NASA explores rocky exoplanet's surface

22 Août, 2019, 11:27 | Auteur: Therese Cote
  • This artist’s illustration shows LHS 3844b a rocky nearby exoplanet. It’s 1.3 times the mass of Earth and orbits a cool M-dwarf star

By measuring the heat coming from a planet almost 49 light-years away, astronomers were able to glean some information about the surface of the rocky world-a rare feat in exoplanet science.

Exoplanet LHS 3844b turned out to be a dead stone.

Scientists from the Harvard Center for Astrophysics used NASA's Transiting Exoplanet Satellite Survey (TESS) telescope to spot planet LTT 1445 A b and its three stars.

As expected, Spitzer's data shows that the planet's dark surface is probably covered in volcanic basalt or magma, or cooled volcanic material, likely from ancient volcano activity. "The planet also is the second closest discovered so far that "transits" its star - that is, the orbit of LTT 1445 AB is tilted at the correct angle to, from our vantage point, pass across the face of the star". The star-facing side of LHS 3844 b reaches temperatures of about 1,410 degrees Fahrenheit (770 degrees Celsius), while the nightside stays at about minus 459 degrees Fahrenheit (minus 273 degrees Celsius), as reported by Scientific American.

According to computer simulations, such a contrast in temperatures on LHS 3844 b means that the planet could only have an atmosphere of about one-tenth the pressure on Earth But in the environment of a red dwarf star, which pumps out high levels of ultraviolet radiation and frequent flares, such a thin atmosphere would nearly certainly be blown away, according to NASA. If LHS 3844b still has an atmosphere, that does not exceed the density of the Martian, which is extremely unexpected for a planet of this size. Though the parent star is cool, it is still comparatively much hotter than the planet, so making direct observation of LHS 3844b's dayside possible.

The team measured the temperature difference between the exoplanet's hot and cold sides and determined that there is an insignificant amount of heat being transferred between the two. But if an atmosphere were present, it would allow for the force of wind to carry hot air to the other side of the planet.

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Dubbed LHS 3844b, the planet has no atmosphere but holds to key to understanding where scientists should be looking for signs on life beyond Earth.

Following this observation, Spitzer was able to provide details on the atmosphere of a terrestrial world orbiting an M dwarf, according to NASA.

The presence of an atmosphere on the Earth is the reason liquid water can exist on the surface, enabling life on the planet. On the other hand, the atmospheric pressure of Mars is now less than 1% of Earth's, and the oceans and rivers that once dotted the Red Planet's surface have disappeared.

"Now, with LHS 3844b, we have a terrestrial planet outside our solar system where for the first time we can determine observationally that an atmosphere is not present", explains Kriedberg. They're particularly violent in their youth, belching up a large number of flares, or bursts of radiation and particles that could strip away budding planetary atmospheres. And in this case, the planet is so close to the star that the stellar wind coming off it would probably do away with the atmosphere.

Exceptional yet common Red dwarves themselves aren't uncommon as the smallest and the coolest of the star categories.

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