This image, taken by NASA's Hubble Space Telescope, shows the colorful
"last hurrah" of a star like our Sun. 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 planetary
nebulae because through small telescopes they resembled the disks of the
distant planets Uranus and Neptune. The planetary nebula in this image 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 400,000 degrees
Fahrenheit (200,000 degrees Celsius). 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 image was taken Feb. 6, 2007 with Hubble's Wide Field Planetary Camera
2. The colors correspond to material expelled by the star. Blue
corresponds to helium; blue-green to oxygen; and red to nitrogen and
hydrogen.
