Gliese 570 ABCD

Star type
g A: K4 V - K5
g B: M1 V
g C: M3 V
g D: T8 (brown dwarf)

Distance from Earth
g 19.2-19.26 ly

Star Service No.
g NA

Age
g A: NA
g B: NA
g C: NA
g D: 2-5 by

Diameter/Mass/Temp (xSol)
g A: 77%; 76%; NA
g B: 66%; 55%; NA
g C: NA; 35%; NA
g D: NA; 50 +/- 20 Jupiters; 900° F (coolest brown dwarf known)

Brightness (xSol)
g A: 15.6%; the star brightens and dims by about 50 percent over a a period of 10 days due to large star spots
g B: 1.9%
g C: 0.3%
g D: NA

Metallicity
g A: 102%
g B: 102% (?)
g C: 102% (?)
g D: NA

Comparison to Sol
g A: See chart (smaller than Alpha Centauri B but larger than GJ 205)
g B: See chart (similar to Proxima)
g C: See chart (similar to Proxima)
g D: See chart (similar to Gliese 229B)

Picture of star
g A: See picture (star is above a pair)
g B: See picture (star is one of pair below single star)
g C: See picture (star is one of pair below single star)
g D: See picture
g D: Artist’s interpretation of brown dwarf orbiting Stars A, B and C

Star system features
g Star A and the close binary pair BC have a wide average separation of about 190 AUs, moving in an eccentric orbit (e= 0.20) that lasts some 2,130 years; B and C pair of stars have an average separation around 0.79 AUs in a highly eccentric orbit (e= 0.765) lasting about 309 days; brown dwarf is separated from this trinary by more than 1,500 AUs
g Article about star system: "Astronomers Unveil Hot Photo of Cool Star"

Known planets
g A: None found
g B: None found
g C: None found
g D: None found

Habitable zone
g A: Star A's late spectral type and dim luminosity puts it possibly close to the lower limit of habitability for (multicellular) Earth-type plant and animal life, given the redness of its light and the increased risk of tidal locking from the closeness of the orbit necessary for liquid water on a planetary surface. The distance from Star A where an Earth-type planet would be "comfortable" with liquid water is centered around 0.40 AU -- within the orbital distance of Mercury in the Solar System. At that distance from the star, such a planet would have an orbital period of 104 days.
g B: Water zone orbit lies near 0.14 AU. Assuming that Star C does not perturb its orbital stability, a planet in Star B's water zone would have a period of about 25 days. However, tidal locking of such a closely orbiting planet would resulting in perpetual day on one side and perpetual night on the other.
g C: Water zone orbit lies near 0.056 AU. Assuming that Star B does not perturb its orbital stability, a planet in Star C's water zone would have a period of about 8.2 days. However, tidal locking of such a closely orbiting planet would resulting in perpetual day on one side and perpetual night on the other.
g D: Could possibly support life on a mall moon with a thick atmosphere; the star would glow dull red, like the embers of a dying fire, in the sky

Orbital map
g See map

View from star
g A: See sky map
g B: See sky map
g C: See sky map
g D: See sky map (virtually identical to Stars A, B and C)

Nearby stars
(Star systems with 10 light years)
g LP 914-54: 1.9 ly
g BD-11 3759: 3.6 ly
g Hip 72509: 4.8 ly
g Gl 581/HO Librae: 5.2 ly
g CD-25 10553 AB: 5.5 ly
g GJ 588: 7.1 ly
g L 768-119: 8.6 ly

Map locating star system
g See stellar map (Listed as “Lalande 27173”)

Location in Earth sky
g In the southwestern part of Constellation Libra, the Scales, southwest of Zebenelgenubi (Alpha2 Librae) and northwest of Sigma Libra; Star A is a relatively bright star in Earth's night sky

Other names
g HR 5568 ABCD, Lalande 27173 ABCD
g A: Hip 73184, LHS 387, HD 131977, BD-20 4125, SAO 183040, FK5 1391, LTT 5949, LFT 1161, LPM 551, Vys or McC 726 A, ADS 9446 A
g B: HD 131976, Hip 73182, BD-20 4123, SAO 183039, Vys or McC 726 B, LTT 5948, LFT 1160, LPM 550, ADS 9446 B, LHS 386
g C: ADS 9446 C, BD-20 4123 B, SAO 183039 B, Vys or McC 726 C, LHS 386 B

Sci-fi mentions
g NA

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