Lalande 21185

Starbox begin
name = Lalande 21185Starbox observe
epoch = J2000.0
constell = Ursa Major
ra = RA|11|03|20.2
dec = RA|+35|58|11
appmag_v = 7.47Starbox character
class = M2V
r-i =
v-r =
b-v = 1.51
u-b = 1.13
variable = Flare starStarbox astrometry
radial_v = -84.8
prop_mo_ra = -580.20
prop_mo_dec = -4767.09
parallax = 393.42
p_error = 0.70
parallax_footnote =
dist_ly =
dist_pc =
space_v_u =
space_v_v =
space_v_w =
absmag_v = 10.46Starbox detail
source =
mass = 0.46
radius = 0.46
gravity =
luminosity = 0.0016
temperature = 3,400
metal = 63% Sun
rotation =
age = 5-10 × 10⁹Starbox catalog
names = BD+36 2147, G 119-052, Gliese 411, HD 95735, HIP 54035, LFT 756, LHS 37, LTT 12960, MCC 594, PLX 2576, SAO 62377Starbox reference
Simbad = HD+95735
ARICNS =

Lalande 21185, often abbreviated as LAL 21185, is a red dwarf star approximately 8 light-years away in the constellation of Ursa Major (the Great Bear). The star is currently the fourth closest star to the Solar system moving at a relatively high velocity in an orbit perpendicular to the plane of the galaxy. The star is also a variable flare star that sometimes increases in brightness. Based on an analysis of astrometric perturbations, Lalande 21185 is thought to possess at least two Jupiter-sized extrasolar planets. This earliest recording of the star was by French astronomer Joseph-Jérôme Lefrançais de Lalande at the Paris Observatory some time before 1801 (this is also where the star gets its name).

Stellar components

Lalande 21185 is a cool and dim red dwarf star of the spectral type of M2.1Vne. The star is thought to have only 46 percent of the Sun's mass, 46 percent of the radius, and less than 1,000th of the luminosity. The star is less enriched in elements heavier than hydrogen compared to the Sun, with around 63 percent iron.

The star moves in a perpendicular orbit around the galactic plane (at a fast velocity of 47 km/sec). Lalande 21185 is thought to belong to a "thick disk" of the Milky Way, a cluster of old stars that move rapidly within 5,000 light-years of the galactic plane in considerably eccentric orbits. Because Lalande is a flare star, the star is assumed to be much older than the Sun, making Lalande 21185 approximately 10 billion years old.

Possible planetary system

The first signs of Lalande 21185 having extrasolar planets came in 1996 when a team of astronomers reported the detection of possible planetary companions. The planetary system was detected from astrometric perturbation analysis of photographic plate data collected from 1930 to 1984, and from tracking the star's motion from 1988 to the present using a Multichannel Astrometric Photometer. A second planet may lie about 11 astronomical units away in the first planet's orbital plane. If the second planet's mass has not been significantly underestimated, then there may be a third planet lying beyond 11 astronomical units with around one Jupiter mass and a longer orbital period.

In September of 2002, a team of astronomers announced that they had detected water "maser" emissions from three of 17 star systems suspected of hosting planets (including Lalande 21185). These microwave emissions could be generated from water molecules in a possible planet's atmosphere when they are excited by the infrared light of its host star. In an interview with Astronomer Hugh Jones, he stated that the signals could have come from the parent star and not planets, but that additional telescopic observation should be able to pinpoint the exact source of the signal. Astronomer Geoff Marcy would later add that water maser emissions from the planets would not be strong enough to be detected from the Earth.

PlanetboxOrbit hypothetical
exoplanet = b
mass = 0.9
semimajor = 2.0
period = 2118.508
eccentricity = 0PlanetboxOrbit hypothetical
exoplanet = c
mass = 1.6
semimajor = 10.0
period = 10957.8
eccentricity = 0PlanetboxOrbit hypothetical
exoplanet = d
mass = <1
semimajor = <11
period = <30
eccentricity = 0

See also

* HD 189733 b
* Lalande 21185 in fiction
* List of nearest stars

External links

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