Giant rocky planet discovered 36 light-years from Earth

(ORDO NEWS) — An international team of astronomers has announced the discovery of a new super-Earth exoplanet orbiting the red dwarf Ross 508.

The giant rocky planet, designated Ross 508 b, is four times more massive than Earth and is 36.5 light-years away. The discovery is described in detail in a preprint published in the arXiv repository.

The researchers conducted spectrometric observations of the red dwarf Ross 508 using the InfraRed Doppler instrument on the Subaru telescope, which made it possible to measure the radial velocity of the star.

The radial velocity is determined for a space object that moves relative to the observer’s line of sight and is thus subject to the Doppler effect. In the case of a star, the reason for the non-zero radial velocity is a massive celestial body rotating around it – for example, a planet.

Astronomers have identified a periodicity of radial velocity oscillations of a star of 10.75 days, which corresponds to the orbit of the planet, which has four times the mass of the Earth and is 0.053 astronomical units away from the parent star (one astronomical unit is equal to the average distance from the Sun to the Earth).

Ross 508 b should receive 1.4 times as much sunlight as Earth, placing the planet at the inner edge of the habitable zone.

The exact orbital eccentricity of Ross 508 b is still unknown. It is assumed that the super-Earth was originally formed outside the snow line, where the water passes into a solid state of aggregation. For Ross 508, this distance is about 0.16 astronomical units.

The planet then underwent Type I migration, where density waves in the gas of the protoplanetary disk push the celestial body closer to the star. Even if the eccentricity of the planet’s orbit was initially quite high, density waves could reduce it significantly, making the orbit more rounded and less elongated.

The parent star Ross 508 has a radius of about 0.21 solar radii and a mass of about 0.18 solar masses, corresponding to a density of 26.5 grams per cubic centimeter. The star has an effective temperature of 3071 K, and the abundance of heavy elements is 100 times less than that of the Sun. It is 36.5 light years away from Earth.

Super-Earths are giant rocky planets that are more massive than Earth, but do not exceed the mass of Neptune.

Although the term “super-Earth” is usually applied to planetary masses, it is also used by astronomers to describe planets larger than Earth but smaller than mini-Neptunes, with a radius of two to four Earth radii.


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