COCONUTS-2 b is 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 ...

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 ...

that orbits the

M-type star In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

L 34-26. With a mass of 8 Jupiters, it takes over one million years to complete one orbit around the star orbiting 7,506 AU away from it. The planet was discovered in 2011 and was initially identified as a T9 free-floating

brown dwarf Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...

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 closes ...

(COCONUTS) survey, its association with L 34-26 was announced in 2021. At a distance of , COCONUTS-2b was the closest directly imaged exoplanet to Earth until

Epsilon Indi Ab Epsilon Indi Ab is a gas giant exoplanet orbiting the star Epsilon Indi A, about 11.9 light-years away in the constellation of Indus. The planet was confirmed to exist in 2018. It orbits at around 30 AU (almost as far as Neptune from the Sun) ...

was imaged in 2024.

Proposed formation scenarios

The researchers found that it is unlikely that COCONUTS-2b was formed inside 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 ...

of the host star and may instead have formed separately. The peculiar properties of COCONUTS-2b could be explained with different scenarios as proposed by Marocco et al. in 2024. The properties could be explained by a non-solar

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

-to-

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

ratio, meaning that it formed inside a disk around L 34–26. In this scenario the most likely way COCONUTS-2b got in a higher orbit is by a stellar fly-by of two binaries or two planetary systems. In the second scenario L 34-26 is not actually young, but mimics youth due to tidal and/or magnetic interactions with an unseen companion. In this scenario COCONUTS-2b would be an old brown dwarf. In a third scenario COCONUTS-2b could be a captured old brown dwarf. This is however seen as unlikely due to the stellar fly-by requiring a low velocity. Another study in 2024 found that the

metallicity In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...

of the planet is lower than that of the host star, which is inconsistent with it forming on its current location, like a

binary system A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.) The most common ki ...

. Only their third-preferred model is consistent with a binary-like formation, because in this model the metallicity of host star and planet agreed.

Atmosphere

The planet's

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

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 abundance of methane on Earth makes ...

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

and low amounts of

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

in the

atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

of COCONUTS-2b. It might also have both

cloud 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 ...

s 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 . Observations with

Gemini Gemini most often refers to: * Gemini (constellation), one of the constellations of the zodiac * Gemini (astrology), an astrological sign Gemini may also refer to: Science and technology Space * Gemini in Chinese astronomy, the Gemini constellat ...

/Flamingos-2 showed a spectral type of T, near the T/ Y transition. The spectrum is also more consistent with disequilibrium chemistry and the presence of clouds. Additionally the atmosphere shows a diabatic thermal structure, meaning the pressure-temperature profile is non- adiabatic. Adiabatic means here an increase of the temperature with

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

. The observation also indicate a sub- or near-solar

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 from Earth, in the constellation of

Chamaeleon Chamaeleon () is a small constellation in the deep southern sky. It is named after the chameleon, a kind of lizard. It was first defined in the 16th century. History Chamaeleon was one of twelve constellations created by Petrus Plancius f ...

. The star is about one-third the mass of the Sun, with an age between 150 and 800 million years old. Researchers using

TESS Tess or TESS may refer to: Film and theatre * Tess (1979 film), ''Tess'' (1979 film), a 1979 film adaptation of ''Tess of the d'Urbervilles'' * Tess (2016 film), ''Tess'' (2016 film), a South African production Music * Tess (band), a Spanish pop ...

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. The star is seen almost equator-on with i = 81.8±5.8 deg and might belong to the proposed Ursa Major corona, which is 400 million years old.

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

External links

{{Stars of Chamaeleon Exoplanets discovered in 2021 Exoplanets detected by direct imaging Gas giants Chamaeleon