Sigma Draconis

Star type
g KO

Distance from Earth
g 18.78 ly

Star Service No.
g NA

Age
g At least 8 Gyr (other sources say 5-7 Gyr)

Diameter/Mass/Temp (xSol)
g 79%; 80%; 5,196 K - The temperature of this star appear to vary slightly in a manner very similar to the sunspot cycle, although the full length of this cycle has not yet been determined.

Brightness (xSol)
g 39%; The temperature and surface activity of this star appear to vary slightly in a manner very similar to the sunspot cycle, although the full length of this cycle has not yet been determined.

Metallicity
g Only about 56% to 59% percent of Sol's abundance of iron; super-rich metal star

Comparison to Sol
g See chart (similar to Alpha Centauri B)

Picture of star
g NA

Star system features
g Star has a visual companion which is not gravitationally bound to it
g Galactic orbit similar to Sol’s

Known planets
g No brown dwarf or large Jupiter- or Saturn-mass object in a "torch" orbit

Habitable zone
g An Earth-type planet would be "comfortable" with liquid water centered around 0.62 AU - inside the orbital distance of Venus in the Solar System - where a planet would have an orbital period of only about 199 days, or over half an Earth year. Due to star’s low luminosity, an Earth-like planet would be about 2e-10 times as bright as the star at optical wavelengths. Turnbull and Tarter consider it the nearest interesting SETI target. Porto de Mello lists it as one of 13 nearby astrobiologically interesting stars.
g No indication of excess infrared radiation that would be evidence of circumstellar matter (such as a debris disk).

Orbital map
g NA

View from star
g See sky map

Nearby stars
(Star systems with 10 light years)
g LP 44-113: 3.2 ly
g BD+68 946 AB: 5 ly
g LP 71-165: 5.7 ly
g BD+61 2068 AB: 5.8 ly
g AC+65 6955: 7.6 ly
g Chi Draconis 2: 7.9 ly
g Struve 2398 AB: 7.9 ly
g Kruger 60 AB: 8.3 ly
g V1581 Cygni 2: 8.3 ly
g AC+79 3888: 8.6 ly
g G 227-29: 9 ly
g AC+54 1646-56: 9.3 ly
g BD+56 2966: 9.5 ly

Map locating star system
g See stellar map (listed as “Sigma Dra”)

Location in Earth sky
g In the northwestern part of Constellation Draco, the Dragon, south of Tyl (Epsilon Draconis) and north of Altais or Nodus Secundus (Delta Draconis)

Other names
g Alsafi
g NSV 12176
g Sig Dra
g CSV 101868
g 61 Dra
g HR 7462
g Gl 764 (or is it Gliese 780?)
g Hip 96100
g HD 185144
g BD+69 1053
g SAO 18396
g LHS 477
g LTT 15713
g LFT 1486

Sci-fi mentions
g Honor Harrington series of novels by David Weber. The Honorverse version of the Sigma Draconis system includes the technologically advanced planet Beowulf, adjacent to a wormhole.
g Rollback by Robert J. Sawyer. Central to this 2007 novel are signals received in 2009 and 2049 from Sigma Draconis.
g "Spock's Brain", episode of Star Trek (TOS) television series. Planets III, IV and VI of Sigma Draconis are all Class M, capable of supporting human life, but III and IV are still incapable of interstellar space flight, while VI is in an ice age; a visit to VI reveals that the planet once supported a civilization with very high technology.
g Total Eclipse (Doubleday, 1974) by John Brunner has several missions to the third planet during the years 2020-2028 by the Stellaris, a ship that can travel through "qua-space"
g Mentioned in in Robert Silverberg's novel "The Man in the Maze"

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