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Luyten's Star is located about 12.4 light-years (ly) from our Sun, Sol. It lies in the south western corner (07:27:24.50+05:13:32.83, ICRS 2000.0) of Constellation Canis Minor (the Smaller Dog), at the border with Constellation Monoceros, the Unicorn -- east of the Rosette Nebula (NGC 2237, 2238, 2239, and 2246) and southwest of Gomeisa (Beta Canis Minoris) and west of Procyon (Alpha Canis Minoris), which is its closest known stellar neighbor at only around 1.1 light-years away. The high proper motion of this dim star was probably discovered 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.
Due to Luyten's Star's proximity to Sol, the star has been an object of high interest among astronomers. It has been selected as a "Tier 1" target star for NASA's optical Space Interferometry Mission (SIM) to detect a planet as small as three Earth-masses within two AUs of its host star (and so some summary system information and may still be available from the SIM Teams). The SIM project manager announced on November 8, 2010, however, that the mission was indefinitely postponed due to withdrawal of NASA funding.
Medialab, ę ESA
Larger illustration of
the Darwin Mission.
Astronomers have identified
Luyten's Star as a prime target
for NASA's optical SIM and the
ESA's infrared Darwin missions,
now both indefinitely postponed.
Luyten's Star is is a main sequence red dwarf star of spectral and luminosity type M3.5 Vn. The star has about 25.7 percent of Sol's mass (RECONS), about 11 to 33 percent of its diameter (NASA Star and Exoplanet Database, derived from the power law formula of Kenneth R. Lang, 1980), and 4/10,000th of its visual luminosity and around one percent of its bolometric luminosity (NASA Star and Exoplanet Database, derived from the exponential formula of Kenneth R. Lang, 1980). Within a large error margin (Fe/H= -0.16 +/- 0.20), the star may have around 69 percent of Sol's abundance of iron relative to hydrogen (a sub-Solar metallicity (Bonfils et al, 2005; as cited in Shkolnik et al, 2009, Table 3 for GJ 273). Some useful names and catalogue numbers for this star include: Gl 273, Hip 36208, BD+05 1668, G 89-19, G 112-17, LHS 33, LTT 12021, LFT 527, L 5-1668, and V 17.
Accounting for infrared heating, the distance from the star where an Earth-type planet would be "comfortable" with liquid water is centered around 0.15 AUs, where its orbital period would be competed in less than 42 days (SIM summary data). In that distance range from the star, such a planet would have an orbital period shorter an Earth year. According to alternative calculations performed for the NASA Star and Exoplanet Database, their estimate of the HZ is similarly centered around 0.150 AU, with inner edge of Luyten's Star's habitable zone at around 0.102 AU from the star, while the outer edge lies farther out at around 0.198 AU. At such a close in orbit, however, the rotation of the planet may become tidally locked with the star so that one side would have eternal daylight and the other would be in darkness.
Luyten's Star b?
Astrometic analysis of photographic plates and measures taken from 1937 to 1980 suggested Luyten's Star may have a substellar companion. Assuming an upper limit for mass of Luyten's Star at two tenths of a Solar mass and the semi-major axis of orbit around the star, three upper limit possibilities were derived: 1.1 Jupiter-mass with an orbital period of 10 years; 0.7 Jupiter-mass with a 20-year period; or a 0.4 Jupiter-mass with a 40-year period orbit. (Hersey and Lippincott, 1982). Subsequent, radial velocity searches for such an object were negative (Marcy and Benitz, 1989; and Young et al, 1987). More recently, infrared speckle interferometric searches for companions with a mass between 50 an 80 Jupiter-masses at 1-10 AUs and 100-1,000 AUs of Luyten's Star also have not been able to confirm the existence of such an object (Simons et al, 1996; and Henry and McCarthy, 1990).
Hunt for Substellar Companions
None detected and announced to the general public as of 2011.
The following star systems are located within 10 light-years of Luyten's Star.
|Star System||Spectra &|
|Procyon AB||F5 V-IV |
|Ross 614 AB||M4.5 Ve |
|DX Cancri||M6.5 Ve||5.5|
|LTT 12352||M3.5 V||5.6|
|Sirius 2||A0-1 Vm |
|Ross 882 AB||M4 Ve |
|LTT 17897||M4 V||7.7|
|LTT 17993||M4.5 V||7.7|
|GJ 1116 AB||M5.5 V |
|Wolf 294||M3 V||9.4|
|Ross 47||M4 V||9.6|
|Wolf 359||M5.8 Ve||9.8|
Up-to-date technical summaries on these stars can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARICNS, the NASA Star and Exoplanet Database, the Research Consortium on Nearby Stars (RECONS) list of the 100 Nearest Star Systems, and the SIMBAD Astronomical Database. Additional information may be available at Roger Wilcox's Internet Stellar Database.
Constellation Canis Minor (the Lesser Dogs) and Canis Major (the Greater Dogs) follow legendary Orion (the Hunter). Canis Minor appears to have been thought of as a well-trained house or watch dog, who also accompanied Orion on his hunting trips. For more information about the stars and objects in this constellation, go to Christine Kronberg's Canis Minor. For an illustration, see David Haworth's Canis Minor.
Although Constellation Monoceros may have been named for the Unicorn prior to the 17th century, its first known historical reference is in Jakob Bartsch's star chart of 1624 as "Unicornu." Bartsch, the son-in-law of Johannes Kepler, is believed to have relied on earlier works that have never been identified. For more information about the stars and objects in this constellation, go to Christine Kronberg's Monoceros. For an illustration, see David Haworth's Monoceros.
For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.
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