Astronomers believe that this will help to trace the evolution of the atmospheres themselves, as well as understand under what conditions such unusual exoplanets are formed.
Astronomers have confirmed the discovery of two new exoplanets with ultrashort orbital periods. Both exoplanets belong to the class of super-earths, and one of them has become one of the largest and most massive bodies among exoplanets, the year on which lasts less than one earthly day.
Super-Earths can help solve the mysteries of the evolution of hot atmospheres
Ultrashort orbital periods
Exoplanets with an ultrashort period include planets whose orbital period is less than one Earth day. Usually, these are objects with a radius of less than two Earth radii, today more than a hundred such planets are known, they are often found in multiplanetary systems.
Host stars
It is believed that the frequency of their appearance may be related to the spectral type of the host star, in particular, they are found in red dwarfs of type M much more often than in yellow-white dwarfs of type F. The origin of such bodies remains the subject of controversy, most often scenarios for the migration of planets through the system are proposed, and not their initial formation near the star.
More observations are needed
To confirm, refute or refine the existing models, scientists need new cases of observations of exoplanets with ultrashort periods, where the masses and radii of objects are determined with great accuracy.
Two new Super-Earths
A group of astronomers led by Teruyuki Hirano from the National Astronomical Observatory of Japan announced confirmation of the discovery of two new exoplanets with ultrashort periods. Initially, they were found by the transit method using the TESS space telescope in 2019, later several ground-based telescopes, including the Keck telescopes, Subaru and Gemini North, observed the exoplanets.
Locations
Both exoplanets are located in star systems in the constellation Perseus at distances of 114 and 122 light-years from the Sun, they revolve around red dwarfs with a mass of 0.45-0.46 solar masses and a radius of 0.45-0.46 solar radius.
Mass and radius
The mass of TOI-1634b was 10.14 Earth masses while its radius was 1.749 when compared to Earth. In turn, TOI-1685b has 3.43 Earth masses and 1.459 Earth’s radius, respectively. Both exoplanets were classified as super-earths and have an average density corresponding to the internal composition of the Earth, which is typical for small planets with an ultrashort period. The year on TOI-1634b is 0.98 Earth days, and on TOI-1685b it is 0.669 days.
TOI-1634b
TOI-1634b’s properties make it one of the largest and most massive ultrashort-period exoplanets, which can help determine the size limit for rocky exoplanet nuclei, as well as test models for the formation of ultrashort-period planets.
Suitable targets for future studies
Both planets are included in the list of the most suitable targets for future spectroscopic studies of their possible atmospheres, including with the help of the James Webb telescope.
Evolution of hot atmospheres
Astronomers believe that this will help to trace the evolution of the atmospheres themselves, as well as understand under what conditions such unusual exoplanets are formed.
Speculations
Astronomers speculate that the atmosphere on such planets can be formed from gases born in their bowels and being blown out. However, the influence of the tidal forces of closely spaced stars is so great that the thin gaseous envelope does not have time to gain density and volume, but breaks apart and is carried away in pieces into open interstellar space.
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Sources:
• Hirano, T. (n.d.). Two Bright M Dwarfs Hosting Ultra-Short-Period Super-Earths with Earth-like Compositions.
• Phys.org. (2021, September 27). ‘Bare’ super-earths offer clues to evolution of hot Atmospheres.
• Subaru Telescope. (n.d.). “Bare” Super-Earths Offer Clues to Evolution of Hot Atmospheres: Obsevation results.
