star, meaning that it has a lower proportion of elements with masses greater than helium when compared to the Sun. The temperature, luminosity and surface activity appear to vary slightly in a manner very similar to the sunspot cycle, with a changing duration of 5 to 7 years. The total variability is among the lowest of all stars that have been measured by the Hipparcos spacecraft. Sigma Draconis has a high proper motion, advancing across the celestial sphere at a rate of 1.835 arc seconds per year. The star made its perihelion passage about 46,300 years ago, when it came within . The components of Sigma Draconis'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 the orbit is 10.3 kiloparsecs (about 34,000 light-years). As of 2013, no Jupiter-size or larger companion had been detected about the star and there was no indication of excess infrared radiation that would be evidence of circumstellar matter (such as a debris disk). Planet search Between 2004 and 2013, extensive radial velocity measurements were gathered on Sigma Draconis using the High Resolution Echelle Spectrometer on the Keck Observatory. The Keck/HIRES data indicated a possible period of about 300 days and a likely alias period of 2,800 days. Adding data taken with the Automated Planet Finder at the Lick Observatory strengthened and narrowed the 300-day period while reducing the significance of the 2,800-day period. The combined analysis suggests there may be a Uranus-mass planet on a 308-day orbit, though the authors do not yet consider the discovery to be publishable as they have not yet attempted to rule out other non-planetary explanations for the velocity variations. Notes References External links K-type main-sequence stars Draco (constellation) Draconis, Sigma 7462 BD+69 1053 Draconis, 61 0764 185144 096100 Alsafi