Figure 1: Artist’s impression of a brown dwarf.
With an estimated 0.086 ± 0.009 times the Sun’s mass, DE0630-18 is at the stellar/substellar mass boundary, so it is either a very low-mass star or a brown dwarf. DE0630-18 is estimated to be located ~60 light-years away. Using the FORS2 optical camera on the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in northern Chile, J. Sahlmann et al. (2015) report the discovery of a brown dwarf in a 3-year orbit around DE0630-18.
By precisely tracking the motion of DE0630-18 relative to a field of reference stars over a period of 1209 days between 7 December 2010 and 30 March 2014, DE0630-18 was found to “wobble” in a way that suggests the presence of an unseen companion in orbit around it. The magnitude of the wobbling indicates that the gravitational mass of the unseen companion around DE0630-18 is either ~0.060 or ~0.075 times the Sun’s mass, in the brown dwarf mass-regime.
This newfound object is designated DE0630-18B, with the suffix “B” indicating its secondary nature. The method by which the presence of DE0630-18B was detected is known as astrometry. DE0630-18 and its companion DE0630-18B make up either a brown dwarf / brown dwarf binary system or a very low-mass star (DE0630-18) / brown dwarf (DE0630-18B) binary system.
Figure 2: Motion of DE0630-18 relative to the field of reference stars. J. Sahlmann et al. (2015).
J. Sahlmann et al. (2015), “Astrometric planet search around southern ultracool dwarfs III. Discovery of a brown dwarf in a 3-year orbit around DE0630-18”, arXiv:1504.02469 [astro-ph.SR]