THE SUN HAS TWO NEW NEIGHBOURS in the form of brown dwarf stars estimated to be only 15 and 18 light-years from the Solar System.
This puts them very close indeed. The closest known star to the Sun is Proxima Centauri, slightly more than 4 light-years away. The closest known brown dwarfs (known as Epsilon Indi Ba and Bb) are about 12 light-years away.
Brown dwarfs are halfway between big planets are fully-fledged stars. They’re often called ‘failed stars’, since during their formation they could not accumulate enough mass to ignite the natural nuclear fusion reactor in their core that is the long-living energy source of stars.
Ralf-Dieter Scholz and colleagues at the Leibniz Institute for Astrophysics Potsdam (AIP) used recently published data from the NASA satellite WISE (Wide-field Infrared Survey Explorer) for their discovery.
On the move
The two new neighbours—named WISE J0254+0223 and WISE J1741+2553— attracted attention by the extreme contrast between their strong brightness at infrared wavelengths and their almost invisible appearance at optical wavelengths.
In addition, both objects have been measured to move at relatively high speed across the sky, and their current positions are noticeably different compared with earlier observations.
High speed is usually a good indication that objects are close to the observer.
The AIP team used the Large Binocular Telescope (LBT) in Arizona, USA, to more accurately determine the spectral type and distance of the brighter of the two dwarfs.
Both objects belong to the coolest class of brown dwarfs, the T-type, which are just on the borderline of the predicted but not yet well-defined class of Y-type ultracool brown dwarfs.
No hotter than an oven
It is presumed that most brown dwarfs have cooled to around the temperature of an oven, about 230 degrees Celsius … and maybe even as cool as the temperature at the surface of the Earth.
The search for these elusive neighbours of the Sun is currently in full swing.
Scientists say it is possible that we are surrounded by ultracool brown dwarfs in similar high numbers as normal stars, and that our nearest known neighbour will soon be a brown dwarf rather than Proxima Centauri.
Adapted from information issued by the Leibniz Institute for Astrophysics Potsdam. Images: brown dwarf illustration, ESO/L. Calçada; LBT, AIP, LBT Observatory; WISE images, AIP, NASA/IPAC Infrared Science Archive.
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