|Volume: 05, Issue: 09||02/14/2007|
The Colorful Demise of a Sun-Like StarA new image from NASA’s Hubble Space Telescope shows the colorful “last hurrah” of a star like our sun. The picture on the top left was taken February 6, 2007, by Hubble’s Wide Field and Planetary Camera 2, which was designed and built by NASA’s Jet Propulsion Laboratory, Pasadena, California.
The star is ending its life by casting off its outer layers of gas, which formed a cocoon around the star’s remaining core. Ultraviolet light from the dying star makes the material glow. The burned-out star, called a white dwarf, is the white dot in the center. Our sun will eventually burn out and shroud itself with stellar debris, but not for another 5 billion years.
Our Milky Way galaxy is littered with these stellar relics, called planetary nebulae. The objects have nothing to do with planets. Eighteenth- and nineteenth-century astronomers named them that because through small telescopes they resembled the disks of the distant planets Uranus and Neptune.
The planetary nebula in the image at the top left is called NGC 2440. The white dwarf at the center of NGC 2440 is one of the hottest known, with a surface temperature of nearly 200,000 degrees Celsius (400,000 degrees Fahrenheit). The nebula’s chaotic structure suggests that the star shed its mass episodically. During each outburst, the star expelled material in a different direction. This can be seen in the two bow tie-shaped lobes. The nebula also is rich in clouds of dust, some of which form long, dark streaks pointing away from the star. NGC 2440 lies about 4,000 light-years from Earth in the direction of the constellation Puppis.
The colors in the image correspond to material expelled by the star. Blue corresponds to helium; blue-green to oxygen; and red to nitrogen and hydrogen.
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