36 Ophiuchi 3?

© Torben Krogh & Mogens Winther,

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

36 Ophiuchi ABC are orange-red
dwarf stars, like Epsilon Eridani
at left center of meteor. (See a
Digitized Sky Survey field image
of 36 Ophiuchi from the
Nearby Stars Database.)

System Summary

This multiple star system is located about 19.5 light-years away in the southernmost part (17:15:20.98-26:36:10.19, ICRS 2000.0) of Constellation Ophiuchus, the Serpent Holder or Snake Charmer -- south of Theta Ophiuchi. The system appears to be composed of three stars, of which Star C orbits the much closer binary pair of Stars AB. The existence of an unseen but massive substellar, fourth component around star B is now thought to be unlikely.

36 Ophiuchi A

A main sequence orange-red dwarf (K0-1 Ve), the primary has only around 85 percent of Sol's mass (RECONS estimate), 81 percent of its diameter (Johnson and Wright, 1983, page 689), 28 percent of its luminosity, and 50 to 98 percent of Sol's abundance of elements heavier than hydrogen (metallicity), based on its abundance of iron (Cayrel de Strobel et al, 1991, page 301). The orbital distance where an Earth-type planet would have liquid water is centered around 0.54 AU -- just beyond Mercury's orbital distance in the Solar System -- where a planet's period would be about 167 days or over one third of an Earth year. Based on an average parallax (0.1675") incorporating Hipparcos data, stars A and B are separated "on average" by about 88 AUs (of a semi-major axis) in a highly eccentric orbit (e= 0.922) that swings between seven and 169 AUs and takes around 570 years to complete (Irwin et al, 1996 -- "Orbit 4") and (Peter Brosche, 1960). (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 star catalogue numbers include: 36 Oph, HR 6402, Gl 663 A, Hip 84405, HD 155886, CD-26 12026, CP(D)-26 5858, SAO 185198, LHS 437, and ADS 10417 A.

36 Ophiuchi B

A main sequence orange-red dwarf (K1-5 Ve), star B has only about 85 percent of Sol's mass (RECONS estimate), 81 percent of its diameter (Johnson and Wright, 1983, page 689), 27 percent of its luminosity, and 1.2 to 2.5 times Sol's abundance of elements heavier than hydrogen (metallicity), based on its abundance of iron (Cayrel de Strobel et al, 1991, page 301). The orbital distance where an Earth-type planet would have liquid water is centered around 0.53 AU -- just beyond the orbital distance of Mercury in the Solar System -- where the orbital period would be almost 163 days, or over a third of an Earth year. Some useful star catalogue numbers include: HR 6401, Gl 663 B, HD 155885, SAO 185199, LHS 438, and ADS 10417 B.

36 Ophiuchi Bb?

Radial velocity variations would suggest that star B has a substellar companion of about eight times the mass of Jupiter in an orbit of about 30 to 100 years to complete. However, the highly elliptical orbit of the binary pair which brings stars A and B as close together as 6.8 AUs makes the orbit of such a superplanet improbable, as the maximum stable orbit implies an "average" orbital distance of about 1.5 AUs (of a semi-major axis) and a period about two years for an object with no more than two Jupiter-masses. Hence, the velocity variations are likely due to the high chromospheric activity of stars A and B (Irwin et al, 1996).

36 Ophiuchi C

A main sequence orange-red dwarf (K5-6 Ve), star C has only about 71 percent of Sol's mass (RECONS estimate), 72 percent of its diameter (Johnson and Wright, 1983, page 689), 8.7 percent percent of its luminosity, and 46 to 100 percent of Sol's abundance of elements heavier than hydrogen (metallicity), based on its abundance of iron (Cayrel de Strobel et al, 1991, page 301). It orbits the AB pair from around 4,370 to 5,390 AUs away and is a variable star. The orbital distance where an Earth-type planet would have liquid water is centered around 0.30 AU -- three fourths of Mercury's orbital distance of in the Solar System -- where the orbital period would be over 76 days. Some useful star catalogue numbers include: Gl 663 C, Gl 664, Hip 84478, HD 156026, CD-26 12036, CP(D)-26 5863, SAO 185213, and LHS 439.

Closest Neighbors

The following star systems are located within 10 ly of 36 Ophiuchi.

Star System	Spectra & Luminosity	Distance (light-years)
CD-32 13297	M2 V	3.0
MLO 4 ABC	K3-4 V K5 V M2.5 V	4.5
Wolf 630 A-C	M2.5 Ve M4.5 Ve M7 V	6.3
CD-44 11909	M3.5-5 V	6.4
Wolf 629 AB	M3.5 V ?	6.8
BD-12 4523 AB	M3.0 V ?	7.5
CD-46 11540	M2.5-3 V	7.6
G 154-44	M4.5 V	8.2
CD-40 9712	M0-3 V	8.6

Other Information

Up-to-date technical summaries on individual stars can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARICNS entry for Star A, Star B, Star C, 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.

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). Aescupapius 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.

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