Difference between revisions of "Sigma Draconis"
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| − | '''Sigma Draconis''' is a nearby star located in the constellation of [[Draco]]. | + | {{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''". | + | 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. | + | 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. | + | 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. | + | 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]] | |
| − | |||
| − | |||
Latest revision as of 14:45, August 14, 2018
| Sigma Draconis | |
|---|---|
| Observational Data | |
| Designation | HD 185144 HIP 96100 |
| Right ascension | 19h 32m 21.5899s[1] |
| Declination | +69° 39′ 40.236″[1] |
| Constellation | Draco |
| Type of object | Red dwarf |
| Magnitude | Apparent Mag: +4.68[1] Absolute Mag: +5.87[2] |
| Astrometry | |
| Distance from Earth | 18.8 ly[3] |
| Radial velocity | 26.78±0.08 km/s[1] |
| Proper motion | RA: 597.482 mas/yr[1] Dec.: -1,738.313 mas/yr[1] |
| Parallax | 173.77±0.18 mas[1] |
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.[1]
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.[4]
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.[5] 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 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.
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Sigma Draconis from the SIMBAD Astronomical Database
- ↑ From definition of absolute magnitude, using apparent magnitude (+4.68) and distance (18.8 ly) given here.
- ↑ Calculated from given parallax of 173.77 mas.
- ↑ Allen, Richard Hinkley (1963). Star Names, Their Lore and Meaning. New York: Dover. ISBN 0-486-21079-0. Avaliable online at: penelope.uchicago.edu
- ↑ 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. Bibcode:2001A&A...367..521P