TOI-849 b is an

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

orbiting the late-G type star TOI-849. It is a candidate

chthonian planet Chthonian planets (, sometimes 'cthonian') are a hypothetical class of celestial objects resulting from the stripping away of a gas giant's hydrogen and helium atmosphere and outer layers, which is called hydrodynamic escape. Such atmospheric ...

, the exposed core of a gas giant that had much of its atmosphere stripped away. It is around 700 light-years away from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

Characteristics

TOI-849 b is a high-density planet more massive than Neptune, about forty times the mass of Earth. It orbits very close to its host star, with a period of less than one day, placing it within the Neptunian desert. Compared to other Neptune-sized exoplanets, this planet is unusually massive and dense. It is about 40 times the mass of Earth, but only about 3.4 times Earth's radius. This implies that any gaseous envelope of

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

and

helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...

makes up at most percent of the planet's mass. However, given the planet's size, its density is still too low for a purely rocky composition. The gravity of such a massive planet would be expected to accrete large amounts of gas from the

protoplanetary disk A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion disk; while the two are sim ...

in which it formed, causing it to become a

gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranu ...

. It is thought that TOI-849 b could be the remnant core of a gas giant. A 2021 modeling study found that the stellar radiation received by the planet could have removed the entire gaseous envelope even if it formed as a Jupiter-mass planet.

References

{{Fornax Exoplanets discovered in 2020 Exoplanets discovered by TESS Transiting exoplanets