Luyten's Star

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, © ESA 2002



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.

The Star

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.

Habitable Zone

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.

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