Thuban (Bayer designation: Alpha Draconis or α Dra) is a star in the constellation of Draco. It is located at about 303 light-years away from Earth. It is well known because it was the pole star about 3,900 years ago, when the Earth's north pole pointed close to it.
It is a white to blue-white giant star with about 3.2 times the Sun's mass and 4.9 times its radius. It shines about 240 times brighter and has a surface temperature of about 10,225 Kelvin. Thuban is also a binary star. It has a smaller companion star that orbits every 51 days. The companion star has a radius of 2.326 times and a mass of about 2.431 times.
