MWP1, an ancient planetary nebula in Cygnus

MWP1, an ancient planetary nebula in Cygnus

Image Credit & Copyright: Don Goldman, Astrodon Imaging (

MWP1 (named after its discoverers C. Motch, K. Werner and M. Pakull) is a 150,000 years old, faint bipolar planetary nebula of about 15 light-years across, located some 4,500 light-years away in the northern constellation of Cygnus (the Swan). It is expanding with a velocity of approximately 20 kilometers per second.

Despite their name, planetary nebulae have nothing to do with planets. The name was coined by Sir William Herschel because when he first viewed a planetary nebula through a telescope, he could only identify a hazy smoky sphere, similar to gaseous planets such as Uranus. The name has stuck even though modern telescopes make it obvious that these objects are not planets at all.

Planetary nebulae represent the final brief stage in the life of a medium-sized star like our Sun. While consuming the last of the fuel in its core, the dying star expels a large portion of its outer envelope. This material then becomes heated by the radiation from the stellar remnant (collapsing from a red giant to a white dwarf) and radiates, producing outward-moving glowing clouds of gas.

Over the next several thousand years, the nebula will gradually disperse into space, and then the white dwarf will cool and fade away for billions of years. Our own Sun is expected to undergo a similar fate, but fortunately this will not occur until some 5 billion years from now.

MWP1 is one of the oldest planetary nebulae known, and is therefore sometimes nicknamed the Methuselah Nebula. It is also one of the largest planetary nebulae known, and its progenitor star is one of the hottest stars known, so hot it is producing large amounts of X-rays. The bipolar structure of MWP1 may suggest that the central star is a close binary system or one that has a significant magnetic field.

Because planetary nebulae ordinarily only last for 10 to 20 thousand years, the truly ancient MWP1 offers a challenge to astronomers for studying the evolution of the nebula and its central white dwarf star with the prosaic name RX J2117.1+3412.

This image is taken on October 11, 2010 with the Apogee U16M Camera on the RCOS 16 Telescope, located at the Sierra-Remote Observatories, Shaver Lake, California, USA. North is up, East is to the left.

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