Image Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA), R. Sahai and J. Trauger (Jet Propulsion Laboratory)
Kohoutek 4-55 (or K 4-55 for short) is a planetary nebula with a size of about 100 x 165 light-years, located nearly 4600 light-years from Earth in the northern constellation of Cygnus (the Swan). It is named after its discoverer, the Czech astronomer Lubos Kohoutek who discovered many planetary nebulae during the 1970s.
Despite their name, planetary nebulae have nothing to do with planets. The name of planetary nebulae arose because of the visual similarity between some round planetary nebulae and the planets Uranus and Neptune when viewed through early telescopes.
When a star with a mass up to eight times that of the Sun runs out of fuel at the end of its life, it blows off its outer shells and begins to lose mass. This allows the hot, inner core of the star (collapsing from a red giant to a white dwarf) to radiate strongly, causing this outward-moving cocoon of gas to glow brightly.
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.
In the case of K 4-55, a bright inner ring is surrounded by a bipolar structure. The entire system is then surrounded by a faint red halo, making Kohoutek 4-55 look like a giant cosmic eye. This multi-shell structure is fairly uncommon in planetary nebulae.
This image is taken with the Wide Field Planetary Camera 2 onboard the Hubble Space Telescope on May 4, 2009. The colors represent the makeup of the various emission clouds in the nebula: red represents nitrogen, green represents hydrogen, and blue represents oxygen.