Anne’s Picture of the Day: Planetary Nebula NGC 5189

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April 5, 2013

NGC 5189, a planetary nebula in Musca

Image Credit & Copyright: Robert Gendler (http://www.robgendlerastropics.com)

NGC 5189 (also known IC 4274 and the Spiral Planetary Nebula) is a symmetric planetary nebula of about 3 light-years across, located some 3,000 light-years away from Earth in the southern constellation of Musca, the Fly. It is slowly approaching us at approximately 9.5 kilometers per second.

Despite their name, planetary nebulae have nothing to do with planets. The name of planetary nebulae arose because of the visual similarity between some round planetary nebulae and the planets Uranus and Neptune when viewed through early telescopes.

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 and radiates, producing glowing clouds of gas that can show complex structures, as the ejection of mass from the star is uneven in both time and direction.

NGC 5189 certainly does not mimic a planet: the nebula forms a distinctive S-shape. The overall shape can tell us about what is happening on very small scales around the tiny central star (HD 117622). It is reminiscent of a lawn sprinkler, with matter being expelled from the star, which is wobbling as it rotates.

Most of the nebula is filamentary in its structure with a series of dense knots in the clouds of gas. These knots are a reminder of just how vast the nebula is. They might look like mere details in this image, but each and every one is a similar size to the entire Solar System.

The gas and radiation flowing out from the dying central star carves out shapes in the clouds, forming glowing bow-wave-like patterns towards the center of the nebula. This star, a dense white dwarf, is far too small to see as anything other than a point of light, even though it is roughly the size of the Earth.

The double bipolar structure of NGC 5189 could be explained by the presence of a binary companion orbiting the central star and influencing the pattern of mass ejection during its nebula-producing death throes. However, there is no visual candidate for the possible companion.

This composite image is based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive.

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