Planetary nebula K 4-55

The Hubble community bids farewell to the soon-to-be decommissioned Wide Field Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope. In tribute to Hubble's longest running optical camera, a planetary nebula has been imaged as WFPC2's final "pretty picture".

This planetary nebula is known as Kohoutek 4-55 (or K 4-55). It is one of a series of planetary nebulae that were named after their discoverer, Czech astronomer Luboš Kohoutek. A planetary nebula is formed from material in the outer layers of a red giant star that were expelled into interstellar space when the star was in the late stages of its life. Ultraviolet radiation emitted from the remaining hot core of the star ionises the ejected gas shells, causing them to glow.

In the specific case of K 4-55, a bright inner ring is surrounded an asymmetric, fainter layer. The entire system is then surrounded by a faint red halo of light emitted by ionised nitrogen. This multi-shell structure is fairly uncommon in planetary nebulae.