Andrew Yee[_1_]
June 13th 07, 05:24 PM
Bob Naeye
Goddard Space Flight Center, Greenbelt, Md. May 28, 2007
301-286-4553
NASA's FUSE Satellite Catches Collision of Titans
Using NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite and
ground-based telescopes, astronomers have determined, for the first time,
the properties of a rare, extremely massive, and young binary star system.
The system, known as LH54-425, is located in the Large Magellanic Cloud, a
satellite galaxy of our Milky Way. The binary consists of two O-stars, the
most massive and luminous types of stars in the Universe.
Spectra obtained by Georgia State University astronomer Stephen Williams at
the 1.5-meter (4.9 foot) telescope at the Cerro Tololo Inter-American
Observatory in Chile show that the two stars contain about 62 and 37 times
the mass of our Sun. "The stars are so close to each other -- about
one-sixth the average Earth-Sun distance -- that they orbit around a common
center of mass every 2.25 days," says Williams' colleague Douglas Gies of
Georgia State University, Atlanta. With a combined mass of about 100 suns,
the system is one the most extreme binaries known. The stars are probably
less than 3 million years old.
Each star blows off a powerful stellar wind, and FUSE's observations have
provided the first details of what happens when the two supersonic winds
collide. The wind collision zone wraps around the smaller star and produces
a curved surface of superheated gases that emit X-rays and far-ultraviolet
radiation. FUSE is ideal for these measurements because the lines that best
indicate the properties of stellar winds show up in the far ultraviolet part
of the spectrum, where FUSE is most sensitive.
FUSE project scientist George Sonneborn of NASA Goddard Space Flight Center,
Greenbelt, Md., is presenting these results today in a poster at the spring
2007 American Astronomical Society meeting in Honolulu, Hawaii.
The more massive star is shedding material at a rate of 500 trillion tons
per second (about 400 times greater than the rate the sun loses mass through
the solar wind), with a speed of 5.4 million miles per hour. The smaller
star is ejecting mass at about one-tenth the rate of its sibling. The mass
loss rate of both stars is consistent with other single stars having the
same temperature and luminosity.
As the stars age and swell in size, they will begin to transfer substantial
amounts of mass to each other. This process could begin in a million years.
The stars are orbiting so close to each other that they are likely to merge
as they evolve, producing a single extremely massive star like the more
massive member of the Eta Carinae binary system. Eta Carinae is one of the
most massive and luminous stars in the Milky Way Galaxy, with perhaps 100
solar masses.
"The merger of two massive stars to make a single super star of over 80 suns
could lead to an object like Eta Carinae, which might have looked like
LH54-425 one million years ago," says Sonneborn. "Finding stars this massive
so early in their life is very rare. These results expand our understanding
of the nature of very massive binaries, which was not well understood. The
system will eventually produce a very energetic supernova."
"These stars are evolving in the blink of an eye compared to the sun, which
has looked pretty much the same for over 4 billion years," adds Rosina Iping
of the Catholic University, Washington and NASA Goddard, leader of the team
that observed LH54-425 with FUSE. "But this binary looks totally different
from Eta Carinae even though there is maybe only one million years
difference in age. These massive stars zoom through their life cycle really
fast. Will this binary system produce something like Eta Carinae? We don't
know."
Launched in 1999, FUSE is a NASA Explorer mission developed in cooperation
with the French and Canadian space agencies by Johns Hopkins University,
University of Colorado, and University of California, Berkeley. NASA's
Goddard Space Flight Center, Greenbelt, Md., manages the program.
[NOTE: Images supporting this release are available at
http://www.nasa.gov/centers/goddard/news/topstory/2007/fuse_titans.html ]
Goddard Space Flight Center, Greenbelt, Md. May 28, 2007
301-286-4553
NASA's FUSE Satellite Catches Collision of Titans
Using NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite and
ground-based telescopes, astronomers have determined, for the first time,
the properties of a rare, extremely massive, and young binary star system.
The system, known as LH54-425, is located in the Large Magellanic Cloud, a
satellite galaxy of our Milky Way. The binary consists of two O-stars, the
most massive and luminous types of stars in the Universe.
Spectra obtained by Georgia State University astronomer Stephen Williams at
the 1.5-meter (4.9 foot) telescope at the Cerro Tololo Inter-American
Observatory in Chile show that the two stars contain about 62 and 37 times
the mass of our Sun. "The stars are so close to each other -- about
one-sixth the average Earth-Sun distance -- that they orbit around a common
center of mass every 2.25 days," says Williams' colleague Douglas Gies of
Georgia State University, Atlanta. With a combined mass of about 100 suns,
the system is one the most extreme binaries known. The stars are probably
less than 3 million years old.
Each star blows off a powerful stellar wind, and FUSE's observations have
provided the first details of what happens when the two supersonic winds
collide. The wind collision zone wraps around the smaller star and produces
a curved surface of superheated gases that emit X-rays and far-ultraviolet
radiation. FUSE is ideal for these measurements because the lines that best
indicate the properties of stellar winds show up in the far ultraviolet part
of the spectrum, where FUSE is most sensitive.
FUSE project scientist George Sonneborn of NASA Goddard Space Flight Center,
Greenbelt, Md., is presenting these results today in a poster at the spring
2007 American Astronomical Society meeting in Honolulu, Hawaii.
The more massive star is shedding material at a rate of 500 trillion tons
per second (about 400 times greater than the rate the sun loses mass through
the solar wind), with a speed of 5.4 million miles per hour. The smaller
star is ejecting mass at about one-tenth the rate of its sibling. The mass
loss rate of both stars is consistent with other single stars having the
same temperature and luminosity.
As the stars age and swell in size, they will begin to transfer substantial
amounts of mass to each other. This process could begin in a million years.
The stars are orbiting so close to each other that they are likely to merge
as they evolve, producing a single extremely massive star like the more
massive member of the Eta Carinae binary system. Eta Carinae is one of the
most massive and luminous stars in the Milky Way Galaxy, with perhaps 100
solar masses.
"The merger of two massive stars to make a single super star of over 80 suns
could lead to an object like Eta Carinae, which might have looked like
LH54-425 one million years ago," says Sonneborn. "Finding stars this massive
so early in their life is very rare. These results expand our understanding
of the nature of very massive binaries, which was not well understood. The
system will eventually produce a very energetic supernova."
"These stars are evolving in the blink of an eye compared to the sun, which
has looked pretty much the same for over 4 billion years," adds Rosina Iping
of the Catholic University, Washington and NASA Goddard, leader of the team
that observed LH54-425 with FUSE. "But this binary looks totally different
from Eta Carinae even though there is maybe only one million years
difference in age. These massive stars zoom through their life cycle really
fast. Will this binary system produce something like Eta Carinae? We don't
know."
Launched in 1999, FUSE is a NASA Explorer mission developed in cooperation
with the French and Canadian space agencies by Johns Hopkins University,
University of Colorado, and University of California, Berkeley. NASA's
Goddard Space Flight Center, Greenbelt, Md., manages the program.
[NOTE: Images supporting this release are available at
http://www.nasa.gov/centers/goddard/news/topstory/2007/fuse_titans.html ]