Lalande 21185 (also known as BD+36 2147, Gliese 411, and HD 95735
) is a star in the south of
Ursa Major
Ursa Major (; also known as the Great Bear) is a constellation in the northern sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater (or larger) bear," referring to and contrasting it with nearby Ursa ...
. It is the
apparent brightest
red dwarf
''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...
in the northern hemisphere.
[Only ]AX Microscopii
Lacaille 8760 (AX Microscopii) is a red dwarf star in the constellation Microscopium. It is one of the nearest stars to the Sun at about 12.9 light-years' distance, and the brightest M dwarf star in Earth's night sky, although it is ...
and Lacaille 9352
Lacaille 9352 (Lac 9352) is a red dwarf star in the southern constellation of Piscis Austrinus. With an apparent visual magnitude of 7.34, this star is too faint to be viewed with the naked eye except possibly under excellent seeing co ...
, in the southern hemisphere, are brighter Despite this, and being relatively close by, it is (as are all red dwarfs) very dim, being only
magnitude 7.5 in
visible light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
and thus too faint to be seen with the unaided eye. The
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
is visible through a small telescope or binoculars.
[
At approximately ][ away it is one of the stars nearest to the Solar System; only the ]Alpha Centauri
Alpha Centauri ( Latinized from α Centauri and often abbreviated Alpha Cen or α Cen) is a triple star system in the constellation of Centaurus. It consists of 3 stars: Alpha Centauri A (officially Rigil Kentaurus), Alpha Centaur ...
system, Barnard's Star
Barnard's Star is a red dwarf about six light-years from Earth in the constellation of Ophiuchus. It is the fourth-nearest-known individual star to the Sun after the three components of the Alpha Centauri system, and the closest star in the ...
, and Wolf 359
Wolf 359 is a red dwarf star located in the constellation Leo, near the ecliptic. At a distance of approximately 7.9 light years from Earth, it has an apparent magnitude of 13.54 and can only be seen with a large telescope. Wolf 359 i ...
and the 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 ...
s Luhman 16
Luhman 16 (WISE 1049−5319, WISE J104915.57−531906.1) is a binary brown-dwarf system in the southern constellation Vela at a distance of approximately from the Sun. These are the closest-known brown dwarfs and the closest syst ...
and WISE 0855−0714
WISE 0855−0714 (full designation WISE J085510.83−071442.5, or W0855 for short) is a sub-brown dwarf () from Earth, therefore the fourth- closest star or (sub-) brown dwarf system to the Sun, the discovery of which was announced i ...
are known to be closer. Because of its proximity it is a frequent subject for astronomical surveys and other research and thus is known by numerous other designations, most commonly Gliese 411 and HD 95735. In approximately 19,900 years it will be at its closest, about 4.65 ly (1.43 pc) from the Sun, just over half its present distance.
History
The celestial coordinates
Astronomical coordinate systems are organized arrangements for specifying positions of satellites, planets, stars, galaxies, and other celestial objects relative to physical reference points available to a situated observer (e.g. the true hor ...
of Lalande 21185 were first published in 1801 by French astronomer Jérôme Lalande of the Paris Observatory
The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its histor ...
in the star catalog ''Histoire céleste française
''Histoire céleste française'' (''French Celestial History'') is an astrometric star catalogue published in 1801 by the French astronomer Jérôme Lalande and his staff at the Paris Observatory. This star catalog consists of the locations and ...
''. The catalog sequence numbers for majority of the observed stars, including this one, were introduced in its 1847 edition by Francis Baily
Francis Baily (28 April 177430 August 1844) was an English astronomer. He is most famous for his observations of "Baily's beads" during a total eclipse of the Sun. Baily was also a major figure in the early history of the Royal Astronomical S ...
. Today this star is one of just a few that are still commonly referred to by their Lalande catalog number.
In May 1857, Friedrich Wilhelm Argelander discovered the high proper motion
Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...
of the star. It was sometimes called "Argelander's second star". (The "first Argelander's star" is Groombridge 1830
Groombridge 1830 (also known as 1830 Groombridge or Argelander's Star)Peters, C. A. F.; "On the Parallax of Argelander's Star", Monthly Notices of the Royal Astronomical Society, December 1853, v.50, p.302, is a star in the constellatio ...
, whose high proper motion was discovered by Argelander earlier—in 1842).
