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NGC 5979 (Planetary Nebula)


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NGC 5979
Planetary Nebula (惑星状星雲)
Nb PN


別名 (Other names)
PK 322-5.1, ESO 136-PN3

明るさ (Brightness)
11.5等級

星座 (Constellation)
みなみのさんかく座 (TrA) (Triangulum Australe)

距離 (Distance)
11,700光年 (11,700 light-years)

NGC 5979 is a planetary nebula located 11,700 light years from the Earth in the constellation Triangulum Australe.

NGC 5979 (Planetary Nebula) : Picture

NGC 5979 (Planetary Nebula)
NGC 5979 (Planetary Nebula)
(C) ESA, ESO and NASA
NGC 5979 is a planetary nebula of a little over ⅔ of a light-year across, located some 11,700 light-years away from Earth in the southern constellation of Triangulum Australe, while it is moving away from us at only about 23 kilometers per second.

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, but the glowing gassy outer layers thrown off by a hot dying star.

A medium-sized star like our Sun spends most of its life quietly converting hydrogen into helium. However when the hydrogen in the stellar core is exhausted, 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.

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, NGC 5979 will gradually disperse into space, and then the white dwarf, HD 140586, 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.

This previously unreleased colour image of the planetary nebula NGC 5979 is a composite of raw FITS files made with the ESA/ESO/NASA Photoshop FITS Liberator. The image was composed from four individual exposures taken through: A blue narrow-band filter (502 nm, 460 seconds showing the forbidden OIII line), A green wide-band filter (555 nm, 240 seconds), An orange-red narrow-band filter (658 nm, 1200 seconds showing the forbidden NII line), A red, or near-infrared, wide-band filter (814 nm, 480 seconds).

Stars like the Sun spend most of their life quietly converting hydrogen into helium. However when the hydrogen in the stellar core is exhausted, they start a short phase of much more rapid evolution, growing in size and brightness, to become cooler red giants that begin to eject large amounts of gas and dust as a slow stellar wind.

When the star has lost most of its mass, it heats up again and brightens so that the ejected material begins to glow. At the same time a faster wind sweeps through to clear out the cocoon of obscuring material and so a planetary nebula is born.

NGC 5979 (Planetary Nebula)
NGC 5979 (Planetary Nebula)
(C) ESA, ESO and NASA
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