COCONUTS-2 b, or WISEPA J075108.79-763449.6, is a gas giant

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

that orbits the M-type star L 34-26. With a mass of 6.3

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, it takes over one million years to complete one orbit around the star, and it is 6000 AU away from it. The planet was discovered in 2011 and was initially identified as a T9 free-floating

brown dwarf Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...

WISEPA J075108.79−763449.6. During the

COol Companions ON Ultrawide orbiTS The COol Companions ON Ultrawide orbiTS (COCONUTS) program is a large-scale survey for wide-orbit planetary and substellar companions considered the first survey of this type of celestial bodies. In 2021, the team announced COCONUTS-2b, the closest ...

(COCONUTS) survey, its association with L 34-26 was announced in 2021. At a distance of 10.9 pc, COCONUTS-2b is the closest directly imaged exoplanet to Earth known to date. The researchers found that it is unlikely that COCONUTS-2b was formed inside the protoplanetary disk of the host star and it is more likely that the planet formed on its own via high

entropy Entropy is a scientific concept, as well as a measurable physical property, that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynam ...

formation (aka hot-start process).

Atmosphere

The planet has a spectral type of T9, based on a low

signal-to-noise Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in decib ...

near-infrared spectrum with Magellan/FIRE. This spectral type suggests high amounts of

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...

water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

and low amounts of

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

in the

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

of COCONUTS-2b. COCONUTS-2b might have both

clouds In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may com ...

and a non-equilibrium process in its atmosphere. Due to its large orbital separation, COCONUTS-2b is a great laboratory to study the atmosphere and composition of young gas-giant exoplanets. Astronomers estimate the planet’s temperature to be around .

Host star

L 34-26, also known as COCONUTS-2A and TYC 9381-1809-1, is a M3-type dwarf star located 35 light-years away, in the constellation of Chamaeleon. The star is about one-third the mass of the Sun, with an age between 150 and 800 million years old. Researchers using

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found that L 34-26 showed stellar flares about every 0.48 days. It was the most active planet hosting star in their sample. The team studying the host star also found that L 34-26 is fast rotating with a rotation period of 2.83 days. The planet should not be influenced by the flares, because of the large orbital separation.

Gallery

File:COCONUTS-2 system unWISE.png, The COCONUTS-2 system with unWISE File:COCONUTS-2b Gemini JHK.png, The planet COCONUTS-2b with Gemini-South File:COCONUTS-2b.jpg, Allwise image by the discoverers, showing planet COCONUTS-2b

References

{{2021 in space Exoplanets discovered in 2021 Exoplanets detected by direct imaging Gas giants