K2-22b (also known as EPIC 201637175 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 ...

801 ly 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 ...

, rapidly orbiting the

red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...

K2-22 with an orbital period of 9.145872 hours. It has a mass of and a radius below . The planet was not detected in the K2

photometry Photometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an astronomical object's electr ...

. K2 photometry reveals the presence of an anomalous light curve consistent with evaporation of dust from the planet. This dust forms a tail both ahead and behind the planet, similar to some comets in the Solar System. The evaporation of this dust requires a low surface gravity from the host planet, implying it is a low mass, "Mars, Mercury, or even lunar sized bodies with surface gravities of 1/6 to 1/3 that of

are to be preferred." The survey in 2020 has failed to validate the existence of the planet, although did not claim it to be a false positive. The observation of planetary system in 2021 has failed to detect the planet itself, placing an upper limit of 0.71 on its size. With the observed mass loss rate, the probable planet mass is 0.02, and the planet will be gone in 21 million years in future. Ground-based observations detected the transits in 2016/2017.

Faulkes Telescope North The Faulkes Telescope North is a clone of the Liverpool Telescope, and is located at Haleakala Observatory in the U.S. state of Hawaii. It is a f/10 Ritchey-Chrétien telescope. The telescope is owned and operated by LCOGT. This telescope an ...

/MuSCAT observations detected 7 predicted transits in 2021/2022. This observation showed a decline of transit depth since discovery. This could be due to a magnetic cycle of the host star, or the overturn of the

magma ocean Magma oceans are vast fields of surface magma that exist during periods of a planet's or some natural satellite's accretion when the celestial body is completely or partly molten. In the early Solar System, magma oceans were formed by the melt ...

. This could mean that the transit activity will increase again in the future. In April 2024 the evaporated material was observed with JWST

MIRI Miri () is a coastal city in north-eastern Sarawak, Malaysia, located near the border of Brunei, on the island of Borneo. The city covers an area of , located northeast of Kuching and southwest of Kota Kinabalu. Miri is the second largest ...

transmission spectroscopy Absorption spectroscopy is spectroscopy that involves techniques that measure the absorption of electromagnetic radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, ...

. The observation was done using low-resolution

slitless spectroscopy Slitless spectroscopy is spectroscopy done without a small slit to allow only light from a small region to be diffracted. It works best in sparsely populated fields, as it spreads each point source out into its spectrum, and crowded fields can be t ...

to observe four transits. The transit depth varies over time between 0% and 1.3%, so not every transit was detected. One transit was detected with high significance and two others were detected with low significance. The researchers also observed the transits with

CHEOPS Khufu or Cheops (died 2566 BC) was an ancient Egyptian monarch who was the second pharaoh of the Fourth Dynasty, in the first half of the Old Kingdom period (26th century BC). Khufu succeeded his father Sneferu as king. He is generally accep ...

. Only the 4th and most significant transit was unobstructed by the earth. The data is consistent with some kind of magnesium silicate minerals. Earth's mantle is rich in

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

-rich silicates, with relative little

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

. The evaporating minerals could condense into

enstatite Enstatite is a mineral; the magnesium endmember of the pyroxene silicate mineral series enstatite (MgSiO3) – ferrosilite (FeSiO3). The magnesium rich members of the solid solution series are common rock-forming minerals found in igneous and m ...

(MgSiO₃) or

forsterite Forsterite (Mg2SiO4; commonly abbreviated as Fo; also known as white olivine) is the magnesium-rich Endmember, end-member of the olivine solid solution series. It is Isomorphism (crystallography), isomorphous with the iron-rich end-member, fayalit ...

(Mg₂SiO₄). An earlier work did however find that the modelling of the transits agree with magnesium-iron silicates (

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

and

pyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...

). While the single JWST spectrum cannot distinguish between minerals, it can at least exclude iron-rich

planetary core A planetary core consists of the innermost layers of a planet. Cores may be entirely liquid, or a mixture of solid and liquid layers as is the case in the Earth. In the Solar System, core sizes range from about 20% (the Moon) to 85% of a plan ...

material. The spectrum also shows an unexpected feature at 5 μm, which could be the from gases, possibly NO or CO₂. The origin of these gases is not clear and additional observations are needed to confirm this signal. Two geophysical scenarios are suggested. In one situation the gases originate from an evaporating

deep ocean The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low tempe ...

, containing

clathrate hydrate Clathrate hydrates, or gas hydrates, clathrates, or hydrates, are crystalline water-based solids physically resembling ice, in which small non-polar molecules (typically gases) or polar molecules with large hydrophobic moieties are trapped ins ...

s of N₂, NH₃ and CO₂. In the other situation the molecules N₂, CO₂, and H₂O degas from a

. Some of these gases are then turned into NO by

photodissociation Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by absorption of light or photons. It is defined as the interaction of one or more photons wi ...

, collisional dissociation, or gas-phase chemistry.

References

{{2015 in space Exoplanets discovered in 2015 Transiting exoplanets 2 Leo (constellation) Sub-Earth exoplanets Ultra-short period planets

See also

References