Picture of the Week

Hubble camera's farewell postcard

    This planetary nebula, called Kohoutek 4-55 (or K 4-55 for short), was released as the Hubble Wide Field Planetary Camera 2's last image before it was upgraded last month, after 16 years of operation.

     Confusingly, planetary nebulae aren't anything to do with planets, but are in fact the outer layers of a dead red giant star that are thrown off when the star reaches the end of its life. Radiation from the core of the star lights up the shells of gas that were thrown off, to make spectacular patterns like those seen in K 4-55. The different colours represent different types of gas: red represents nitrogen, green hydrogen and blue oxygen.

Image: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).