Friedrich August Theodor Winnecke is reported to have made the first measurement of the star's parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...
of 0.511 arc seconds
A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of Angular unit, angular measurement equal to of one Degree (angle), degree. Since one degree is of a turn (geometry), turn (or complete rotat ...
in 1857–58 and thus first identifying Lalande 21185 as the second-closest-known star to the Sun, after the Alpha Centauri
Alpha Centauri ( Latinized from α Centauri and often abbreviated Alpha Cen or α Cen) is a triple star system in the constellation of Centaurus. It consists of 3 stars: Alpha Centauri A (officially Rigil Kentaurus), Alpha Centaur ...
system. Since that time better measurements have placed the star farther away, but it remained the second-closest-known star system until the astrophotographic discovery of two dim red dwarfs, Wolf 359 and Barnard's Star, in the early 20th century.
Properties
Lalande 21185 is a typical type-M main-sequence
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hert ...
star (red dwarf
''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...
) with about 39% of the mass of the Sun[ and is much cooler than the Sun at 3,550 K. It is intrinsically dim with an ]absolute magnitude
Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...
of 10.48, emitting most of its energy in the infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
.[ The proportion of elements other than hydrogen and helium is estimated based on the ratio of iron to hydrogen in the star when compared to the Sun. The logarithm of this ratio is −0.20, indicating that the proportion of iron is about 10−0.20, or 63% of the Sun. The surface gravity of this relatively compact star is approximately 65 times greater than the gravity at Earth's surface (log g = 4.8 cgs),][ which is more than twice the surface gravity of our Sun.
]
Lalande 21185 is listed as a BY Draconis
BY Draconis is a multiple star system in the constellation Draco, consisting of at least three components. Components A and B are main sequence stars, and form a close binary star system with a short orbital period of only 5.98 days. ...
type variable star in the General Catalogue of Variable Stars. It is identified by the variable star designation NSV 18593. Several star catalogs, including SIMBAD
SIMBAD (the Set of Identifications, Measurements and Bibliography for Astronomical Data) is an astronomical database of objects beyond the Solar System. It is maintained by the Centre de données astronomiques de Strasbourg (CDS), France.
SIMBA ...
, also classify it as a flare star. This conclusion is not supported by the primary reference these catalogs all use. The observations made in this reference show that it is rather quiet in comparison to other stars of its variable type.
Lalande 21185 emits X-rays, and X-ray flares have been observed.
It is the brightest star between variable CO Ursae Maj and the comparably bright star HD 95129 to its west ( specifically by south) and is a little closer to the latter.
Planetary system
Data published in 2017 from the HIRES system at the Keck Observatory
The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when comp ...
on Mauna Kea
Mauna Kea ( or ; ; abbreviation for ''Mauna a Wākea''); is a dormant volcano on the island of Hawaii. Its peak is above sea level, making it the highest point in the state of Hawaii and second-highest peak of an island on Earth. The peak is ...
supported the existence of a close-in planet with an orbital period of just 9.8693±0.0016 days, being at least .
Further radial velocity research with the SOPHIE échelle spectrograph The SOPHIE (Spectrographe pour l’Observation des Phénomènes des Intérieurs stellaires et des Exoplanètes, literally meaning "spectrograph for the observation of the phenomena of the stellar interiors and of the exoplanets") ''échelle spectrog ...
and review of the original signal found that the 9.9 day period was undetectable, and instead proposed, using both datasets, an exoplanet orbiting the star with a period of either 12.95 or 1.08 days, much more likely 12.95, insofar as 1-day-period exoplanets seem to be rare in systems. This would give the planet a minimum mass of 2.99 Earth masses. It is too close to the star, and so therefore too hot, to be in the habitable zone, at all points within its eccentric orbit. The proposed planet on 12-day orbit was confirmed by (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs) project in 2020.
A second planet with a more distant orbit was initially noticed by SOPHIE, but the baseline was not long enough to confirm the several-year-long signal. The signal was confirmed in 2021 to be a planet with mass at least , a lower-bound estimate later revised to .[
A third planet, Gliese 411 d, is suspected to orbit between Gliese 411 b and Gliese 411 c with a period of 215 days.][
The habitable zone for this star, defined as the locations where liquid water could be present on an Earth-like planet, is at a radius of 0.11–0.24 AU, where 1 AU is the average distance from the Earth to the Sun.] The planet b has an equilibrium temperature of 370.1 K. Other known planets are outside HZ boundaries too, but undetected low-mass ones may be orbiting in this region of this system as well.[
]
Past claims of planets
Dutch astronomer Peter van de Kamp
Piet van de Kamp (December 26, 1901 in Kampen (Overijssel), KampenLaurence W. Fredrick, Peter van de Kamp (1901–1995)', Publications of the Astronomical Socitiey of the Pacific 108:556–559, July 1996 – May 18, 1995 in Amsterdam), known a ...
