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He2-104 (Southern Crab Nebula)


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He2-104
Planetary Nebula (惑星状星雲)
Southern Crab Nebula (南のカニ星雲)
Nb PN

別名 (Other names)
Hen2-104

距離 (Distance)
15,000光年 (15,000 light-years)

星座 (Constellation)
ケンタウルス座 (Cen) (Centaurus)

Southern Crab Nebula (He2-104) is a planetary nebula located 15,000 light years from the Earth in the constellation Centaurus.

He2-104 (Southern Crab Nebula) : Picture

He2-104
He2-104
(C) NASA

He2-104
He2-104
(C) NASA
The two stars at the center of this nebula are very different. One is a white dwarf star with a mass similar to our Sun but with a radius as small as our Earth. The other star is a red giant, a star also with mass near our Sun but with a radius so large it could fill the orbit of the Earth. The strange symbiotic relationship between these two stars in the He2-104 system has created a planetary nebula shaped like an hourglass within an hourglass. The red giant star turns out to be a Mira variable, a pulsating star that is dumping mass into an accretion disk surrounding the white dwarf. Astronomers speculate that when enough mass falls onto the white dwarf, a thermonuclear explosion occurs creating another expanding hourglass-shaped nebula. The above photograph was taken with the WFPC2 instrument onboard the Hubble Space Telescope. The hourglasses from the two most recent explosions are visible with the last one highlighted in the inset.

Symbiotic Star Blows Bubbles into Space
Symbiotic Star Blows Bubbles into Space
(C) NASA/ESA
Panel 1: A pulsating red giant star and a compact, hot white dwarf star orbit each other.

Panel 2: The red giant sheds much of its outer layers in a stellar wind. The white dwarf helps concentrate the wind along a thin equatorial plane. The white dwarf accretes some of this escaping gas forming a disk around the itself.

Panel 3: When enough gas accumulates on the white dwarf's surface it explodes as a nova outburst. Most of the hot gas forms a pair of expanding bubbles above and below the equatorial disk.

Panel 4: A few thousand years after the bubbles expand into space, the white dwarf goes through another nova outburst and makes another pair of bubbles, which form a distinctive hourglass shape.

The "Southern Crab" Nebula (He2-104)
The "Southern Crab" Nebula (He2-104)
(C) ESO
The "Southern Crab" Nebula (He2-104). This CCD image of the proto-planetary symbiotic star He2-104, also known as the "Southern Crab", was obtained with the 2.2 metre telescope at La Silla by Hugo Schwarz and collaborators; the exposure time was 30 min. It shows the unusual object in the light of nitrogen ions ([N II] Å). The visual magnitude of the central part is 14.6. The astrophysical interpretation of this image is described in ESO Press Release eso8901 of January 30, 1989.

He2-104 The "Southern Crab" Nebula (He2-104)
He2-104
(C) NASA
The "Southern Crab" Nebula (He2-104)
(C) ESO
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