Orbit of ultra-cool brown dwarf binary (artist's impression)

An international team of astronomers using the world's biggest telescopes have directly measured the mass of an ultra-cool brown dwarf star and its companion star for the first time. Barely the size of the planet Jupiter, the dwarf star weighs in at just 8.5 percent of the mass of our Sun. This is the first ever mass measurement of a dwarf star belonging to a new stellar class of very low mass ultra-cool dwarf stars called L-dwarfs. The observation is a major step towards our understanding of the types of objects that occupy the gap between the lightest stars and the heaviest planets.

In this animation we first see a part of our own Solar System for a size comparison. It is seen that the brown dwarf binary has an orbit slightly smaller than Jupiter?s orbit. We then take a closer look at the individual observations in the order they were made: Hubble/WFPC2 (25 April 2000), Gemini North (7 Feb. 2002), Hubble/ACS (21 Oct. 2002), VLT/NACO (18 Feb. 2003), VLT/NACO (22 Mar. 2003), KECK/NIRC (4 Dec. 2003) and HST/STIS (9 Jan. 2004).