Luyten's Star

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NASA -- larger image

Luyten's is a dim red dwarf star, like Gliese
623 A (M2.5V) and B (M5.8Ve) at lower right.
(See a Digitized Sky Survey field image around
Luyten's at the Nearby Stars Database.)

System Summary

Luyten's Star is located about 12.4 light-years (ly) from our Sun, Sol. It lies in the northern part (07:27:24.50+05:13:32.83, ICRS 2000.0) of Constellation Monoceros, the Unicorn, near Constellation Canis Minor (the Smaller Dog), -- 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). 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 images of Luyten's Star are available from the SIM Teams). Astronomers are also hoping to use the ESA's Darwin group of infrared interferometers to analyze the atmospheres of any rocky planet found in the "habitable zone" (HZ) around Luyten's Star for evidence of Earth-type life (Lisa Kaltenegger, 2005).

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.

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 percent of its diameter, and 4/10,000th of its luminosity. 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.

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

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. 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.

Closest Neighbors

The following star systems are located within 10 light-years of Luyten's Star.

Star System	Spectra & Luminosity	Distance (light-years)
Procyon AB	F5 V-IV DA-F/VII	1.2
Ross 614 AB	M4.5 Ve ?	3.9
DX Cancri	M6.5 Ve	5.5
LTT 12352	M3.5 V	5.6
Sirius 2	A0-1 Vm DA2.5/VII	5.8
Ross 882 AB	M4 Ve M5 Ve	7.1
LTT 17897	M4 V	7.7
LTT 17993	M4.5 V	7.7
GJ 1116 AB	M5.5 V M5.5 V	8.0
Wolf 294	M3 V	9.4
Ross 47	M4 V	9.6
Wolf 359	M5.8 Ve	9.8

Other Information

Up-to-date technical summaries on these stars can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARICNS, the Nearby Stars Database and the Research Consortium on Nearby Stars (RECONS) list of the 100 Nearest Star Systems. Additional information may be available at Roger Wilcox's Internet Stellar Database.

Although this constellation 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.