Eta Car optical and X-ray image
Credit: X-ray: M. F. Corcoran & NASA; optical: Nathan Smith, Jon Morse, & NASA

Will Doomed Star Doom Us Too?

Stars live as long as they have nuclear fuel. Stars eventually run out of fuel, and if the star is massive enough, it may explode. Massive stars also run through their fuel more quickly than stars of lower mass. One of the fastest burning stars is named Eta Carinae. Eta Car is thought to be one of the most massive stars in our Galaxy, and one of the most unstable. The image above is a composite of an optical image from the Hubble Space Telescope (in red and blue) and an X-ray image from the Chandra X-ray Observatory (in white, yellow and green). The star itself is the bright point of light at the center of the image, while the bubble-shaped optical nebula was produced by an eruption of the star in the 19th century. Farther out there is an irregular nebula, which is surrounded by a broken ellipse of X-ray emitting gas. Even though Eta Car is about 8000 light years from earth, the explosion of the star may pose a threat to life on earth, if it explodes. But stellar evolution is sufficiently uncertain, especially for extremely massive stars, that no one really knows whether Eta Car will explode in its present, "Luminous Blue Variable" state, or whether it will need to enter a new stage of its evolution sometime in the future before it goes bang. But a new study suggests that we may be living on borrowed time. A massive variable star called SN 2009ip an eruption similar to Eta Car's "Great Eruption" in the 1840's. The brightness variations of this star were so powerful it was initially believed the star was destroyed, but subsequent observations showed the star survived somehow. At least it survived until last week, when new observations showed that SN 2009ip had exploded to become a "real" supernova (though some question this conclusion). SN 2009ip exploded only 3 years after the start of its transient phase, while Eta Car has survived for nearly two centuries after it's "Great Eruption". Is Eta Car overdue for an explosion?
Published: September 24, 2012

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