Sigma Draconis

Starbox begin
name=Sigma Draconis Starbox observe
epoch=J2000
constell=Draco
ra=RA|19|32|21.5908cite web
url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NSV%2012176&protocol=html
title=SIMBAD Query Result: NSV 12176 -- Variable Star
publisher=Centre de Données astronomiques de Strasbourg
accessdate= 2007-06-15 ]
dec=DEC| +69|39|40.232
appmag_v=4.70 Starbox character
class=K0 V
b-v=0.79cite web
url=http://www.ari.uni-heidelberg.de/aricns/cnspages/4c01582.htm
title=ARICNS 4C01582
publisher=Astronomisches Rechen-Institut, Heidelberg
accessdate= 2007-06-15 ]
u-b=0.38
variable=None Starbox astrometry
radial_v=26.7
prop_mo_ra=598.26
prop_mo_dec=-1738.71
parallax=173.40
p_error=0.46
parallax_footnote=
absmag_v=5.87 Starbox detail
age=3.3 × 10⁹
gravity=4.60cite journal
last=Hearnshaw | first=J. B.
title=Carbon and iron abundances for twenty F and G type stars
journal=Astronomy and Astrophysics
year=1974 | volume=36 | pages=191–199
url=http://adsabs.harvard.edu/abs/1974A&A....36..191H
accessdate=2007-06-14 ]
metal= [Fe/H] =−0.23
mass=0.87
radius=0.778±0.008cite web
author=Boyajian, Tabetha S. "et al" | date=2008-04-17
url=http://arxiv.org/abs/0804.2719
title=Angular Diameters of the G Subdwarf µ Cassiopeiae A and the K Dwarfs σ Draconis and HR 511 from Interferometric Measurements with the CHARA Array
publisher=arXiv.org | accessdate=2008-07-03 ]
rotation=1.5 km/scite journal
author=Gray, David F.; Baliunas, Sallie L.; Lockwood, G. W.; Skiff, Brian A.
title=The activity cycle of Sigma Draconis
journal=Astrophysical Journal
year=1992 | volume=400 | issue=2 | pages=681–691
url=http://adsabs.harvard.edu/abs/1992ApJ...400..681G
accessdate=2007-07-12 | doi=10.1086/172030]
luminosity=0.428±0.013
temperature=5,196 Starbox catalog
names=σ Draconis, 61 Draconis,
HD 185144, HR 7462, BD+69°1053, GCTP 4607.00, GJ 764, LHS 477, and HIP 96100.

Sigma Draconis (σ Dra / σ Draconis) is a star 18.8 light-years away from Earth. Its traditional name is Alsafi. It is in constellation Draco. Its visual magnitude is 4.68.

The traditional name "Alsafi" (also Athafi) supposedly derives from an Arabic word "al-athafi" "the cooking tripods". This refers to the tripods used by nomads for open-air cooking [cite book
first=Richard Hinkley | last=Allen | year=1963
title=Star Names, Their Lore and Meaning | publisher=Dover
location=New York | isbn=0-486-21079-0 ]

Properties

The star is an orange main sequence dwarf of spectral type K0. The radius of this star has been directly measured using interferometery with the CHARA Array, which yields a result of 77.8% of the Sun's radius. The projected rotation rate of this star ($v\; sin\; i$) is relatively low at 1.5 km/s. It is considered a slightly metal-poor star; meaning it has a lower proportion of isotopes with more mass than Helium when compared to the Sun.cite journal
author=Porto de Mello, Gustavo; del Peloso, Eduardo F.; Ghezzi, Luan
title=Astrobiologically Interesting Stars Within 10 Parsecs of the Sun
journal=Astrobiology | year=1999 | volume=6
issue=2 | pages=308–331
url=http://adsabs.harvard.edu/abs/2005astro.ph.11180P
accessdate=2007-02-04
doi=10.1089/ast.2006.6.308 ]

The temperature, luminosity and surface activity of thisstar appear to vary slightly in a manner very similar to the
sunspot cycle, although the full length of this cyclehas not yet been determined. The total variability of this star is among the lowest of all starsthat have been measured by the Hipparcos spacecraft.

The components of this star's space velocity are U=+36, V=+40 and W=-10 km/s. This gives the star an unusually large orbital eccentricity about the Milky Way galaxy of 0.30 (compared to 0.06 for the Sun.) The mean galactocentric distance for this orbit is 10.3 kiloparsecs (about 34,000 light-years).

No Jupiter-size or larger companion has yet been detected about this star and there is no indication of excess
infrared radiation that would be evidence of circumstellar matter (such as a debris disk). [cite journal
author=E. K. Holmes, H. M. Butner, S. B. Fajardo-Acosta, L. M. Rebull
title=A Survey of Nearby Main-Sequence Stars for Submillimeter Emission
journal=The Astronomical Journal | year=2003
volume=125 | issue=6 | pages=3334–3343
url=http://adsabs.harvard.edu/abs/2003AJ....125.3334H
accessdate = 2007-07-12 | doi=10.1086/375202]

ee also

* Sigma Draconis in fiction

References

External links

* cite web
url=http://www.solstation.com/stars/sigdraco.htm
title=Sigma Draconis | publisher =SolStation
accessdate = 2007-06-15