Groombridge 34 AB

NASA -- larger image

Groombridge 34 AB are dim red dwarf stars, like
Gliese 623 A (M2.5V) and B (M5.8Ve) at lower right.
(See a Digitized Sky Survey field image around
Groombridge 34 at the Nearby Stars Database.)

System Summary

Groombridge 34 is located about 11.6 light-years (ly) from our Sun, Sol, in the north central part of (Aab=00:18:22.89+44:01:22.63, B=00:18:25.7+44:01:44:C~, ICRS 2000.0) in Constellation Andromeda, the Chained Maiden -- northwest of the Andromeda galaxy (M 31) and two of its satellite galaxies (M32 and M110). This binary star system was listed by Stephen Groombridge (1755-1834), whose "A Catalog of Circumpolar Stars" was published posthumously in 1838, but its large proper motion was not discovered and measured until 1860. Both visual members of the system are flare stars that have been given the variable star designations GX and GQ Andromedae.

Arnold O. Benz, Institute of Astronomy, ETH Zurich

High resolution and jumbo images (Benz et al, 1998).

Groombridge 34 AB are both flare stars, like UV Ceti
shown flaring at left. UV Ceti is an extreme example
of a flare star that can boost its brightness by five times
in less than a minute, then fall somewhat slower back
down to normal luminosity within two or three minutes
before flaring suddenly again after several hours.

Due to Groombridge 34 AB's proximity to Sol, the ststem has been an object of intense interest among astronomers. It has been selected as "Tier 1" target stars 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 Star A and Star B 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 Groombridge 34 A for evidence of Earth-type life (Lisa Kaltenegger, 2005).

Medialab, © ESA 2002

Larger illustration of
the Darwin Mission.

Astronomers have identified
Groombridge 34 AB as prime targets
for NASA's optical SIM and the ESA's
infrared Darwin missions (Star A).

Groombridge 34 A

This cool and dim, main sequence red dwarf (M1.5 Vne) may have about 48.6 percent of Sol's mass (RECONS), 34 percent of its diameter, and 64/10,000th of its luminosity. The precise orbital elements of Groombridge 34 A and B may be uncertain. Based on photographs taken between 1937 and 1970, Sarah Lee Lippincott reported in 1971 that star A and B are separated by an "average" distance of 147 times the Earth-Sun distance (AU) (of a semi-major axis) in a circular orbit (e= 0.00) of about 2,600 years, in contrast to Josef Hopmann's (1890-1975) earlier report in 1958 of an elliptical orbit (e= 0.25) with an orbital period of 3,000 years and an "average" distance of 157 AU (of a semi-major axis) that varies between 118 and 196 AU. (See an animation of the orbits of Stars A and B and their potentially habitable zones, with a table of basic orbital and physical characteristics.) Some useful catalogue numbers for this star are: GX And, Gl 15 A, Hip 1475, HD 1326 A, BD+43 44 A, SAO 36248, LHS 3, LTT 10108, LFT 31, G 171-47, and ADS 246 A.

Groombridge 34 B

This even cooler and dimmer, main sequence red dwarf star (M3.5 Vne) may have only 16.3 percent of Sol's mass (RECONS), 19 percent of its diameter, and 42/100,000th of its luminosity. Useful catalogue numbers for this star include: GQ And, Gl 15 B, HD 1326 B, BD+43 44 B, G 171-48, LHS 4, LTT 10109, LFT 32, and ADS 246 B.

Hunt for Stellar and Substellar Companions

In 1947, Alfred H. Joy (page 101) reported finding that Groombridge 34 A had an observed range in the radial velocity of 26 km/sec and so may be a spectroscopic binary star. However, no significant velocity variations were detected in subsequent studies (Pettersen and Griffin, 1980; Marcy and Benitz, 1989; and Henry and McCarthy, 1990, last page). A recent search for faint companions to nearby stars using the Hubble Space Telescope's wide field planetary camera found no evidence of a large Jupiter or brown dwarf sized object (Schroeder et al, 2000). Accounting for infrared heating, the distance from either Groombridge 34 A or B where an Earth-type planet would be comfortable with liquid water is around 0.25 AU for Star A and 0.13 AU for Star B.

Life Around a Flare Star

Many dim, red (M) dwarf stars exhibit unusually violent flare activity for their size and brightness. These flare stars are actually common because red dwarfs make up more than half of all starss in our galaxy. Although flares do occur on our Sun every so often, the amount of energy released in a solar flare is small compared to the total amount of energy Sol produces. However, a flare the size of a solar flare occurring on a red dwarf star (such as Groombridge 34 A or B) that is more than ten thousand times dimmer than our Sun would emit about as much or more light as the red dwarf itself, doubling its brightness or more.

Flare stars erupt sporadically, with successive flares spaced anywhere from an hour to a few days apart. A flare only takes a a few minutes to reach peak brightness, and more than one flare can occur at a time. Moreover, in addition to bursts of light and radio waves, flares on dim red dwarfs may emit up to 10,000 times as many X-rays as a comparably-sized solar flare on our own Sun, and so flares would be lethal to Earth-type life on planets near the flare star. Hence, Earth-type life around flare stars may be unlikely because their planets must be located very close to dim red dwarfs to be warmed sufficiently by star light to have liquid water (about 0.08 AU for Groombridge 34 A with a period of 13.5 days or about 0.02 for Groombridge 34 B with a period of 3.8 days), which makes flares even more dangerous around such stars. In addition, the light emitted by red dwarfs may be too red in color for Earth-type plant life to perform photosynthesis efficiently.

Closest Neighbors

The following star systems are located within 10 ly of Groombridge 34.

Star System	Spectra & Luminosity	Distance (light-years)
Ross 248	M4.9-5.5 Ve	1.8
Kruger 60 AB	M3 V M4 V	4.9
EV Lacertae AB	M3.5 Ve ?	6.2
61 Cygni 2	M3.5-5.0 Ve K4.7-7.0 Ve	7.1
Eta Cassiopeiae 2	F9-G0 V K7 V	8.7
Teegarden's Star	M6.5 V	~8.9
L 1159-16	M4.5 Ve	9.0
Van Maanen's Star	DF-G/VII	9.1
Struve 2398 AB	M3.0 V M3.5 V	9.8

Other Information

Up-to-date technical summaries on this star 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.

In Greek mythology, Andromeda was rescued from Cetus, the Whale, by Perseus who also married her. This constellation is most easily seen in Autumn for observers in the Northern Hemisphere, but may be visible from June through February. For more information on stars and other objects in Constellation Andromeda and an illustration, go to Christine Kronberg's Andromeda. For another illustration, see David Haworth's Andromeda.

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