Summary: A new spectral class of stars, L Dwarfs, has been defined that extends the previously-defined spectral classes of normal stars to cooler objects. 20 new sources have been found in only 1% of the 2MASS data, which was enough to define a temperature sequence with 9 subdivisions for the L spectral class, L0-L8. At least 6 of these sources are brown dwarfs, objects formed like stars but which will never sustain hydrogen burning, and hence will fade from view much more rapidly than normal stars.
The L Dwarfs do not contribute much matter to the Galaxy since they individually weigh typically perhaps one-twentieth the mass of the sun. However, they probably outnumber all other spectral classes of stars combined. This directly implies that there is a good chance that an L dwarf is the closest source to the Solar System, beating out Proxima Centauri, an M5 star 1.3 pc (4.3 light-years) distant. Further 2MASS work will find out whether such a source exists.
The choice of "L" was made from only four available letters that had not previously been used for other types of stars: H, L, T or Y. L was chosen as the closest in the alphabet to "M", the coolest class of stars previously known.
(incomplete) Caltech Press Release (will be replaced with actual press release whenever Caltech gets around to putting it on their website. This is the AP version which is reproduced here since the words originated with us!)
Picture of Chas Beichman, Roc Cutri, Davy Kirkpatrick and Neill Reid at press conference: small (32 KB) and large (80 KB)
Picture of 2MASS L Dwarf in 2MASS, which was accompanied by a POSS Image showing blank sky at that position.
L.A. Times Archive Search - search for "davy kirkpatrick" and cover the day June 11, 1998. Unfortunately, the L.A. Times charges $1.50 to download that story.
In addition, the story was originally on MSNBC, CBS and CNN, but I couldn't find the story at those sites now.
http://spider.ipac.caltech.edu/staff/tchester/2mass/ldwarf_announce/index.html
Comments and feedback: Tom Chester
Last update: 17 October 1998.
