IC 418: The “Spirograph” Nebula
Glowing like a multi-faceted jewel, the planetary nebula IC 418 lies
about 2,000 light-years from Earth in the direction of the
constellation Lepus. This photograph is one of the latest from
NASA’s 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 center 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 0.1 light-year. The stellar remnant at the center 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 billions of
years as a white dwarf. Our own Sun is expected to undergo a similar
fate, but fortunately this will not occur until some 5 billion years
from now.
The Hubble image of IC 418 is shown in a false-color representation,
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 ionized nitrogen (the
coolest gas in the nebula, located furthest from the hot nucleus),
green shows emission from hydrogen, and blue traces the emission
from ionized oxygen (the hottest gas, closest to the central star).
The remarkable textures seen in the nebula are newly revealed by
the Hubble telescope, and their origin is still uncertain.
Image Credit: NASA and The Hubble Heritage Team (STScI/AURA)
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