wrote in 1945 that Lalande 21185 possessed an "unseen companion" of (about ). In 1951 van de Kamp
A van is a type of road vehicle used for transporting goods or people. Depending on the type of van, it can be bigger or smaller than a pickup truck and SUV, and bigger than a common car. There is some varying in the scope of the word across th ...
and his student Sarah Lippincott
Sarah Lee Lippincott (October 26, 1920 – February 28, 2019), also known as Sarah Lee Lippincott Zimmerman, was an American astronomer. She was professor emerita of astronomy at Swarthmore College and director emerita of the college's Sproul Ob ...
claimed the astrometric detection of a planetary system using photographic plates taken with the refractor telescope at Swarthmore College
Swarthmore College ( , ) is a Private college, private Liberal arts colleges in the United States, liberal arts college in Swarthmore, Pennsylvania. Founded in 1864, with its first classes held in 1869, Swarthmore is one of the earliest coeduca ...
's Sproul Observatory
Sproul Observatory was an astronomical observatory owned and operated by Swarthmore College. It was located in Swarthmore, Pennsylvania, United States, and named after William Cameron Sproul, the 27th Governor of Pennsylvania, who graduated ...
. In the summer of 1960, Sarah Lippincott altered the 1951 claim, to a planet of (that is, ), an 8-year orbital period, eccentricity of 0.3, a semi-major axis[which would be orbital radius if e was 0, that is, a circular orbit] of . She used the original photographic plates and new plates taken with the same telescope. Photographic plates from this observatory, taken at the same time, were used by Van de Kamp for his erroneous claim of a planetary system for Barnard's Star
Barnard's Star is a red dwarf about six light-years from Earth in the constellation of Ophiuchus. It is the fourth-nearest-known individual star to the Sun after the three components of the Alpha Centauri system, and the closest star in the ...
. The plates made with the Sproul 24-inch refractor and used for these and other studies were in 1973 shown to be flawed; as they were the next year with astrometric measurements made by George Gatewood
George David Gatewood (born 1940) also known as ''George G. Gatewood'', is an American astronomer and presently is professor emeritus at the University of Pittsburgh and at the Allegheny Observatory. He specializes in astronomy, astronomical instru ...
of the Allegheny Observatory.
In 1996 the same Gatewood prominently announced at an AAS meeting and to the popular press the discovery of multiple planets in this system, detected by astrometry. The initial report was based on a very delicate analysis of the star's position over the years, which suggested reflex orbital motion due to one or more companions. Gatewood claimed that such companions would usually appear more than 0.8 arcseconds from the red dwarf itself. Though, a paper by Gatewood published only a few years earlier and later searches by others, using coronagraphs and multifilter techniques to reduce the scattered-light problems from the star, did not positively identify any such companions, and so his claim remains unconfirmed and is now in doubt.
Before the 1980s, finding the radial velocity of red dwarf
''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...
s was neither very accurate nor consistent, and so due to its apparent brightness and because it does not have a companion, this star, along with eleven other similar red dwarf stars, were chosen to have their radial velocity
The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...
measured, to unprecedented high accuracy, by planet hunter Geoff Marcy. No companion was detected around this star in this nor other contemporary surveys, and such early equipment would have picked up any planet exceeding in an extremely close orbit of 5 days or less; or exceeding at about Jupiter's orbital distance.
See also
* 70 Ophiuchi
70 Ophiuchi is a binary star system located 16.6 light years away from the Earth. It is in the constellation Ophiuchus. At magnitude 4 it appears as a dim star visible to the unaided eye away from city lights.
History
In the Ptolemy's ...
* Barnard's Star
Barnard's Star is a red dwarf about six light-years from Earth in the constellation of Ophiuchus. It is the fourth-nearest-known individual star to the Sun after the three components of the Alpha Centauri system, and the closest star in the ...
* List of nearest stars
* Wolf 359
Wolf 359 is a red dwarf star located in the constellation Leo, near the ecliptic. At a distance of approximately 7.9 light years from Earth, it has an apparent magnitude of 13.54 and can only be seen with a large telescope. Wolf 359 i ...
References
Notes
External links
*
*
''Extrasolar Planets Encyclopaedia'': Confirmed
planet candidate
super-Earth planet Lalande 21185 b. Retrieved 2017-02-15
{{2021 in space
095735
High-proper-motion stars
054035
0411
BD+36 2147
Local Bubble
M-type main-sequence stars
Ursa Major (constellation)
Planetary systems with two confirmed planets
BY Draconis variables
J11032023+3558117