Brown Dwarfs (3) ...
Brown dwarfs are very difficult to find. One way to look for them is to search for
low-mass companions in binary star systems as candidates, and then to establish that the companions are
brown dwarfs by examining the detailed characteristics of the low-mass object. The
methods used are the
same as those used in searching for planets around other stars: find a
small wobble in the proper motion of
the primary star, or variations in the Doppler shift of lines from the primary star
that indicate the
gravitational effect of the companion, and then try to study the spectrum of the companion.
Methane Dwarfs
A second approach is to look for individual brown dwarfs
by examining large fields of stars for ones that
are unusually red and dim, and then among those
possibilities to examine the spectra for brown dwarf
characteristics. Recently, several brown dwarf
candidates have been found by the Sloan Digital Sky Survey. The first
is shown in the top right figure (the faint red smudge between the arrows).
Because the presence of methane in the spectrum was used to confirm that
this is not a star, it has been termed a methane dwarf.
