Eta Car/ACIS

The Hot Heart of the Little Man

A star named Eta Carinae may be the most massive star in the Galaxy; it's certainly one of the most unusual stars. Barely 150 years ago it stood as one of the brightest objects seen from earth; then it "erupted", throwing off a huge amount of material (about twice as much as in our entire solar system) in a short amount of time. Dust quickly formed in this ejecta, and this dust shroud currently obscures the star from view. The ejecta forms a famous cloud around the star, called the "homunculus nebula" since, in ground-based telescopes, the cloud looks like a stick figure of a little man, though from space, the cloud is resolved into an hourglass shape. One of the first observations made by the Chandra X-ray Observatory was of this famous star. The Chandra observation (above) improves on earlier EINSTEIN observatory and ROSAT X-ray images, in particular clearly show the bright point of extremely hot X-rays at the heart of the homunculus, and also the extended emission which surrounds the star like a broken ellipse. Astronomers think that the extended emission may have been produced by an eruption of the star which took place about 500-1000 years ago; they think the bright hot gas at the core of the star is produced by the collision of the strong stellar wind from Eta Car with an unseen companion.

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Page Author: Dr. Michael F. Corcoran
Last modified August 18, 2000