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NGC 4650A (Polar Ring Galaxy)


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NGC 4650A
Polar Ring Galaxy (極リング銀河)
Gx SB0-a

別名 (Other names)
PGC 42891, AM 1241-402, MCG -7-26-38

明るさ (Brightness)
11.8等級

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


距離 (Distance)
1億6,500万光年 (165 million light-years)

極リング銀河(きょくりんぐぎんが)とは、ガスや星々が銀河の中心を回転面に対して垂直に周回する極軌道を持つ銀河。

概要
極リング銀河は、NGC 4650AやNGC 660など、100個以上が発見されている。
極リング銀河は、英語ではpolar-ring galaxyという名称で呼ばれている天体。
なぜこのような天体ができたかについては、まだ結論がでていないが、原因は銀河同士の衝突ではないかと言われている。

NGC 4650A is a polar ring galaxy located 165 million light years from the Earth in the constellation Centaurus.

NGC 4650A (Polar Ring Galaxy) : Picture

Polar Ring Galaxy NGC 4650A
Polar Ring Galaxy NGC 4650A
(C) NASA
NGC 4650A appears to be two galaxies in one. A rare type of galaxy known as a Polar Ring, NGC 4650A is composed of an old central group of stars and a young ring of stars rotating farther out. Both components are clearly visible in this featured photograph by the Hubble Space Telescope. What creates Polar Ring Galaxies is still being researched, but a leading theory is the collision of two distinct galaxies in the distant past. Polar Ring Galaxies allow astronomers to estimate the amount of dark matter in galaxies by measuring the rotation rate of the highly extended ring. An unknown type of dark matter is implied because the ring typically rotates too fast to be held together by only the visible stars.

NGC 4650A: Strange Galaxy and Dark Matter
NGC 4650A: Strange Galaxy and Dark Matter
(C) NASA
This strangely distorted galaxy of stars is cataloged as NGC 4650A. It lies about 165 million light-years away in the southern constellation Centaurus. The complex system seems to have at least two parts, a flattened disk of stars with a dense, bright, central core and a sparse, sharply tilted ring of gas, dust and stars. Observations show that the stars in the disk and the stars and gas in the ring really do move in two different, nearly perpendicular planes, probably as the result of a past galaxy vs. galaxy collision. The observed motions within both disk and ring also indicate the presence of "dark matter" - an unseen source of gravity which influences the movement of this system's visible stars. Over the decades evidence that our Universe is largely composed of such dark matter has grown while the nature of dark matter has remained a profound astrophysical mystery. The picture was constructed from images made using part of the European Southern Observatory's (ESO) new Very Large Telescope system now undergoing its testing phase.
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NGC 4650A (Polar Ring Galaxy) : Movie

MUSE — Running through the 3D data of NGC 4650A
This view shows how the new MUSE instrument on ESO's Very Large Telescope gives a three-dimensional view of a distant galaxy. For each part of the galaxy the light has been split up into its component colours — revealing not only the motions of different parts of the galaxy but also clues to its chemical composition and other properties. At certain wavelengths the emission from the rotating disc around the galaxy is clearly seens, as well as the different velocities of different parts of the disc.

MUSE views the unusual galaxy NGC 4650A
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「ウィキペディア(wikipedia):フリー百科事典」より文章引用。
極リング銀河. (2012, October 3). In Wikipedia.
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