Astronomers have found a giant star preparing to swallow its planet

(ORDO NEWS) — Astronomers have discovered a new warm Jupiter, HD 167768b, around an old evolved giant star. It is expected that in the next 150 million years, the expanding star will swallow the exoplanet.

As low- and medium-mass stars age, they go through the stage of transformation into a giant or supergiant and eventually lose their outer shell.

More than 150 exoplanets have been discovered around stars that have evolved in this way over the past 20 years, and among them there are very few short-period objects in which the semi-major axis of the orbit is less than 0.6 astronomical units.

This can be explained both by the properties of the protoplanetary disk at the time of the formation of the planets, and by the influence of the parent star at a late stage of evolution – it can destroy the planet with tidal forces or even swallow it.

A third option is also possible – this is just a feature of the current sample of known planets.

A team of astronomers led by Huan-Yu Teng of the Tokyo Institute of Technology announced the discovery of a new exogiant in the highly evolved sun-like star HD 167768.

The discovery was made using the radial velocity method using the HIDES echelle spectrograph mounted on a 188 cm telescope at the Okayama Astrophysical Observatory.

HD 167768 is 5.3 billion years old. The star belongs to the spectral class G8 III and has a mass of 1.08 solar masses, and ten times the size of our star. Its effective temperature is 4851 Kelvin.

A planet revolves around the star with a minimum mass of 0.85 Jupiter masses, which is characterized by an equilibrium temperature of 1874 kelvin, which makes it possible to attribute it to warm Jupiters.

It is in a very compact orbit around the star – an orbital period of 20.65 Earth days. The semi-major axis of the orbit has a length of 0.151 astronomical units, and the eccentricity is 0.149.

Scientists have come to the conclusion that the star continues its evolution, so it will move further along the red giant branch and expand.

In the near future, this will lead to the death of the exoplanet. HD 167768 is expected to engulf its warm Jupiter in 150 million years.

Astronomers have found a giant star preparing to swallow its planet
Time evolution of the planet’s semi-major axis (solid line) and stellar radius (dashed line)


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