(Patricia Klein / SPP 1992)
Astronomers have discovered a new sub-earth with an ultrashort period.
The exoplanet, named GJ 367b, revolves around a red dwarf and with a size comparable to Mars, it can have a huge iron core, so its structure is more like that of Mercury.
Exoplanets with an ultrashort period are characterized by an orbital period of less than one Earth day.
Most often these are small (less than two terrestrial) planets, the origin of which is still the subject of controversy among astronomers.
In particular, it is believed that such objects could have formed as a result of the migration of planets through the system, and not the initial formation near the star, and may be the cores of mini-neptunes.
To understand which theoretical models of the formation and evolution of such planets are correct, scientists need a large amount of observational data on exoplanets with ultrashort periods, giving accurate values of their masses and radii.
Now, a group of astronomers led by Kristine W. F. Lam from the Institute for Planetary Research at the German Aerospace Center announced the discovery of a new ultrashort-period exoplanet, GJ 367b, classified as a sub-earth.
The planet was originally discovered in 2019 by the TESS space telescope using the transit photometry method.
Then, the HARPS spectrograph installed on the 3.6-meter telescope at La Silla Observatory helped confirm the discovery and determine the main properties of the exoplanet using the method of radial velocities.
The parent star GJ 367b is a bright red dwarf with a mass of 0.45 solar masses, a radius of 0.45 solar radius and a luminosity of only 0.028 solar luminosity. It is located 31 light years from Earth.
Around the star, with a period of 7.7 hours, an exoplanet revolves with a radius of 0.718 of the Earth's radius and a mass of 0.546 of the Earth's mass.
This gives a value for the planet's bulk density of 8.106 grams per cubic centimeter, which is close to the density of iron.
The temperature on the daytime side of the planet is estimated at 1745 Kelvin, which implies the evaporation of any primary atmosphere.
Scientists have concluded that the properties of GJ 367b are best described by a model in which the planet consists of an iron core, with a radius of 86% of the radius of the planet
The planet should have also a shell of water ice and/or hydrogen and helium, which accounts for 10% of its radius and silicate mantle.
Thus, the planet, with dimensions comparable to Mars, has a structure similar to Mercury.
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