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Line 1: − + + + + + + + + + + + + + + + + − + − + − + − + + + + + − + − ==References== − {{reflist}}
Add Template:Night Sky and Template:Stars, tidy up references
'''Sigma Draconis''' is a nearby star located in the constellation of [[Draco]]. The star is one of the closest to our [[Sun]], at only 18.8 light years away. Even though it is an orange class K star, because of its relative close distance the star is visible to the unaided eye under very dark skies, with an apparent magnitude of 4.68.<ref>http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NSV%2012176&protocol=html</ref>
{{Night Sky
| image =
| designation =HD 185144<br/>HIP 96100
| rightascension =19<sup>h</sup> 32<sup>m</sup> 21.5899<sup>s</sup><ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=sigma+draconis&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id Sigma Draconis] from the [http://simbad.u-strasbg.fr/simbad SIMBAD Astronomical Database]</ref>
| declination =+69° 39′ 40.236″<ref name=simbad/>
| distance =18.8 ly<ref>Calculated from given [[parallax]] of 173.77 mas.</ref>
| constellation =Draco
| type =Red dwarf
| dimensions =
| magnitude =Apparent Mag: +4.68<ref name=simbad/><br/>Absolute Mag: +5.87<ref>From definition of absolute magnitude, using apparent magnitude (+4.68) and distance (18.8 ly) given here.</ref>
| redshift =
| radvelocity =26.78±0.08 km/s<ref name=simbad/>
| propmotion =RA: 597.482 mas/yr<ref name=simbad/><br/>Dec.: -1,738.313 mas/yr<ref name=simbad/>
| parallax =173.77±0.18 mas<ref name=simbad/>
}}
'''Sigma Draconis''' is a nearby star located in the constellation of [[Draco]]. The star is one of the closest to our [[Sun]], at only 18.8 light years away. Even though it is an orange class K star, because of its relative close distance the star is visible to the unaided eye under very dark skies, with an [[star magnitude|apparent magnitude]] of 4.68.<ref name=simbad/>
Sigma Draconis' traditional name is '''Alsafi''', which is derived from the Arabic word ''athafi'' (or ''Athafiyy''), meaning "''the cooking tripods''". This is in reference to the tripods desert nomads used for cooking in the open-air.<ref>Allen, Richard Hinkley (1963). Star Names, Their Lore and Meaning. New York: Dover. ISBN 0-486-21079-0.</ref>
Sigma Draconis' traditional name is '''Alsafi''', which is derived from the Arabic word ''athafi'' (or ''Athafiyy''), meaning "''the cooking tripods''". This is in reference to the tripods desert nomads used for cooking in the open-air.<ref>Allen, Richard Hinkley (1963). Star Names, Their Lore and Meaning. New York: Dover. ISBN 0-486-21079-0. Avaliable online at: [http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Draco*.html penelope.uchicago.edu]</ref>
Sigma Draconis is an orange-red dwarf star on the main sequence of spectral class K0 V. The star has some 89 percent of our Sun's mass, and some 79 percent of its diameter, but is only 39 percent as luminous.<ref>http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001A%26A...367..521P&db_key=AST&data_type=HTML&format=&high=4378fcfeea24447</ref> The star's [[metallicity]] is only some 56 to 59 percent that of out [[Sun]], based on the abundance of [[iron]].
Sigma Draconis is an orange-red dwarf star on the main sequence of spectral class K0 V. The star has some 89 percent of our Sun's mass, and some 79 percent of its diameter, but is only 39 percent as luminous.<ref>Pasinetti Fracassini, L., Pastori, L., Covino, S. and Pozzi, A. (2001). Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) -Third edition -Comments and statistics. ''Astronomy and Astrophysics'', 367(2), pp.521-524. [https://ui.adsabs.harvard.edu/#abs/2001A%26A...367..521P Bibcode:2001A&A...367..521P]</ref> The star's [[metallicity]] is only some 56 to 59 percent that of out [[Sun]], based on the abundance of [[iron]].
So far all searches using radial velocity techniques, conducted by the Lick Planet Search, to locate substellar companions around Sigma Draconis have failed to find any [[brown dwarf]] or large [[gas giant]] very near to the star. For an [[terrestrial planet|Earth-like]] world to have liquid water on its surface, the orbit would need to be around 0.62 AU, somewhat less than the orbit of [[Venus]]. At this time such a world is about impossible to detect.
So far all searches using [[radial velocity]] techniques, conducted by the Lick Planet Search, to locate substellar companions around Sigma Draconis have failed to find any [[brown dwarf]] or large [[gas giant]] very near to the star. For an [[terrestrial planet|Earth-like]] world to have [[liquid]] [[water]] on its surface, the [[orbit]] would need to be around 0.62 AU, somewhat less than the orbit of [[Venus]]. At this time such a world is about impossible to detect.
Currently Sigma Draconis is considered a high priority target for the both the future NASA's [[Terrestrial Planet Finder]] and the ESA's Darwin probe when they are launched around 2015. These probes will search for rocky worlds in the [[habitable zone]] of Sigma Draconis and other stars.
Currently Sigma Draconis is considered a high priority target for the both the future NASA's [[Terrestrial Planet Finder]] and the [[ESA]]'s Darwin probe when they are launched around 2015. These probes will search for rocky worlds in the [[habitable zone]] of Sigma Draconis and other stars.
==References==
{{reflist}}
{{Stars}}
[[Category:Astronomy]]
[[Category:Astronomy]]
[[Category:Stars]]