Spirograph Nebula (IC 418)

The planetary nebula IC 418 lies about 2000 light-years from Earth in the direction of the constellation Lepus. This photograph is from the NASA/ESA Hubble Space Telescope, obtained with the Wide Field Planetary Camera 2.

A planetary nebula represents the final stage in the evolution of a star similar to our Sun. The star at the centre of IC 418 was a red giant a few thousand years ago, but then ejected its outer layers into space to form the nebula, which has now expanded to a diameter of about 0.2 light-years.

The stellar remnant at the centre is the hot core of the red giant, from which ultraviolet radiation floods out into the surrounding gas, causing it to fluoresce. Over the next several thousand years, the nebula will gradually disperse into space, and then the star will cool and fade away for millions of years as a white dwarf.

Our own Sun is expected to undergo a similar fate, but fortunately this will not occur until some 5000 million years from now.

This Hubble image of IC 418 is shown in false-colour, based on Wide Field Planetary Camera 2 exposures taken in February and September 1999, through filters that isolate light from various chemical elements.

Red shows emission from ionised nitrogen (the coolest gas in the nebula, located furthest from the hot nucleus), green shows emission from hydrogen, and blue traces the emission from ionised oxygen (the hottest gas, closest to the central star).

The origin of the remarkable textures revealed by Hubble is still uncertain.
Acknowledgment: R. Sahai (JPL) and A. Hajian (USNO)