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THE PISTOL STAR

The sun, a relatively dim bulb by celestial standards, cannot hold a candle to the "Pistol star." This behemoth, identified by astronomers using NASA's orbiting Hubble Space Telescope may be the brightest star known.

Spewing out as much energy in six seconds as the sun does in one year, the Pistol star is up to 10 million times more powerful than the sun and spans the diameter of Earth's orbit. Don F. Figer, who headed the team from University of California at Los Angeles that recorded the images, says, "This star may have been more massive than any other star, and now it is without question still among the most massive."

When the titanic star was formed one to three million years ago, it may have weighed up to 200 times the mass of the sun. Since then, it has shed much of its mass in violent eruptions, which may have created the pistol-shaped nebula that surrounds it. The astronomers estimate that the star ejected up to 10 times the mass of the sun in giant outbursts about 4,000 and 6,000 years ago. It will continue to lose more material, eventually revealing its bare, hot core, sizzling at 100,000 degrees Fahrenheit at the surface.

Burning at such a dramatic rate, the Pistol Star is destined for certain death in a brilliant supernova in one to three million years. "Massive stars are burning their candles at both ends, burning out quickly and often creating dramatic events, such as exploding as supernovae," says Mark Morris, a U.C.L.A. co-investigator.

Pistol Star is approximately 25,000 light-years from Earth near the center of the Milky Way galaxy. It is not visible to the eye but is located in the direction of the constellation Sagittarius, hidden behind the great dust clouds along the Milky Way. "It is perhaps no accident that this extreme-mass star is found near the center of the galaxy," Morris says. "Current evidence leads us to believe that the star-formation process there may favor stars much more massive than our modest sun, and it appears that the Pistol star is at the top of the heap among its ponderous peers."

The most powerful telescopes cannot see the Pistol star in visible wavelengths. But 10 percent of the infrared light leaving the Pistol star reaches Earth, putting it within reach of infrared telescopes, such as the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on board Hubble. This false-colored image is a composite of two separately filtered images taken with the NICMOS on September 13, 1997. The field of view is 4.8 light-years across, at the star's distance of 25,000 light-years.


Image: DON F. FIGER, UCLA and NASA

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