Luyten 675-81 / Gliese 317

NASA -- larger image

Gliese 317 is a dim red dwarf star, like Gliese 623 A (M2.5V)
and B (M5.8Ve) at lower right. (An image of Gliese 433 may
become available from the 2MASS Survey at the NASA Star
and Exoplanet Database.)

System Summary

Also known as Luyten (L) 575-81, this dim star may lie 29.9 +/- 5.5 light-years from Sol (Johnson et al, 2007, based on an adopted average of two parallaxes). It is located in the north central part (8:40:59.2-23:27:23.3, ICRS 2000.0) of Constellation Pyxis, the Compass -- northeast of Gamma Pyxidis and Alpha (Alpha Pyx) and Beta Pyxidis, east of Tureis (Rho Puppis), and southwest of Alphard (Alpha Hydrae). Like other red dwarf stars, however, it is not visible to the naked eye. On July 16, 2007, a team of astronomers submitted a pre-print announcing the discovery of possibly as many as two Jupiter-class planets around Gliese 317 (press release and Johnson et al, 2007 -- details below). (See an animation of the planetary and potentially habitable zone orbits of this system, with a table of basic orbital and physical characteristics.)

Its high proper motion was probably discovered photographically, and it was designated as L 675-81 by Willem Jacob Luyten (1899-1994), who found the proper motions of over 520,000 stars despite the loss of sight in one eye since 1925 by building an automated photographic plate scanner and measuring machine. Today, many astronomers refer to this star by its earliest designation as Gl 317 in the first Gliese Catalogue of Nearby Stars (CNS, now ARICNS database) of Wilhelm Gliese (1915-93), who was a longtime astronomer at the Astronomiches Rechen-Institut at Heidelberg (even when it was at Berlin).

The Star

Gliese 317 is a cool and dim, main sequence red dwarf of spectral and luminosity type M3.5 V, but once classed as orange as M0 (NASA Star and Exoplanet Database). The star has 24 +/- 4 percent) of Sol's mass (Johnson et al, 2007), possibly less than 40 percent of its diameter, and slightly less than 0.13 percent of its visual luminosity. The star appears to be around 59 percent as enriched as Sol in elements heavier than hydrogen Johnson et al, 2007). Some other useful star catalogue designations include: Gl 317, LHS 2037, LTT 3215, LP 844-8, LPM 296, LFT 598, L 675-81, and 2MASS J08405923-2327232.

Planetary System?

On July 16, 2007, a team of astronomers submitted a pre-print announcing the discovery of possibly as many as two Jupiter-class planets around Gliese 317 (press release and Johnson et al, 2007). Planet "b" appears to have at least 1.2 Jupiter-masses. With a semi-major axis of 0.95 AU, it has an eccentric orbit (e~ 0.193) around Gliese 317 which takes 692.9 days or 1.9 years to complete. There may be another planet "c" with 83 percent of a Jupiter-mass and a roughly 2,700-day (7.4-year) orbit, which will take more years of observations to verify. Based on its bolometric luminosity, a planet may be able to hold water on its surface somewhere roughly between 0.1 and 0.2 AUs of Gliese 317. (See an animation of the planetary and potentially habitable zone orbits of this system, with a table of basic orbital and physical characteristics.)

NASA, Cassini-Huygens Mission
to Saturn and Titan

Larger image.

Gliese 317 may have as many
as two planets massive enough
to be a gas giant like Jupiter
(shown here with Europa).

Closest Neighbors

The following star systems are located within 10 ly of Gliese 317.

Star System Spectra &
Luminosity Distance
(light-years)
CD-32 5613 DA6 /VII 4.1
L 678-39 K-M3 V 6.6
L 745-46 AB DZQ6 /VII
M6 V 8.3
GJ 1129 M V 9.5
BD-12 2918 AB M2-3 V
? 9.8
L 672-19 M V 9.9

Other Information

Star System	Spectra & Luminosity	Distance (light-years)
CD-32 5613	DA6 /VII	4.1
L 678-39	K-M3 V	6.6
L 745-46 AB	DZQ6 /VII M6 V	8.3
GJ 1129	M V	9.5
BD-12 2918 AB	M2-3 V ?	9.8
L 672-19	M V	9.9