SIGMA DRACONIS

'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".

Contents

Properties

See also

References

External links

Properties

The star is an orange main sequence dwarf of spectral type K0. 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.^[1]
The temperature, luminosity 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. The total variability of this star is among the lowest of all stars
that have been measured by the Hipparcos spacecraft.¹
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).¹
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).^[2]

See also

★ Sigma Draconis in fiction

References

1. Astrobiologically Interesting Stars Within 10 Parsecs of the Sun, Porto de Mello, Gustavo; del Peloso, Eduardo F.; Ghezzi, Luan, , , Astrobiology, 1999
2. A Survey of Nearby Main-Sequence Stars for Submillimeter Emission, E. K. Holmes, H. M. Butner, S. B. Fajardo-Acosta, L. M. Rebull, , , The Astronomical Journal, 2003

External links

★ Sigma Draconis