A Star Is Born: R136A Makes Debut

Three astronomers at the University of Wisconsin say they have discovered a star that conventional astronomical theories say cannot exist.

The star--which they have named R136A--is 3500 times more massive than our sun and "by far the largest and brightest star ever found by man," Joseph P. Cassinelli, one of the discovering astronomers said. This is 30 times more massive than any star in our galaxy.

Cassinelli, working with John S. Mathis and Blair D. Savage, discovered R136A last summer using information collected by the International Ultra-Violet Explorer Satellite. The star is located 150,000 light years away inside the gaseous Tarantula Nebula in the Large Magellanic cloud, a neighboring galaxy to the Milky Way. It is surrounded by ultra-violet rays which give the nebula its blue glow.

"It's exciting--normally stars just aren't that big," Margaret J. Geller, assistant professor of Astronomy said Monday, adding that no scientists are sure how such large stars can possibly be formed.

This "superstar" is believed to have the luminosity equivalent to 150 million suns. It burns hydrogen so fast that it emits as much energy in one second as the sun does in five years, Cassinelli said. He added that R136A blasts into space an equivalent of the earth's mass every day at a speed of 7,500,000 miles per hour.

Its temperature of approximately 100,000 degrees Fahrenheit makes its surface ten times as hot as the sun, Cassinelli said.

The International satellite, launched jointly by the National Aeronautics and Space Association and the European Space Agency last year, picked up R136A's ultra-violet spectrum. The fast wind blowing away from it "was incredibly more massive than the solar wind," Cassinelli said.

Until recently, the only information scientists had about this nebula was from its random sightings from the earth's Southern Hemisphere. Recently, it has been resolved to consist of several individual sources of light, but R136A is the first actual star that astronomers have spotted amidst this massive cloud. But some doubts remain among scientists.

"I am still not absolutely convinced that it exists," Lee Hartmann, an astronomer at the Harvard Smithsonian Astrophysical Observatory said Monday. He added that the huge star could actually be a cluster of smaller ones too far away from the earth for observers to differentiate them.

Many astronomers at Harvard share Hartmann's misgivings that the observed phenomenon is a single star. This is partly because the International satellite cannot measure all the star's emitted energy, much of which is sent out as non-visible radiation.

Despite the widespread interest R136A has aroused, one Harvard astronomer says it is really not such a stellar attraction. "It is an interesting curiosity but a bit oversold," David W. Latham, lecturer on Astronomy, said, adding, "it is not the most exciting discovery even in the last two years."

Further exploration of the star or cluster of stars will occur if and when the Space Shuttle--scheduled to take off in April--is put into regular use. The shuttle's telescope will be a better instrument that the satellite for observing R136A, Latham said. "It's possible that we then may be able to tell if it's really one star," he added.