
It has about 2.8 times the mass of the earth and is about 30 percent larger than our home planet.
Super Venus instead of Super Earth
From the size and mass of the planet, the researchers conclude that it has a similar structure to the earth, i.e. that it consists of rock with an iron core.
Astronomers call such massive rock planets super-earths, but Gliese 486b is more of a super-Venus with a surface temperature of around 426 degrees Celsius.
Although this heat is too great for the water to remain liquid, it offers the chance that Gliese 486b, like Venus, has a dense, easily observable atmosphere.
The astronomers could then use future instruments such as the James Webb Space Telescope from NASA and the Extremely Large Telescope from the European Southern Observatory (Eso) to measure what proportion of starlight is absorbed by the atmosphere and at what wavelengths it shines - and something like that about the composition and Experience the nature of the atmosphere.
"We can hardly wait until the new telescopes are available," says Trifon Trifonov from the Max Planck Institute for Astronomy in Heidelberg, who played a key role in the discovery of Gliese 486b.
"The results will help us to understand how well rocky planets can hold their atmospheres, what the gas envelopes are made of and how they influence the distribution of energy on the planet."
Icon: The mirror
jme / dpa