Astronomy Picture of the Day

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2000 September 6 Emerging Planetary Nebula CRL 618 Credit: Susan R. Trammell (UNC Charlotte) et al., ESAIC, HST, ESA, NASA

Explanation: CRL 618 may look to some like an Olympian declaring victory. Only a few hundred years ago, however, CRL 618 appeared as a relatively modest red giant star. Since then it has run out of core material to fuse and so has started to become a planetary nebula. In its current proto-planetary nebula phase, CRL 618 is evolving quickly, expelling hot gasses in complex jets and rings moving outwards faster than 700,000 kilometres per hour. In a few thousand years, the glowing core of the cool red giant will be bare, revealing a hot white dwarf star. Much remains unknown about planetary nebulae formation, including details of how geometries like this form. Perhaps one day some part of this nebula will be able to declare victory - CRL 618 has an extraordinary abundance of carbon-chain molecules.