Alpha Mensae

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NASA

Alpha Mensae is a yellow-orange star
like our Sun, Sol. (See a Digitized
Sky Survey image of Alpha Mensae
from the Nearby Stars Database.)

System Summary

Alpha Mensae is located about 33.1 light-years from Sol. It lies in the northeastern part (06:10:14.47-74:45:10.96, ICRS 2000.0) of Constellation Mensa, the Table Mountain -- west of Zeta Volantis, southwest of Gamma2 Volantis, and south of the Large Magellanic Cloud. As Alpha Mensae has become one of the top 100 target stars for NASA's planned Terrestrial Planet Finder (TPF), images of this star and its position relative to the Milky Way in Earth's night sky are now available from the TPF-C team.

JPL, CalTech, NASA

Larger illustration

Astronomers have identified Alpha
Mensae as a prime target for the
Terrestrial Planet Finder (TPF),
now planned for launch between
2014 and 2020.

The Star

Alpha Mensae is a yellow-orange main sequence dwarf star of spectral and luminosity type G5-6 V, with about 87 percent of Sol's mass, 84 to 91 percent of its diameter (Perrin and Karoji, 1987, page 236; and Johnson and Wright, 1983, page 659), and around 80 percent of its luminosity. The star may be as as enriched (102 percent) as Sol with elements heavier than hydrogen ("metallicity"), based on its abundance of iron (Cayrel de Strobel et al, 1991, page 285). Useful star catalogue numbers for the star include: Alp Men, Alf Men, HR 2261, Gl 231, Hip 29271, HD 43834, CP(D)-74 374, SAO 256274, FK5 239, and LTT 2490.

Hunt for Substellar Companions

The orbit of an Earth-like planet (with liquid water) around this star would be centered around 0.91 AU -- between the orbital distances of Venus and Earth in the Solar System -- with an orbital period of nearly 342 days, close to an Earth year. Astronomers are hoping to use NASA's Terrestrial Planet Finder (TPF) and the ESA's Darwin planned groups of observatories to search for a rocky inner planet in the so-called "habitable zone" (HZ) around Alpha Mensae. As currently planned, the TPF will include two complementary observatory groups: a visible-light coronagraph to launch around 2014; and a "formation-flying" infrared interferometer to launch before 2020, while Darwin will launch a flotilla of three mid-infrared telescopes and a fourth communications hub beginning in 2015.

Closest Neighbors

The following star systems are located within 10 light-years of Alpha Mensae.

Star System	Spectra & Luminosity	Distance (light-years)
Hip 31293	?	4.6
Hip 31292	?	5.9
CP(D)-69 177	DA /VII	8.6
LHS 263 / GJ 1123	M V	8.8
LHS 205 / GJ 1077	M 1.5 V	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). Additional information may be available at Roger Wilcox's Internet Stellar Database.

Located in a South Polar region of the sky that lacks bright stars above 5th magnitude and other interesting objects, Constellation Mensa was named by the Abbé [Abbot] Nicholas Louis de La Caille (1713-1762). The original name, Mons Mensa, after the table mountain near de Lacaille's observatory in Cape Town, South Africa, was shortened when the International Astronomical Union (IAU) defined the 88 constellations that exist today. For more information about the stars and objects in this constellation, go to Christine Kronberg's Mensa. For another illustration, see David Haworth's Mensa.

For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.