A massive star lights its surroundings - Milky Way star AG Carinae is in luminous blue variable - Brief Article

Science News, June 18, 1994 by Ron Cowen

Shedding mass at a furious rate and shining 1.5 million times more brightly than the sun, the aging Milky Way star AG Carinae is having a final fling. Classified in this phase as a luminous blue variable, AG Carinae is some 50 times more massive than the sun. During this brief, but violent, period, which lasts no more than 100,000 years, the star varies its brightness dramatically and will lose mass equal to as many as four suns.

The starlit gas and dust that surround AG Carinae -- material presumably ejected by it in the past-may offer clues about the mercurial nature of this and other massive stars. But studying this circumstellar material, or nebula, has proven difficult with ground-based telescopes: The nebula is relatively small, faint, and too close to the dazzling light from the star to observe clearly

In imaging the star and its surroundings, a new camera aboard the repaired Hubble Space Telescope has revealed previously unknown structure in the dust. Hubble's wide-field and planetary camera shows that what researchers had interpreted as a jetlike blob of dust is actually a network of bubbles, arches, and filaments, report Antonella Nota and her colleagues at the Space Telescope Science institute in Baltimore. These structures are sculpted and swept up by the star's strong wind.

A major puzzle, says Nota, is how the dust formed and survived. The hot star would seem to sweep aside dust or vaporize it, yet some of the material lies within 1 light-year of AG Carinae. She speculates that the star was considerably cooler in the past and permitted dust to form more easily Nota adds that a disk of gas may surround the star and absorb some of AG Carinae's intense heat. If so, this would shield the dust from imminent destruction.