Wednesday, October 8, 1997
Most powerful star discovered
RESEARCH: Scientists at UCLA detect body to be largest known
By Hannah Miller
Daily Bruin Senior Staff
First a Nobel Prize, then the most powerful star in the
universe. In the second UC science coup this week, UCLA researchers
have discovered a massive heavenly body called the "Pistol Star"
that could measure up to 279 million miles in diameter.
Led by a 31-year-old UCLA graduate and utilizing one of the most
cutting-edge techniques in the field of astronomy, the team set out
in 1993 to investigate the center of the galaxy.
With the help of NASA’s Hubble Space Telescope, they could see
beyond the clouds of Earth’s atmosphere.
And the star they found, first sighted in 1995 but not studied
since, had 10 million times the energy of our sun.
"Personally, I thought that this was a massive star," said Dr.
Don F. Figer, the team’s leader. "I was happy to receive
confirmation of that."
And it is huge. It releases as much energy in 6 seconds as the
sun does in a year. At its birth, it could have been the most
massive star to have ever existed. And if you placed the Pistol
Star at the center of our solar system, it would engulf our sun –
as well as the orbits of Mercury, Venus, Earth and Mars.
The images produced by the five researchers show the star
suspended within a bright, pistol-shaped nebula, a gaseous cloud
from which the star gets its name. The image adds support to
Figer’s theory that the star produced the nebula. He says more
study of both will yield insights into star formation and
evolution.
The technique that they used to make all these judgements,
infrared imaging, has only come into widespread use in the last few
years. It has the potential to register images where visible-light
photography can’t.
"The star was found (with ground-based telescopes), but we had
to be able to take a picture with very good resolution," said Dr.
Ian McLean, a UCLA professor of astronomy and physics. Infrared was
the only imaging technique that could take such a picture.
"The center of the galaxy is impossible to see without
infrared," said McLean. "There’s too much dust blocking it, like a
smoke screen."
That interstellar dust is made up of tiny particles suspended in
space. They block all visible light coming from the Pistol Star;
the most powerful telescopes on Earth cannot see the star.
But there seems to be some dissent about the findings.
Roberta Humphreys, an astronomy professor at the University of
Minnesota, thinks the findings may be a bit overstated. She says
the Pistol Star appears to be "comparable in luminosity and
probably initial mass to Eta Carinae."
That’s a star visible in the Southern hemisphere that’s the most
massive, luminous star in Earth’s region of the Milky Way.
Humphreys isn’t convinced from the new images that the Pistol
Star is a single star.
"They don’t have sufficient resolution to see if that’s one star
or two or three – and it could be at that distance," she said.
Hubble captured the images on Sept. 13 and 14. Figer and his
colleagues were so excited by what they saw, they released the
images Tuesday before they could publish their findings.
Researchers estimate the Pistol Star is 25,000 light-years from
Earth, near the center of the Milky Way galaxy. It’s invisible to
the eye because interstellar dust absorbs most of the light it
gives off.
Figer suggested back in 1995 that the Pistol Star may have
created the surrounding nebula by throwing off its layers.
Based on the new pictures, Figer said, "It’s pretty clear this
gas (of the nebula) came from an eruption from the star," that
occurred 4,000 to 6,000 years ago.
The Pistol Star appears to be scheduled for a short, violent
life. The star will "die" with a brilliant supernova in 1 to 3
million years. In comparison, our sun, burning slower and colder,
is expected to last another 5 billion years.
With reports from Daily Bruin wire services.