A huge ball of brightly burning gas drifting through a
neighboring galaxy may be the heaviest star ever discovered -
hundreds of times more massive than the sun, scientists said
Wednesday after working out its weight for the first time.
Those behind the find say the star, called R136a1, may once have
weighed as much as 320 solar masses. Astrophysicist Paul Crowther
said the obese star - twice as heavy as any previously discovered -
has already slimmed down considerably over its lifetime.
In fact it's burning itself off with such intensity that it
shines with nearly 10 million times the luminosity of the sun.
"Unlike humans, these stars are born heavy and lose weight as
they age," said Crowther, an astrophysicist at the University of
Sheffield in northern England.
"R136a1 is already middle-aged and has undergone an intense
weight loss program."
Crowther said the giant was identified at the center of a star
cluster in the Tarantula Nebula, a sprawling cloud of gas and dust
drifting through one of the Milky Way's neighboring galaxies.
The star was the most massive of several giants identified by
Crowther and his team in an article in the Monthly Notices of the
Royal Astronomical Society.
While other stars can be larger, notably the swollen
crimson-colored ones known as red giants, they weigh far less.
Still, the mass of R136a1 and its ilk means they're tens of
times bigger than our sun, and that they're brighter and hotter,
too.
Surface temperatures can surpass 40,000 degrees Celsius (72,000
degrees Fahrenheit), seven times hotter than the sun. They're also
several million times brighter, a product of the fact that the
greedy giants tear through their energy reserves far faster than
their smaller counterparts.
That also means that massive stars live fast and die young,
quickly shedding huge amounts of material and burning themselves
out in what are thought to be spectacular explosions.
"The biggest live only 3 million years," Crowther said. "In
astronomy that's a very short time."
Small lifespans are one of several reasons why these obese stars
are so hard to find. Another is that they're extremely rare,
forming only in the densest star clusters.
Astronomers also have a limited range in which to look: In
clusters that are too far away it isn't always possible to tell if
a telescope has picked up on one heavyweight star or two smaller
ones in close proximity.
In this case, Crowther's team re-examined previously known stars
to see if they could find an accurate measurement of their weight.
The team reviewed archival data from the Hubble Space Telescope and
gathered new readings from the European Southern Observatory's Very
Large Telescope at Paranal in Chile.
Scientists who weren't involved in the find said the results
were impressive, although they cautioned it was still possible,
although unlikely, that scientists had confused two very close
stars for a bigger, single one.
"What they're characterizing as a single massive star could in
fact be a binary system too close to be resolved," said Mark
Krumholz, an astronomer at the University of California, Santa
Cruz.
Both he and Phillip Massey, an astronomer with the Lowell
Observatory in Arizona, also cautioned that the star's weight had
been inferred using scientific models and that those were subject
to change.
But both scientists said the authors had made a strong case,
arguing for instance that the solar material being thrown off from
feuding stars in a binary system would produce much more powerful
X-rays than have been detected.
Crowther acknowledged that R136a1 could have a partner, but he
said it was likely to be a much smaller star, meaning that its
birth weight was still considerable - perhaps 300 solar masses
instead of 320.
neighboring galaxy may be the heaviest star ever discovered -
hundreds of times more massive than the sun, scientists said
Wednesday after working out its weight for the first time.
Those behind the find say the star, called R136a1, may once have
weighed as much as 320 solar masses. Astrophysicist Paul Crowther
said the obese star - twice as heavy as any previously discovered -
has already slimmed down considerably over its lifetime.
In fact it's burning itself off with such intensity that it
shines with nearly 10 million times the luminosity of the sun.
"Unlike humans, these stars are born heavy and lose weight as
they age," said Crowther, an astrophysicist at the University of
Sheffield in northern England.
"R136a1 is already middle-aged and has undergone an intense
weight loss program."
Crowther said the giant was identified at the center of a star
cluster in the Tarantula Nebula, a sprawling cloud of gas and dust
drifting through one of the Milky Way's neighboring galaxies.
The star was the most massive of several giants identified by
Crowther and his team in an article in the Monthly Notices of the
Royal Astronomical Society.
While other stars can be larger, notably the swollen
crimson-colored ones known as red giants, they weigh far less.
Still, the mass of R136a1 and its ilk means they're tens of
times bigger than our sun, and that they're brighter and hotter,
too.
Surface temperatures can surpass 40,000 degrees Celsius (72,000
degrees Fahrenheit), seven times hotter than the sun. They're also
several million times brighter, a product of the fact that the
greedy giants tear through their energy reserves far faster than
their smaller counterparts.
That also means that massive stars live fast and die young,
quickly shedding huge amounts of material and burning themselves
out in what are thought to be spectacular explosions.
"The biggest live only 3 million years," Crowther said. "In
astronomy that's a very short time."
Small lifespans are one of several reasons why these obese stars
are so hard to find. Another is that they're extremely rare,
forming only in the densest star clusters.
Astronomers also have a limited range in which to look: In
clusters that are too far away it isn't always possible to tell if
a telescope has picked up on one heavyweight star or two smaller
ones in close proximity.
In this case, Crowther's team re-examined previously known stars
to see if they could find an accurate measurement of their weight.
The team reviewed archival data from the Hubble Space Telescope and
gathered new readings from the European Southern Observatory's Very
Large Telescope at Paranal in Chile.
Scientists who weren't involved in the find said the results
were impressive, although they cautioned it was still possible,
although unlikely, that scientists had confused two very close
stars for a bigger, single one.
"What they're characterizing as a single massive star could in
fact be a binary system too close to be resolved," said Mark
Krumholz, an astronomer at the University of California, Santa
Cruz.
Both he and Phillip Massey, an astronomer with the Lowell
Observatory in Arizona, also cautioned that the star's weight had
been inferred using scientific models and that those were subject
to change.
But both scientists said the authors had made a strong case,
arguing for instance that the solar material being thrown off from
feuding stars in a binary system would produce much more powerful
X-rays than have been detected.
Crowther acknowledged that R136a1 could have a partner, but he
said it was likely to be a much smaller star, meaning that its
birth weight was still considerable - perhaps 300 solar masses
instead of 320.
