A team of
astronomers has found a cold object that is neither star nor planet circling a
star relatively close to Earth.
The object,
a cool
brown dwarf orbiting its red parent star, sits about 12.7 light-years from
the Sun, making it the third closest such object known to date, researchers
said.
Cold and
dim, brown
dwarfs are objects that are typically more massive than planets but fall
short of igniting into full-fledged stars. Astronomers using the Very Large
Telescope at European Southern Observatory in Paranal, Chile found
the latest brown dwarf orbiting the red star SCR
1845-6357.
"Besides
being extremely
close to Earth, this object is a T dwarf--a very cool brown dwarf--and the
only such object found as a companion to a low-mass star," said Beth Biller,
lead author of the study reporting brown dwarf find and a graduate student at
the University of Arizona, in a statement. "It is also likely the brightest
known object of its temperature because it is so close."
The
newly found brown dwarf carries a temperature of about 1,382 degrees Fahrenheit
(750 degrees Centigrade) and a mass between nine and 65 times that of Jupiter,
researchers said. It also orbits its red parent at a distance 4.5 times that of
the average separation between Earth and the Sun, or about 418 million miles
(672 million kilometers), they added.
The
research will be detailed in an upcoming issue of the Astrophysical Journal.
Despite
their proximity, the red star and brown dwarf observed by Biller and her
colleagues is not the closest to Earth. Two
others have been found around the star Epsilon Indi, which sits about 11.8
light-years from Earth. Another
object sits slightly further out, at a distance of about 13 light-years,
followed by another brown dwarf 16 light-years from Earth.
One
light-year is the distance light travels in one year, about 5.88 trillion miles
(9.7 trillion kilometers). The nearest star to Earth is Proxima
Centauri 4.2-light-years away.
Biller
and her team hope their brown dwarf will help astronomers better understand the
cold objects that seem to occupy a purgatory between stellar and planetary
formation.
Last
year, researchers found a brown dwarf surrounded
by a disk of material, hinting that the odd objects could spawn their own system of
mini-worlds.
Markus
Kasper, an ESO team member who participated in the recent brown dwarf study,
said the new find allows astronomers
to pin down the object's brightness and--after further observations--its precise
mass.
"These
properties are vital for understanding the nature of brown dwarfs," Kasper
said.
advertisement
