Going Out with a Bang


ngc2392_2NGC 2392 is the remains of a star similar to our Sun located about 4,200 light years from Earth. AKA the Eskimo Nebula, it is what astronomers call a planetary nebula. Planetary nebulas actually have nothing to do with planets. The term is leftover from when these objects looked like planetary disks to astronomers using small optical telescopes.

Planetary nebulas form when a star has used up all of the hydrogen in its core, an event roughly 5 billion years off for the Sun. When that happens, the star begins to cool off and puff outward, increasing to tens or hundreds of times its original diameter. Eventually, the star’s outer layers are whisked away by a strong solar wind moving at tens of thousand of km per hour, leaving the hot core with a surface temperature on the order of 50,000 °C. The core then begins throwing off its outer layers in an even faster wind a speed in the millions of km per hour. The radiation from the hot star and the interaction of its fast wind with the slower wind creates the complex shell of a planetary nebula. In the end, the remnant star will collapse to become a white dwarf.

This composite image of NGC 2392 contains X-ray data from the Chandra X-ray Observatory in purple showing the location of million-degree gas near the center of the planetary nebula. Data from the Hubble Space Telescope (colored red, green, and blue) show the outer layers ejected from the star. The filament-like structures form when the faster wind and radiation from the central star interact with cooler dust and gas earlier ejected from the star.

Image Credit: NASA