Becoming a star can be a challenge. But new observations reveal
that it's much easier in space than in Hollywood. Only about 14%
of all aspiring celestial stars fizzle out, researchers report.
In principle, it's easy to deduce how many stars succeed: just
compare the numbers of normal stars with the number of failed
stars, also known as brown dwarfs. These flops are born with
less than 8% of the sun's mass, so their centers never heat up
enough to sustain the nuclear fusion of hydrogen-1, the isotope
that powers so-called main-sequence stars like the sun. Most
brown dwarfs do burn hydrogen-2, or deuterium, but it soon runs
out, and all nuclear reactions cease. When young, a brown dwarf
glows red—chiefly from the heat of its birth—and then cools and
fades as it ages. That makes them hard to find—and thus hard to
know whether they're rare or as plentiful as full-fledged stars.
Astronomer J. Davy Kirkpatrick of the California Institute of
Technology in Pasadena and colleagues decided to take a look at
infrared w