Teegarden's Star b (also known as Teegarden 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 ...

found orbiting within the habitable zone of

Teegarden's Star Teegarden's Star (''SO J025300.5+165258'', ''2MASS J02530084+1652532'', ''LSPM J0253+1652'') is an stellar classification, M-type red dwarf star in the constellation Aries (constellation), Aries, from the Solar System. Although it is L ...

, an M-type

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 ...

12.5 light years away from the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

. It had the highest

Earth Similarity Index The Earth Similarity Index (ESI) is a proposed characterization of how similar a planetary-mass object or natural satellite is to Earth. It was designed to be a scale from zero to one, with Earth having a value of one; this is meant to simplify p ...

(ESI) of any exoplanet, but in February 2024 a new study updated the parameters of the planet, thus reducing its ESI to , making it no longer the planet with the hightest ESI. Along with

Teegarden's Star c Teegarden's Star c (also known as Teegarden c) is an exoplanet found orbiting in the habitable zone of Teegarden's Star, an M-type red dwarf star 12.5 light years away from the Solar System. It orbits in the conservative habitable zone around its ...

, it is among the closest known potentially habitable exoplanets.

Discovery

In July 2019, a team of more than 150 scientists led by Mathias Zechmeister published a peer-reviewed article in

Astronomy & Astrophysics ''Astronomy & Astrophysics (A&A)'' is a monthly peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics. It is operated by an editorial team under the supervision of a board of directors re ...

as part of the CARMENES survey supporting the existence of two candidate exoplanets orbiting Teegarden's Star. Because of the alignment and faintness of Teegarden's Star,

Doppler spectroscopy Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in ...

(also known as the radial velocity method) was necessary to detect possible exoplanets. This method detects exoplanets indirectly by observing their effects on a host star's

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

, the speed at which it is moving towards or away from the Earth. These radial velocity anomalies in turn produce

doppler shift The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. The ''Doppler effect'' is named after the physicist Christian Doppler, who described t ...

s observable with a

spectrograph An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...

-equipped telescope of sufficient power. To accomplish this, the team used the CARMENES instrument on the telescope of Spain's

Calar Alto Observatory The Calar Alto Observatory (Centro Astronómico Hispano en Andalucía or "Spanish Astronomical Centre in Andalusia") is an astronomical observatory located in Almería province in Spain on Calar Alto, a mountain in the Sierra de Los Filabre ...

. After three years of observation, two periodic radial velocity signals emerged: one at (Teegarden's Star b) and another at (

Physical characteristics

Mass and orbit

Teegarden's Star b is the innermost known planet orbiting Teegarden's Star, with an orbital period of just . The planet's

minimum mass In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars, binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets detected by the radial velocit ...

is ; this value would be the true mass if the planet's orbit is not inclined from the Earth's perspective. Because of this, Teegarden's Star b is likely to be rocky. Astronomers estimate that Teegarden's Star b has a 60 percent chance of having liquid water, but only a 3 percent chance of having an atmosphere.

Host star

Teegarden’s Star is a low-mass red dwarf, with a mass of around 9 percent the mass of the Sun, and with a temperature of around . Due to the very low temperature and luminosity of Teegarden's Star, it was only discovered in 2003, since it has an apparent magnitude of only 15.1 (and an absolute magnitude of 17.22). Like most red and brown dwarfs, it emits most of its energy in the infrared spectrum. It is also older than the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, with an age of at least 8 billion years.

Habitability

Teegarden's Star b orbits within the habitable zone of its host star, meaning it is possible that its atmospheric composition could allow for stable liquid water on its surface, which could have also allowed the development of life.

References