Supernova close-up, mini-galaxies star in Hubble presentation

January 17, 1991|By Luther Young | Luther Young,Sun Staff Correspondent

PHILADELPHIA -- Astronomers working around the shortcomings of the Hubble Space Telescope reported their latest results yesterday, including the first glimpse deep into the heart of a globular cluster of stars, a close-up of a developing supernova and a precise distance measurement to a nearby galaxy that could help pin down the age of the universe.

But they also pointedly told those attending the 177th American Astronomical Society meeting that such success doesn't mean the $1.5 billion orbiting telescope shouldn't be repaired as planned in 1993 to correct for its serious mirror flaw.

"All of our problems can't be solved by software [changes]," said F. Duccio Macchetto, lead scientist for Hubble's Faint Object Camera.

Despite that not-so-subtle message to the budget-strapped National Aeronautics and Space Administration, scientific teams with four of the five instruments aboard reported that they had bypassed the telescope's diminished capabilities to make significant discoveries.

Among the more exciting were observations of massive stars, rTC including Eta Carinae, 8,000 light-years from Earth in the southern Milky Way with a mass 100 times that of the sun.

The star "has a lot of history," said astronomer Jeff Hester of the California Institute of Technology: In 1833, it suddenly became the second brightest star in the sky, then faded to its present glow just on the edge of naked-eye visibility.

Dr. Hester used Hubble's Wide-field/Planetary Camera to offer a close-up of the star. Indications are that Eta Carinae -- probably the most massive star in our galaxy -- is in an unstable state that may portend a supernova explosion. A supernova explosion represents the death throes of a massive star that has exhausted its nuclear fuel.

According to astronomer Sally Heap of NASA's Goddard Space Flight Center, another massive star -- known as Melnick 42, about 170,000 light-years away in the Large Magellanic Cloud -- also appears to be evolving toward a supernova state within the next few million years. Her observations with Hubble's High Resolution Spectrograph revealed that the star was shedding hot gases at a furious rate in a "stellar wind" that strips it of mass equal to the whole sun every 100,000 years. The hot, young supergiant is more than a million times brighter than the sun, she said.

Other Hubble results included the first look into the core of globular clusters, dense spherical "mini-galaxies" of nearly a million stars each scattered about the Milky Way in a loose halo. The stars are the oldest in the galaxy. In the heart of a cluster known as M15, 42,000 light-years away, astronomers Tod Lauer and Sandra Faber found evidence that the dense core had avoided collapse into a black hole -- once thought inevitable for massive systems -- by evolving tightly bound binary stars that transferred energy back out of the core to other stars through gravitational interactions.

And Dr. Nino Panagia of the Space Telescope Science Institute reported using Hubble's Faint Object Camera to determine a precise distance -- 169,000 light-years -- to the glowing ring of gas left over from the 1987 supernova explosion.

"It's the first step to determine the cosmological distance scale, and thus the age of the universe, with a high degree of accuracy," he said.

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