Anne’s Image of the Day: The Ear Nebula

read more at Anne’s Astronomy News http://annesastronomynews.com/

July 25, 2013

The Ear Nebula, a planetary nebula in Cygnus

Image Credit: T.A. Rector (University of Alaska Anchorage) and H. Schweiker (WIYN and NOAO/AURA/NSF)

The Ear Nebula (designated IPHASX J205013.7 + 465518) is a newly discovered, bipolar planetary nebula of about 6′ long in the northern constellation of Cygnus (the Swan), about 2 degrees northeast of the bright star Deneb.

Despite their name, planetary nebulae have nothing to do with planets. The name of planetary nebulae arose in the 18th century because of the visual similarity between some round planetary nebulae and the planets Uranus and Neptune when viewed through small optical telescopes. 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 star with a mass up to eight times that of the 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 and radiates, producing expanding glowing clouds of gas that can show complex structures, as the ejection of mass from the star is uneven in both time and direction.

Planetary nebulae last for only about 10,000 years, a fleeting episode in the 10-billion-year lifespan of Sun-like stars. So, over the next several thousand years, the Ear 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.

The bright, curved structure in the center of the “ear” has filaments and bipolar outflow. This inner structure is surrounded by a shell, that forms the outer shape of the “ear”. The northern edge is round, the southern edge is less well defined. The direction of motion is toward the upper right (NW) of the Ear Nebula, where the brightest portion of the outer shell is present. The nebula sits in a surrounding background of hydrogen nebulosity.

This relatively old and very faint planetary nebula was discovered by the INT/WFC Photometric H-alpha Survey of the Northern Galactic Plane (IPHAS) in 2012, designed to detect new planetary nebulae interacting with the interstellar medium (ISM) close to the northern galactic plane. But it was apparently first discovered in 2005, and was reported in 2009 by Laurence Sabin et al., “New Candidate Planetary Nebula in the IPHAS Survey; the case of PNe with ISM Interaction“.

This image was obtained with the wide-field view of the Mosaic camera on the Mayall 4-meter telescope at Kitt Peak National Observatory. The image was generated with observations in the Hydrogen alpha (red) and Oxygen [OIII] (blue) filters. In this image, North is up, East is to the left.

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