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LHS 3844b, a 1.3 Earth-ray terrestrial world in an 11-hour orbit around the nearby small star LHS 3844, most likely has little or no atmosphere and could be covered with the same cooled volcanic material that includes the Dark lunar regions known as the mare, according to new research.
The artistic conception of a terrestrial exoplanet, LHS 3844b, which gravitates around a small star at 49 light-years from Earth. Image credit: NASA / JPL-Caltech / R. Hurt, IPAC.
Discovered in 2018 by NASA's TESS mission, the LHS 3844b is located approximately 49 light-years from Earth.
The planet has a radius of 1.3 times that of the Earth and gravitates around a small type of cool star called Dwarf M (red dwarf).
The LHS 3844b is most likely "locked by the tides", with one side of the planet constantly facing the star. The side facing the star, or day side, is about 710 degrees Celsius (1410 degrees Fahrenheit).
TESS has detected the LHS 3844b via the transit method, which detects when the observed light of the parent star is attenuated when its exoplanet in orbit crosses the line of sight between the star and the Earth.
In follow-up observations, the IRAC camera on board NASA's Spitzer Space Telescope was able to detect infrared light on the surface of the LHS 3844b.
By measuring the difference in temperature between the hot and cold sides of the planet, astronomers concluded that a negligible amount of heat was transferred between the two.
If an atmosphere were present, the warm daylight air would naturally expand, generating winds that would transfer heat around the planet.
"The temperature contrast on this planet is about as big as possible. It's a perfect match for our atmospheric rock model, "said Dr. Laura Kreidberg, lead author, researcher at the Harvard & Smithsonian Center for Astrophysics.
Spitzer's observations exclude an atmosphere with a pressure more than 10 times greater than that of the Earth (measured in units called bars, the atmospheric pressure at the level of the sea of the Earth is about 1 bar).
An atmosphere between 1 and 10 bar on the LHS 3844b has been almost completely ruled out, although it has a low chance of existing if the stellar and planetary properties were to meet very specific and improbable criteria.
"We have had a lot of theories about how the planetary atmospheres are around the M dwarfs, but we have not been able to study them empirically," said Dr. Kreidberg.
"Now, with LHS 3844b, we have a terrestrial planet outside our solar system where, for the first time, we can determine observatively that an atmosphere is not present."
The study was published online this week in the journal Nature.
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Laura Kreidberg et al. Absence of thick atmosphere on the Earth's exoplanet LHS 3844b. Nature, published online 19 August 2019; doi: 10.1038 / s41586-019-1497-4
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