V2133 / 12 Ophiuchi

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© Torben Krogh & Mogens Winther,

(Amtsgymnasiet and EUC Syd Gallery,
student photo used with permission)

12 Ophiuchi is an orange-red
dwarf star, like Epsilon Eridani
at left center of meteor. (See
a Digitized Sky Survey image
of 12 Ophiuchi from the
Nearby Stars Database.)

System Summary

12 Ophiuchi is located about 31.9 light-years (ly) away from our Sun, Sol, within the east central corner (16:36:21.4-2:19:28.5, ICRS 2000.0) of Constellation Ophiuchus, the Serpent Holder or Snake Charmer -- near Yed Prior (Delta Ophiuchi) and Yed Posterior (Epsilon Ophiuchi), and south of Marfik (Lamda Ophiuchi) and north of Zeta Ophiuchi. The star may be visible to many Humans without a telescope. As 12 Ophiuchi 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 12
Ophiuchi as a prime target for the
Terrestrial Planet Finder (TPF),
now planned for launch between
2014 and 2020.

The Star

12 Ophiuchi is a main-sequence orange-red dwarf star of spectral and luminosity type K0-2 Ve. The star may have around 90 percent of Sol's mass, 85 to 100 percent of its diameter (Perrin and Karoji, 1987, page 236; and Johnson and Wright, 1983, page 687), and around 39 percent of its luminosity. It appears to be as enriched than Sol in elements heavier than hydrogen ("metals") with about 102 percent of Sol's abundance of iron (Cayrel de Strobel et al, 1991, page 300).

The SIMBAD Astronomical Database identifies 12 Ophiuchi as a BY Draconis-type variable star -- whose variability is attributed to stellar rotation in which starspots covering a significant fraction of the stellar surface rotate in and out of the field of view -- with the designation of V2133 Ophiuchi. According to the Yale Bright Star Catalogue, 1991 5th Revised Edition notes entry for HR 6171, the star has a rotational period of 11 days based on observation of its starspots and is deficient in ultraviolet wavelengths. Useful star catalogue numbers for 12 Ophiuchi include: V2133 Oph, 12 Oph, HR 6171*, Gl 631, Hip, 81300, HD 149661, BD-01 3220, BD-02 4211, SAO 141269, FK5 1433, LHS 3224, LTT 6632, LFT 1294, and LPM 614.

Hunt for Substellar Companions

Using the radial velocity technique pioneered by Geoffrey W. Marcy and R. Paul Butler, the Lick Planet Search for substellar companions has thus far failed to find a brown dwarf or large Jupiter- or Saturn-mass object in a "torch" orbit around 12 Ophiuchi (Cumming et al, 1999). On the other hand, the distance from 12 Ophiuchi where an Earth-type planet would be "comfortable" with liquid water is centered around only 0.64 AU -- inside the orbital distance of Venus in the Solar System -- where a planet probably would have an orbital period around half 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 12 Ophiuchi. 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 12 Ophiuchi.

Star System	Spectra & Luminosity	Distance (light-years)
GJ 1207	M3.5 V	2.7
LP 625-34	M V	5.0
Wolf 635	K5 V	5.5
L 989-20 AB	G-M3.5 V ?	6.1
Wolf 636	M0-3.5 V	6.4
Hip 84581	?	6.5
BD+05 3409 A?	M1 V	8.8
BD+02 3312	K7 V	9.3

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 and at www.alcyone.de's entry for V2133 Ophiuchi.

One story is that the Ancient Greeks named this constellation after Aesculapius (the first doctor, a son of Apollo and Coronis, and grandfather of Hippocrates, the famous Greek physician). Aesculapius was killed by Zeus at the urging of Hades for threatening to make mankind immortal like the gods by bringing the dead back to life. In admiration of the doctor's skills, however, Zeus raised the doctor and the serpent from which he had first learned the medicinal usefulness of certain herbs into the heavens. Located along the equatorial region of the sky, Ophiuchus is one of the larger constellations. For more information on stars and objects in this constellation and an illustration, go to Christine Kronberg's Ophiuchus. For another illustration, see David Haworth's Ophiuchus.

Note: Nominated as a "notable nearby star" by Mike Stevens.