Teegarden's Star
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Teegarden's Star (''SO J025300.5+165258'', ''2MASS J02530084+1652532'', ''LSPM J0253+1652'') is 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 ...
star in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...
Aries Aries may refer to: *Aries (astrology), an astrological sign *Aries (constellation), a constellation in the zodiac Arts, entertainment and media * ''Aries'' (album), by Luis Miguel, 1993 * ''Aries'' (EP), by Alice Chater, 2020 * "Aries" (song), ...
, 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 ...
. Although it is near Earth it is a dim
magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...
15 and can only be seen through large telescopes. This star was found to have a very large
proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...
of about 5 arcseconds per year. Only seven stars with such large proper motions are currently known. Teegarden's Star hosts a
planetary system A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although ...
with at least three planets.


Discovery

Teegarden's Star was discovered in 2003 using
asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
-tracking data that had been collected years earlier. This data set is a digital archive created from optical images taken over a five-year period by the
Near-Earth Asteroid Tracking Near-Earth Asteroid Tracking (NEAT) was a program run by NASA and the Jet Propulsion Laboratory, surveying the sky for near-Earth objects. NEAT was conducted from December 1995 until April 2007, at GEODSS on Hawaii (Haleakala-NEAT; 566), as we ...
(NEAT) program using two 1 m telescopes on
Maui Maui (; Hawaiian language, Hawaiian: ) is the second largest island in the Hawaiian archipelago, at 727.2 square miles (1,883 km2). It is the List of islands of the United States by area, 17th-largest in the United States. Maui is one of ...
,
Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...
. The star is named after the discovery team leader, Bonnard J. Teegarden, an astrophysicist at
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
's
Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C., in Greenbelt, Maryland, United States. Established on May 1, 1959, as NASA's first space flight center, GSFC ...
. Astronomers have long thought it was quite likely that many undiscovered dwarf stars exist within 20 light-years of Earth, because stellar-population surveys show the count of known nearby dwarf stars to be lower than otherwise expected and these stars are dim and easily overlooked. Teegarden's team thought that these dim stars might be found by
data mining Data mining is the process of extracting and finding patterns in massive data sets involving methods at the intersection of machine learning, statistics, and database systems. Data mining is an interdisciplinary subfield of computer science and ...
some of the huge optical sky survey data sets taken by various programs for other purposes in previous years. So they reexamined the NEAT asteroid tracking data set and found this star. The star was then precovered on photographic plates from the
Palomar Sky Survey Palomar may refer to: Places * Any of several locations in San Diego County, California: ** Palomar Mountain *** Palomar Mountain, California, an unincorporated community ** Palomar College in San Marcos, California *** Palomar College Transit Ce ...
taken in 1951. This discovery is significant as the team did not have direct access to any telescopes and did not include professional astronomers at the time of the discovery.


Properties

Teegarden's Star is classified as a
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 ...
as its approximate calculated mass of just over 0.09 times that of the Sun is narrowly above the limit of
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 ...
s. The inherently low temperature of such objects explains why it was not discovered earlier, since it has an
apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...
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 Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
spectrum. The
parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...
was initially measured as 0.43 ± 0.13 arcseconds. This would have placed its distance at only 7.50
light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
s, making Teegarden's Star only the third star system in order of distance from 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 ...
, ranking between
Barnard's Star Barnard's Star is a small red dwarf star in the constellation of Ophiuchus. At a distance of from Earth, it is the fourth-nearest-known individual star to the Sun after the three components of the Alpha Centauri system, and is the c ...
and
Wolf 359 Wolf 359 is a red dwarf star located in the constellation Leo, near the ecliptic. At a distance of from Earth, it has an apparent magnitude of 13.54 and can only be seen with a large telescope. Wolf 359 is one of the nearest stars to ...
. However, even at that time the anomalously low luminosity (the absolute magnitude would have been 18.5) and high uncertainty in the parallax suggested that it was in fact somewhat farther away, still one of the Sun's nearest neighbors but not nearly as high in the ranking in order of distance. A more accurate parallax measurement of 0.2593 arcseconds was made by George Gatewood in 2009, yielding a distance of 12.578 light-years, very close to the value now accepted. Teegarden's Star is inactive compared to stars of similar spectrum and mass. It still shows some
stellar flare The asterisk ( ), from Late Latin , from Ancient Greek , , "little star", is a typographical symbol. It is so called because it resembles a conventional image of a heraldic star. Computer scientists and mathematicians often vocalize it as st ...
s with strengths comparable to the largest solar flares. Two of these flares were observed by a study, and one of them shows clear signatures of the
Neupert effect The Neupert effect refers to an empirical tendency for high-energy ('hard') X-ray emission to coincide temporally with the rate of rise of lower-energy ('soft') X-ray emission of a solar flare. Here 'hard' and 'soft' mean above and below an energy ...
.


Planetary system

Observations by the ROPS survey in 2010, published in 2012, showed variation in the
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 ...
of Teegarden's Star, though there was insufficient data to make claims of planet detection at that time. In June 2019, scientists conducting the CARMENES survey at the
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 ...
announced evidence of two Earth-mass exoplanets orbiting the star within its
habitable zone In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressu ...
; Teegarden's Star b orbits inside the optimistic habitable zone—the equivalent in the Solar System would be in between Earth and Venus—whereas
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 ...
orbits on the outer edge of the conservative habitable zone, similarly to Mars. A 2024 study detected a third planet orbiting farther out, with a period of 26 days and a
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 ...
slightly less than Earth's mass. This third planet, Teegarden's Star d, orbits beyond the habitable zone and would have temperatures similar to the icy
moons of Jupiter There are 97 Natural satellite, moons of Jupiter with confirmed orbits . This number does not include a number of meter-sized moonlets thought to be shed from the inner moons, nor hundreds of possible kilometer-sized outer irregular moons that ...
. Two longer-period
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 ...
signals were also detected; a 96-day signal corresponds to the star's rotation, while the origin of a 172-day signal is uncertain. According to one group of researchers, who were specifically studying this star, both habitable-zone planets could have maintained a dense atmosphere and so therefore there would be a high likelihood that at least one may harbour liquid water. However, another group of scientists, looking at Earth-sized planets in general in the habitable zones of stars, specifically in a likely
tidally locked Tidal locking between a pair of co-orbiting astronomical bodies occurs when one of the objects reaches a state where there is no longer any net change in its rotation rate over the course of a complete orbit. In the case where a tidally locked ...
scenario, give Teegarden's Star b a 3% chance, and Teegarden's Star c only a 2% chance, of having even retained an atmosphere. Teegarden's Star b, c and d receive more X-ray radiation than Earth does, but if they have certain atmospheric compositions, as an Earth-like atmosphere, the effects on the ground would still be negligible. While
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 ...
observations confirm that the planets of Teegarden's Star do not
transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1980 film), a 1980 Israeli film * ''Transit'' (1986 film), a Canadian short film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countrie ...
their star as seen from Earth, from 2044 to 2496 Earth would transit the Sun as seen from Teegarden's Star.


See also

* * * *


References


External links


SolStation.com

Image Teegarden's Star
{{DEFAULTSORT:Teegarden's Star Aries (constellation) Local Bubble M-type main-sequence stars Planetary systems with three confirmed planets J02530084+1652532 Astronomical objects discovered in 2003 Stars with proper names