37 Geminorum

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NASA

37 Geminorum is a yellow-orange star
like our Sun, Sol. (See a Digitized
Sky Survey image of 37 Geminorum
from the Nearby Stars Database.)

System Summary

37 Geminorum is located about 56.3 light-years (ly) from Sol. It lies in the northwest part of (6:55:18.7+25:22:32.5, ICRS 2000.0) of Constellation Gemini, the Twins -- west of Mebsuta (Epsilon Geminorum), northeast of Mu (Teja) and Eta (Propus) Geminorum, northwest of Zeta (Mekbuta) and Delta (Wasat) Geminorum, and east of open cluster M35. In late September 2003, astrobiologist Maggie Turnbull from the University of Arizona in Tucson identified 37 Geminorum as one of the best candidates for hosting Earth-type life from a shortlist of 30 stars (screened from the 5,000 or so stars that are estimated to be located within 100 ly of Earth) that were presented to a group of scientists from NASA's space-telescope project, the Terrestrial Planet Finder (TPF), which will search for habitable planets by using visible light with the "signature" of water and/or oxygen from an Earth-type planet after its scheduled launch around 2013, and the ESA's Darwin project involving six space telescopes (Astrobiology Magazine). The stars examined were selected from a larger list of 17,129 (of which 75 percent are located within around 450 ly, or 140 parsecs, of Sol) that were assembled into a Catalog of Nearby Habitable Stellar Systems (HabCat) by Turnbull and Jill Tarter of the SETI Institute (see: Margaret C. Turnbull, 2002, in pdf). Selection criteria for the 30-star shortlist included: X-ray luminosity, rotation, spectral types or color, kinematics, metallicity, and Strömgren photometry.

Medialab, NASA
© ESA 2001

Larger image.

To find life around nearby stars,
the ESA's Darwin mission will look
for traces of water, oxygen, and
carbon dioxide in the atmospheres
of Earth-type planets found in
stellar habitable zones (more).

The Star

37 Geminorum (Gem) is a yellow-orange main sequence dwarf star of spectral and luminosity type G0 V. A little bigger and brighter than Sol, the star may have 1.1 times Sol's mass, 1.03 times its diameter (Johnson and Wright, 1983, page 661), and 1.25 times its luminosity. Similarly middle-aged, however, 37 Gem appears to be around 5.5 billion years old -- somewhat older than Sol's 4.6 billion years -- and so may be old enought to have developed oxygen-generating life as happened on Earth after two billion years. Useful catalogue numbers and designations for the star include: 37 Gem, HR 2569, Gl 252, HIP 33277, HD 50692, BD+25 1496, and SAO 78866.

Hunt for Planetary Objects

Past radial velocity analysis suggests that giant planets of one tenth to 10 times the mass of Jupiter do not exist within 0.1 to four AUs of 37 Gem (Cummings et al, 1999). If so, then conditions would be more favorable for the existence of stable orbit for an Earth-like planet (with liquid water) centered around 1.12 AU from around 37 Gem -- between the orbital distances of Earth and Mars in the Solar System. Such a planet would have an orbital period of around 1.3 years. Astronomers would find it very difficult to detect an Earth-sized planet around this star using present methods.

Closest Neighbors

The following table includes all star systems known to be located within 10 light-years (ly), plus more bright stars within 10 to 20 ly, of 37 Gem.

Star System	Spectra & Luminosity	Distance (light-years)
LP 308-10	DC9 /VII	1.4
BD+30 1367a	K7-M0 V	2.6
BD+24 1357	K2-6 V	3.6
Wasat AabB	F0-2 V-IV ? K3-6 V	7.1
BD+29 1441	G4 V	7.4
BD+20 1426	G0 V	8.2
L 1246-11	M V	9.0
BD+32 1561	K2-8 V	9.9
* plus bright stars *		. . .
Rho Geminorum 3?	F0 V ? ?	11
BD+18 1563	A0 V	11
Castor 6	A1 V M2-A2 Vm A2-5 V M5-A5 Vm M0.5 Ve M0.5 Ve	11
Alzirr 3?	F5 IV-III ? ?	12
BD+29 1664	G8 V	15
BD+14 512	G5 V	17
BD+18 1074	G5 V	17
BD+37 1738	G5 V	17
BD+30 1423	G5-K3 V	17
71 Orionis 2?	F6 V	18
Psi5 Aurigae	G0 V	18
HR 2208 2?	G2-8 V ?	18
74 Orionis 2?	G V-IV ?	18
Chi Cancri 2?	F6 V ?	19

Other Information

Up-to-date technical summaries on these stars can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARICNS, and the Nearby Stars Database. Additional information may be available at Roger Wilcox's Internet Stellar Database and at 37 Gem in "The Constants and Equations Pages" of Jonathan Stott.

Constellation Gemini, the Twins, is the northernmost of the zodiacal constellations and among the brightest. In Greek mythology, Zeus (the chief of the gods) seduced Leda (the wife of the King of Sparta, Tyndareos) on her wedding night by changing himself into a swan. In time, Leda gave birth to the twin boys immortal Pollux (by Zeus) and mortal Castor (by Tyndareos), and to a girl named Helena who became Queen of Sparta and was abducted by Paris to Troy which led to the Trojan War. The twins, on the other hand, sailed with Jason in the quest for the Golden Fleece; during a storm, they helped save their ship ARGO from sinking, and so the constellation became much valued by sailors. For more information about the stars and objects in this constellation and an illustration, go to Christine Kronberg's Gemini. For another illustration, see David Haworth's Gemini.

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