Omicron Draconis

Omicron Draconis (Latinised as ο Draconis, abbreviated to ο Dra) is a giant star in the constellation Draco located 322.93 light years from the Earth. Its path in the night sky is circumpolar for latitudes greater than 31o north, meaning the star never rises or sets when viewed in the night sky.



This is a single-lined spectroscopic binary system, but the secondary has been detected using interferometry. It is an RS Canum Venaticorum variable system with eclipses. The total amplitude of variation is only a few hundredths of a magnitude. The secondary star is similar to the Sun, presumably a main sequence star, while the primary is a giant star 25 times larger than the Sun and two hundred times more luminous.

Identities as pole star
Omicron Draconis can be considered the north pole star of Mercury, as it is the closest star to Mercury's north celestial pole. In addition to that, this star is currently the Moon's north pole star, which occurs once every 18.6 years. The pole star status changes periodically, because of the precession of the Moon's rotational axis.