Washington: NASA's Chandra X-ray Observatory
has found a "cannibal" star which is believed to have eaten up
a companion star or planet, a discovery that provides new
insight into how stars and the planets around them may
interact as they age.
The star identified as BP Piscium (BP Psc) appears to be
a more evolved version of the Sun but surrounded by a dusty
and gaseous disk.
Located about 1,000 light years from Earth, the star is
found with a pair of jets several light years long blasting
out of the system in opposite direction.
While the disk and jets are characteristics of a very
young star, astronomers believe BP Psc is an old star in its
so-called red giant phase.
These are in fact remnants of a recent and catastrophic
interaction whereby a nearby star or giant planet was consumed
by the star, the scientists said in a paper appeared in 'The
Astrophysical Journal Letters'.
According to them, when stars like the Sun begin to run
out of nuclear fuel, they expand and shed their outer layers.
For example, the Sun is expected to swell so that it nearly
reaches or possibly engulfs Earth, as it becomes a red giant
star.
Joel Kastner of the Rochester Institute of Technology,
who led the Chandra study, said: "It appears that BP Psc
represents a star-eat-star Universe or maybe a tar-eat-planet
one. Either way, it just shows it's not always friendly out
there."
The Chandra X-ray Observatory is a satellite launched by
NASA in 1999. It was named after Indian-American physicist
Subrahmanyan Chandrasekhar, who is known for determining the
maximum mass for white dwarfs.
Several pieces of information have led astronomers to
rethink how old BP Psc might be. The star is not located near
any star-forming cloud, and its atmosphere contains only a
small amount of lithium. And its surface gravity also appears
to be too weak for a young star and instead matches up with
one of an old red giant.
"It seems that BP Psc has been energised by its meal,"
said co-author Rodolfo Montez Jr, also from the Rochester
Institute of Technology.
The star's surface is obscured throughout the visible and
near-infrared bands, so the Chandra observation represents the
first detection at any wavelength of BP Psc itself.
"BP Psc shows us that stars like our Sun may live quietly
for billions of years," said co-author David Rodriguez from
UCLA, "but when they go, they just might take a star or planet
or two with them."
A new paper using observations with the Spitzer Space
Telescope has reported possible evidence for a giant planet in
the disk surrounding BP Psc. This might be a newly formed
planet or one that was part of the original planetary system.
"Exactly how stars might engulf other stars or planets is
a hot topic in astrophysics today," said Kastner.
"We have many important details that we still need to
work out, so objects like BP Psc are really exciting to find."
PTI
First Published: Wednesday, September 15, 2010, 15:30