Astronomers have discovered a rocky Earth-sized world, or “super-Earth”, that is hot enough to melt gold and, therefore, may not have an atmosphere.
By comparing these super-Earths to our planet, scientists can identify which of these terrestrial exoplanets might be able to host life.
“We are just beginning to know how often and under what circumstances, rocky planets can retain their atmospheres,” said Laura Kreidberg, an exoplanet scientist at the Max Planck Institute for Astronomy in Germany and co-author of a new paper describing the discovery. statement (opens in a new tab). “This measurement is an indication that for the hottest planets, thick atmospheres are unlikely to generally survive.”
The exoplanet, called GJ 1252 b, is located 65 light years away. It is much closer to its star than Earth is at the Sunand one side – its “day side” – permanently faces its star, driving up temperatures on the exoplanet.
Related: Super-Earths are more common and more habitable than Earth. Astronomers find more than billions there.
When astronomers used the now-retired Spitzer Space Telescope to measure infrared radiation from GJ 1252 b as exoplanet passed behind its star – an arrangement called a “secondary eclipse” – they discovered that the planet’s daytime temperatures reached 2,242 degrees Fahrenheit (1,228 degrees Celsius).
Not only are these temperatures so high that gold, silver and copper would melt on the planet’s surface, but this extreme heat would prevent GJ 1252 b from clinging to a thick atmosphere. The team thinks this scorching temperature is consistent with what one would expect for a planet with a bare, rocky surface.
Additionally, the team found that GJ 1252 has a surface pressure of no more than 10 bar, indicating that its atmosphere – if it exists – must be noticeably thinner than that of Venus.
Astronomers have calculated that on GJ 1252 b, a uniform atmosphere thick enough to cause a surface pressure 10 times greater than this would have been removed from the planet in a million years – much shorter than the duration exoplanet’s estimated lifetime of 3.9 billion years.
As such, GJ 1252 has an extremely limited atmosphere or possibly no atmosphere at all, the team concluded in their paper, which was published Sept. 23 in The Astrophysical Journal Letters.
It’s the smallest planet to date for which scientists have determined strict atmospheric constraints, said Ian Crossfield, a University of Kansas astronomer who led the research.
Further investigation of GJ 1252 b with the James Webb Space Telescope (JWST) could place even tighter constraints on the planet’s atmosphere — or lack thereof — over the next few years.
“At the time, Spitzer was the only facility in the known universe that could do these kinds of measurements,” Crossfield said in the statement. “Now Spitzer has been turned off, but JWST is there, and at these wavelengths it’s much more sensitive than Spitzer was.”
This means that the type of work that Crossfield and his team did with Spitzer will be much easier with JWST.
“JWST observations in the infrared have the potential to reveal the surface properties of hot, rocky planets like this one,” Kreidberg said. “Different types of rock have different spectral signatures, so we could potentially know what type of rock GJ 1252b is made of.”
Further study of GJ 1252b could thus reveal the composition of the planet, and this investigation could be extended to many other terrestrial worlds like GJ 1252b, giving astronomers a better understanding of relatively small and hot exoplanets, the researchers said. .
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