Orbit of AB Doradus C

The orbit of AB Doradus C around its more massive companion, AB Doradus A, is shown as a green ellipse. AB Doradus takes 11.75 years to make a full orbit, the separation on the sky being only ~0.2 second of arc. This orbital solution (which implies a mass of 0.09 solar mass for AB Doradus C) was obtained from Hipparcos/VLBI astrometry, and is confirmed by the last 5 AO images obtained by the present team. AB Doradus is a system of 2 pairs of stars (four stars in total: a quadruple system), lying 48 light-years away towards the Doradus constellation (the Swordfish). AB Doradus A is the young major member of this system and has a faint companion, AB Dor C, just 3 astronomical units (AU) away, or three times the distance between the Earth and the Sun. In our Solar System, this would be within the asteroid belt between the orbits of Mars and Jupiter. AB Dor C was imaged for the first time, thanks to ESO's VLT, in 2005 (ESO Press Release eso0503). The other members of the system are the pair AB Doradus BaBb (also first imaged in the previous work of 2005) located 133 AU from AB Dor A. While AB Doradus A has a mass about 85 % that of the Sun, AB Doradus C is almost 10 times less massive than AB Doradus A and belongs to the category of cool red dwarfs.