A pair of
failed stars takes the record of being the dimmest bulbs ever detected,
astronomers find.
Each of the
substellar objects, called brown
dwarfs, is one million times fainter than the sun in total light on the
electromagnetic spectrum, and at least one billion times fainter in visible
light alone.
A brown
dwarf is a compact ball of gas floating freely in space that's too
cool and lightweight to generate the thermonuclear fusion that powers real
stars, but too warm and massive to be considered a planet.
"These
brown dwarfs are the lowest-power stellar light bulbs in the sky that we know
of," said lead researcher Adam Burgasser, a physicist at MIT.
The
findings were published in the Astrophysical Journal Letters on Dec. 10.
Until now,
astronomers thought this dim duo was a single, faint brown dwarf. Past research
has shown the object is the fifth closest known brown dwarf to us, 17
light-years away toward the constellation Antlia. One light-year is the
distance light will travel in a year, or about 6 trillion miles (10 trillion
kilometers).
Here's how
the team found the singlet was actually twins: They observed the object in
infrared light using NASA's Spitzer Space Telescope. The data showed that what
was still thought to be a single object had a warm atmospheric temperature of
560 to 680 degrees Fahrenheit (293 to 360 degrees Celsius). While this is
hundreds of degrees hotter
than Jupiter, it's still downright cold as far as stars go.
In fact,
the brown dwarfs, called 2MASS J09393548-2448279, or 2M 0939 for short, are
among the coldest brown dwarfs measured so far.
They also
estimated the brightness, which they found to be twice what would be expected
for a brown dwarf with its particular temperature. The solution: The object
must have twice the surface area. So each body shines only half as bright, and
each has a mass of 30 to 40 times that of Jupiter.
Burgasser
said that studying these objects could help astronomers understand details of
brown dwarf structure and evolution.
The work
was funded in part by a NASA grant.
advertisement
