From the March 2015 issue

Web Extra: Brown dwarfs take center stage

Brown dwarfs are so faint that astronomers didn’t find one until the 1990s. Some even qualify as our next-door neighbors.
By | Published: March 30, 2015 | Last updated on May 18, 2023
Luhman 16A and B
In 2013, scientists discovered Luhman 16A and B, a pair of brown dwarfs that has taken over the title for the third-closest star system to the Sun.
NASA/JPL-Caltech/Gemini Observatory/AURA/NSF
In the two decades since astronomers discovered the first brown dwarf — Teide 1 in the Pleiades star cluster — they have found more than a thousand. These enigmatic objects, which don’t have enough mass to ignite hydrogen fusion and thus become full-fledged stars, glow mostly by radiating the heat from their formation. Because they are so faint, all those that lurk in the solar neighborhood escaped detection until the 21st century.

The table below lists all known brown dwarfs within 15 light-years of Earth. These objects are classified as L, T, or Y, running from hottest to coolest. The nearest — a pair of objects dubbed Luhman 16A and B some 6.6 light-years away — rank as the fifth and sixth closest objects to home. Only the triple-star system Alpha Centauri and Barnard’s Star are nearer. One final note: A fine line exists between the smallest hydrogen-burning stars and the largest brown dwarfs, so it is quite possible that a few M-class “stars” not listed here are actually brown dwarfs.

        Name Distance      Right
Declination Class    Year of
 Luhman 16A      6.6    10h49.3m     –53°19′  L8      2013
 Luhman 16B      6.6    10h49.3m     –53°19′  T1      2013
 WISE 0855-0714      7.2      8h55.2m       –7°15′  Y      2014
 WISE 1506+7027     11.1    15h06.8m       70°28′  T6      2011
 Epsilon Indi B    11.8    22h04.2m      –56°47′  T1      2003
 Epsilon Indi C    11.8    22h04.2m      –56°47′  T6      2003
 WISE 0350-5658    12.1      3h50.0m      –56°59′  Y1      2011
 SCR 1845-6357 B     12.6    18h45.0m      –63°58′  T6      2006
 UGP 0722-0540    13.4      7h22.5m        –5°41′  T9      2010

Distance  in light-years; Right ascension and declination in 2000.0 coordinates.