Cat's Eye Nebula
Credit: X-ray: NASA/UIUC/Y.Chu et al., Optical: NASA/HST

Sparkle in the Cat's Eye

As stars like the sun age they use up their nuclear fuel. As the fuel runs low, the innermost regions of the star will contract due to the weight of the overlying stellar material. As the central regions contract, the outer regions expand and the star becomes much bigger and brighter, a so-called "red giant". Since the star is essentially going two ways at once, there may come a point at which the outer parts of the star become disconnected from the inner parts; the outer parts can become so disconnected that they leave the star entirely and form an extensive cloud of gas around the star. This gas cloud is called a "planetary nebula" (because in small telescopes some of these nebula appear as resolved disks, as do the real planets in our solar system). Though planetary nebula have been seen for hundreds of years, the mechanism by which the stellar atmosphere detaches itself and expands into space is not yet understood. Now theChandra X-ray Telescope has added another piece to the puzzle. The image on the left is an X-ray image of the "Cat's Eye" planetary nebula obtained by the Chandra ACIS camera, at the same spatial scale as the optical image. Chandra reveals the central star as a bright point source of high temperature X-rays. This is the first time astronomers have seen such X-ray emission from the central star of a planetary nebula. Chandra shows that the "bubbles" around the central star contain extremely hot, million-degree gas which also glows bright in X-rays. The image above right is a Hubble Space telescope image of the "Cat's Eye". The swirls of colorful gas emphasize the complex nature of the ejection of the stellar envelope. The Chandra image is superposed on the Hubble image to show where the X-ray emitting gas is located among the bright optical swirls of gas.

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Page Author: Dr. Michael F. Corcoran
Last modified June 14, 2001