Discovery of the Nearest L Dwarf: The Intrinsically Faintest Object at Visual Wavelengths Known Beyond Our Solar System

As part of an ongoing search for Earth’s nearest stellar neighbors, astronomers have determined the distance to a stellar-like body known as DEN 0255-477 and discovered that it is the nearest-known L dwarf. This body is now also the faintest object outside our solar system for which its intrinsic visual brightness has been measured.

The new record holder is nearly 100 million times fainter than the Sun. It is located only 16.2 light-years (4.97 parsecs) from Earth, making DEN 0255-4700 the 48th nearest known system of stars or brown dwarfs. This very reddish object is a third closer to Earth than the next known L dwarf, which is 24 light-years away. The discovery by a team led by Edgardo Costa and Rene Mendez of the Universidad de Chile in Santiago will be published in the September 2006 issue of the Astronomical Journal.

The Sun’s new neighbor has a formal spectral type of L7.5 V, indicative of a cool object with a temperature of only 2,600 degrees F (1700 K). This is rather cooler than the least massive stars, which have temperatures of 4,000 F (2500 K). A spectrum of DEN 0255-4700 shows that it has exotic elements such as potassium, rubidium, and cesium in its outer atmosphere, mixed with superheated water.

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