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March 19, 2013

Jones-Emberson 1, a planetary nebula in Lynx

PK 164+31.1, the Headphone Nebula

Image Credit & Copyright: J-P Metsävainio (http://astroanarchy.zenfolio.com)

Jones-Emberson 1 (PK 164+31.1) is a faint planetary nebula of about 4 light-years across that lies about 1,600 light-years away from Earth in the northern constellation of Lynx, while it is approaching us at approximately 84.3 kilometers per second. For obvious reasons it is sometimes nicknamed the Headphone Nebula.

The name is derived from R. Jones and R. Emberson, who discovered the nebula in 1939; it’s “PK” designation comes from the names of Czechoslovakian astronomers Luboš Perek and Luboš Kohoutek, who in 1967 created an extensive catalog of all of the planetary nebulae known in the Milky Way as of 1964. The numbers indicate the position of the object on the sky. (“PK 164+31.1″ has a galactic longitude of 164 degrees, a galactic latitude of +31 degrees, and is the first such object in the Perek-Kohoutek catalog to occupy that particular one square degree area of sky).

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. They are called “planetary” nebulae because early observers thought they looked like planets; but they don’t have anything to do with planets at all.

This larger planetary nebula is composed of stellar gasses expelled from the tiny central star, a very blue white dwarf. It has a low surface brightness with two brighter lobes. However, the intense ultraviolet light emitted by this star makes elements in a ring glow. The outer red shell consists mainly of ionized hydrogen, whereas the inner blue area comprises mainly ionized oxygen.

The gas in all nebulae is extremely thin. Even in the densest parts, the vacuum is still much better than can be created in laboratories on Earth. It is only because these objects occupy so much space that we can see them at all. In the case of Jones-Emberson 1, the inner gasses are thin enough to allow galaxies and stars behind it to be easily seen.

Over the next several thousand years, Jones-Emberson 1 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.

Due to its faintness and low surface brightness, this nebula is only visible with a good-sized telescope.

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