The scorching ‘super-Earth’ may have lost its atmosphere
Astronomers have discovered a rocky Earth-sized world, or “super-Earth,” that’s hot enough to melt gold and, as a result, may have no atmosphere.
By comparing these super-Earths to our planet, scientists can identify which of these terrestrial exoplanets may be capable of hosting life.
“We are just beginning to learn how often and under what circumstances, rocky planets can maintain 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, in a statement (opens in a new tab). “This measurement is an indication that, for hotter planets, thick atmospheres are unlikely to normally survive.”
The exoplanet, called GJ 1252 b, is 65 light-years away. It is much closer to its star than land is at groundand one side, its “dayside,” permanently faces its star, raising temperatures on the exoplanet.
When astronomers used the now retired Spitzer Space Telescope to measure the infrared radiation from GJ 1252 b as a 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 hot that gold, silver, and copper would melt on the planet’s surface, but this extreme heat would make it difficult for GJ 1252 b to cling to a thick atmosphere. The team believes this scorching temperature is consistent with what would be expected for a planet with a bare, rocky surface.
In addition, the team found that GJ 1252 b has a surface pressure of no more than 10 bar, indicating that its atmosphere, if it exists, must be substantially thinner than that of Venus.
Astronomers calculated that at GJ 1252 b, a uniform atmosphere thick enough to cause a surface pressure 10 times that would have been stripped from the planet over the course of a million years, much shorter than the estimated lifetime of the 3.9 billion year old exoplanet. .
As such, GJ 1252 b has an extremely limited or possibly no atmosphere, the team concluded in their paper, which was published Sept. 23 in The Astrophysical Journal Letters.
This is the smallest planet yet for which scientists have determined tight atmospheric constraints, said Ian Crossfield, the 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, for years to come.
“At the time, Spitzer was the only facility in the known universe that could make 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.”
That means the kind of work Crossfield and his team did with Spitzer will be much easier with JWST.
“JWST’s infrared observations have the potential to reveal the surface properties of hot, rocky planets like this one,” Kreidberg said. “Different rock types have different spectral signatures, so we could learn what kind of rock GJ 1252b is made of.”
Further study of GJ 1252b could thus reveal the planet’s composition, and this research could be extended to many more terrestrial worlds like GJ 1252b, giving astronomers a better understanding of relatively small and hot exoplanets, the researchers said.
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