NGC 6210, a planetary nebula in Hercules

NGC 6210, a planetary nebula in Hercules

NGC 6210 is small but fairly bright planetary nebula, located about 6,500 light-years away in the constellation of Hercules. The entire nebula measures 1.6 light-years while the inner shell is about 0.5 light-years in diameter. The nebula is moving away from us at 14 kilometers per second. The colors in this image are caused by ionized oxygen.

Planetary nebulae have nothing to do with planets, the term for this class of objects originated because when viewed through a small telescope in the 16th century, these objects appeared to be clouds (nebulae) that were similar in appearance to Uranus, which was just discovered. The name has not been changed, even though planetary nebulae are now known to be completely unrelated to the planets of the Solar System.

NGC 6210 is the last gasp of a star slightly less massive than our Sun at the final stage of its life cycle. The multiple shells of material ejected by the dying star form a superposition of structures with different degrees of symmetry, giving NGC 6210 its odd shape.

The life of a star ends when the fuel available to its thermonuclear engine runs out. The estimated lifetime for a Sun-like star is some ten billion years. When the star is about to expire, it becomes unstable and ejects its outer layers, forming a planetary nebula and leaving behind a tiny, but very hot, remnant, known as white dwarf. This compact object, here visible at the centre of the image, cools down and fades very slowly. Stellar evolution theory predicts that our Sun will experience the same fate as NGC 6210 in about five billion years.

This sharp image shows the inner region of this planetary nebula in unprecedented detail, where the central star is surrounded by a thin, bluish bubble that reveals a delicate filamentary structure. This bubble is superposed onto an asymmetric, reddish gas formation where holes, filaments and pillars are clearly visible.

At least two bipolar jets of material flung off by the central star can be seen in the image. The jets are thought to be driven by a “fast wind” – material propelled by radiation from the hot central star. Research suggests that the jets occur episodically and also that the various shells are not of the same age. The central star likely ejected its outer layers in several periods, reshaping the nebula created by the fast stellar winds several times.

This picture was created from images taken with Hubble’s Wide Field Planetary Camera 2.
Image Credit: ESA/Hubble and NASA

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