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NGC 869 and NGC 884 (Double Cluster)


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NGC 869 and NGC 884
Double Cluster (二重星団)
OC I3r

別名 (Other names)
NGC 869 : OCL 350 h Per, Caldwell 14
NGC 884 : OCL 353 Chi Per, Caldwell 14

明るさ (Brightness)

NGC 869 : 5.3等級
NGC 884 : 6.1等級

星座 (Constellation)

ペルセウス座 (Per) (Perseus)

距離 (Distance)
NGC 869 : 6,800光年 (6,800 light-years)

NGC 884 : 7,600光年 (7,600 light-years)

二重星団(にじゅうせいだん、Double cluster )はペルセウス座にある散開星団。
2つの散開星団が接近して存在しているためこの名がある。

カシオペヤ座との境界の近く、天の川のほぼ中央に位置している。 肉眼でも存在が確認できるため、当初単独の恒星と誤認され、西側の星団にはh、東側の星団にはχのバイエル符号が振られた。そのためh+χ(エイチカイ)と呼ばれることがある。 NGCカタログでのカタログ番号は西側の星団がNGC 869、東側の星団がNGC 884。

この天体の存在はすでにヒッパルコスにより記録されている。ただしヒッパルコスはかすかで星はないとしていた。
この天体が星団であることを発見したのは望遠鏡によって観測したガリレオ・ガリレイであるとされている。

ペルセウス座Iアソシエーションの中核をなす星団であり、誕生してから約300万~2,000万年程度経過しているとされている。

NGC 869 and NGC 884 (Double Cluster) is an open cluster located 7,000 light years from the Earth in the constellation Perseus.

NGC 869 and NGC 884 (Double Cluster) : Picture

A Double Star Cluster
A Double Star Cluster
(C) F. Antonucci, M. Angelini, & F. Tagliani, ADARA Astrobrallo
Few star clusters are seen to be so close to each other. Some 7,000 light-years away, though, this pair of open or galactic star clusters is an easy binocular target, a lovely starfield in the northern constellation Perseus. Also visible to the unaided eye from dark sky areas, it was cataloged in 130 BC by Greek astronomer Hipparchus. Now known as h and chi Persei, or NGC 869 (above right) and NGC 884, the clusters themselves are separated by only a few hundred light-years and contain stars much younger and hotter than the Sun. In addition to being physically close together, the clusters' ages based on their individual stars are similar - evidence that both clusters were likely a product of the same star-forming region.

Comet Hartley Passes a Double Star Cluster
Comet Hartley Passes a Double Star Cluster
(C) Ivan Eder
Most star clusters are singularly impressive. Open clusters NGC 869 and NGC 884, however, are doubly impressive. Also known as "h and chi Persei", this unusual double cluster, shown above, is bright enough to be seen from a dark location without even binoculars. Although their discovery surely predates written history, the Greek astronomer Hipparchus notably cataloged the double cluster. The clusters are over 7,000 light years distant toward the constellation of Perseus, but are separated by only hundreds of light years. Captured earlier this month, the bright comet 103P/Hartley, informally called Comet Hartley 2, passed well in front but only a few degrees away from the famous double cluster. Comet Hartley 2, visible on the right, is now fading but still discernable to northern observers with binoculars. No binoculars are needed, of course, if you go right up to the comet's nucleus, as is the plan for NASA's EPOXI spacecraft on November 4.

Double Cluster in Perseus
Double Cluster in Perseus
(C) Volker Wendel, Josef Popsel, Stefan Binnewies
NGC 869 (left) and NGC 884

Star Cluster Dreams
Star Cluster Dreams
(C) Jose Suro

Double Cluster in Perseus
Double Cluster in Perseus
(C) Roth Ritter (Dark Atmospheres)
NGC 869 (above right) and NGC 884

NGC 869 and NGC 884: A Double Open Cluster
NGC 869 & NGC 884: A Double Open Cluster
(C) Thomas V. Davis (tvdavisastropix.com)

Double Cluster (NGC 869 and NGC 884) Double Cluster (NGC 869 and NGC 884)
Double Cluster (NGC 869 and NGC 884)
(C) F. Antonucci, M. Angelini, & F. Tagliani, ADARA Astrobrallo
Double Cluster (NGC 869 and NGC 884)
(C) Volker Wendel, Josef Popsel, Stefan Binnewies
Double Cluster (NGC 869 and NGC 884) Double Cluster (NGC 869 and NGC 884)
Double Cluster (NGC 869 and NGC 884)
(C) Ivan Eder
Double Cluster (NGC 869 and NGC 884)
(C) Jose Suro
Double Cluster (NGC 869 and NGC 884) Double Cluster (NGC 869 and NGC 884)
Double Cluster (NGC 869 and NGC 884)
(C) Roth Ritter
Double Cluster (NGC 869 and NGC 884)
(C) Thomas V. Davis
Double Cluster (NGC 869 and NGC 884) Double Cluster (NGC 869 and NGC 884)
Double Cluster (NGC 869 and NGC 884)
(C) NASA
Double Cluster (NGC 869 and NGC 884)
(C) NASA
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NGC 869 and NGC 884 (Double Cluster) : Movie

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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。
二重星団. (2012, August 13). In Wikipedia.
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