Wobbling stars reveal their hidden companions

Using data from the Gaia mission, scientists have detected wobbles in two low-mass stars. They are caused by a huge gas giant and a brown dwarf orbiting around them.

From wobbles to new worlds

If an exoplanet is orbiting around a star, its gravitational influence will cause the star itself to “wobble” around its center of mass, and its motion across the sky will be “corkscrew-like”. The method of detecting exoplanets from such deviations is called astrometry. It is best suited for searching for massive objects in distant orbits around its parent star.

Deviations in the position of a star caused by the effects of the gravity of its massive companion. Source: ESA

Despite a number of potential advantages, astrometry has not been very popular with astronomers until recently. The fact is that changes in the positions of stars are so small, and atmospheric and systematic distortions so great, that even the best ground-based telescopes cannot make quite accurate measurements.

That all changed thanks to the Gaia mission. Since its launch in 2013, the space observatory has been creating the largest and most accurate three-dimensional map of our galaxy. It repeatedly scanned the sky, determining the position of two billion Milky Way objects with unprecedented accuracy. Analyzing Gaia data has already allowed astronomers to find several brown dwarfs, whose existence was confirmed during subsequent observations. Now the telescope has managed to record an exoplanet on its account.

Two mysterious celestial bodies

The discovery was made while analyzing data from Gaia’s third release, published in 2022. Astronomers have managed to confirm the existence of two mysterious celestial bodies, designated Gaia-4b and Gaia-5b.

Gaia-4b and Gaia-5b in an artist’s impression. Source: ESA/Gaia/DPAC/M. Marcussen

Gaia-4b is a so-called super Jupiter. It is a relatively cold gas giant located at a distance of 244 light-years from Earth. It is about 12 times more massive than Jupiter, and its orbital period around the star is 570 days.

As for Gaia-5b, it is a brown dwarf. It is located at a distance of 134 light-years from Earth, its mass is 21 times that of Jupiter. Such objects are sometimes called failed stars. They may have some thermonuclear reactions in their interior, but they never ignite as full-fledged stars.

Both Gaia-4b and Gaia-5b orbit low-mass red dwarfs, which is considered an extremely rare scenario. According to astronomers, the finding has the potential to challenge existing theories of planet formation. They hope that the new release of Gaia data will reveal more exoplanets and brown dwarfs, which will help to clarify the picture and better understand the structure of planetary systems.

According to ESA

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