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NGC 6254 (Globular Cluster, M10)


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NGC 6254, M10
Globular Cluster (球状星団)
Gb VII


別名 (Other names)
GCL 49, Messier 10

明るさ (Brightness)
6.6等級

星座 (Constellation)
へびつかい座 (Oph) (Ophiuchus)

距離 (Distance)
14,300光年 (14,300 light-years)

M10 (NGC6254) はへびつかい座にある球状星団 。距離14,300光年。1764年シャルル・メシエが発見し「へびつかい座のベルトで見つかった、星を含まない星雲。… 美しく円形をした星雲。単純な3フィートの屈折望遠鏡でかろうじて見ることができる」と記している。初めて星団に分離したのはウィリアム・ハーシェルで、「きれいな星団で、ひどく密集しているM53に似る」としている。直径は約85光年。

密集度の高い、小口径望遠鏡で楽しめる球状星団の一つ。星団内部の星は淡いピンク色をしており、外部のハロー部分は淡い青色をしているとも言われる。また、中心部には黄色な「花火」のような光が見えるという。
周辺部に3つの恒星があり、それが星団をピラミッド状に囲んでいるように見える。

存在そのものは肉眼で確認でき、双眼鏡では容易に確認できる。
M10とM12は、双眼鏡の同じ視野内にぼんやりと星雲状に確認することができる。
球状星団同士のこのような眺めが双眼鏡で楽しめるのは、このM10とM12のペアだけである。
外側の微星は口径10cm程度の望遠鏡から見え始める。口径20cm程度の望遠鏡で少しずつ分離してくる。
しかし、完全に分離するにはさらに大口径の口径30cm程度の望遠鏡でないと難しい。

星団中には変光星は少なく3個しか見つかっていない。
秒速69kmの速度で遠ざかっており、これは銀河系全体の動きから外れていることを意味する。

NGC 6254 (M10) is a globular cluster located 14,300 light years from the Earth in the constellation Ophiuchus.

NGC 6254 (Globular Cluster, M10) : Picture

Globular Cluster M10
Globular Cluster M10
(C) NASA/ESA
Like many of the most famous objects in the sky, globular cluster Messier 10 was of little interest to its discoverer. Charles Messier, the 18th century French astronomer, cataloged over 100 galaxies and clusters, but was primarily interested in comets. Through the telescopes available at the time, comets, nebulae, globular clusters and galaxies appeared just as faint, diffuse blobs and could easily be confused for one another.

Only by carefully observing their motion — or lack of it — were astronomers able to distinguish them: comets move slowly relative to the stars in the background, while other more distant astronomical objects do not move at all.

Messier’s decision to catalog all the objects that he could find, and that were not comets, was a pragmatic solution which would have a huge impact on astronomy. His catalog of just over 100 objects includes many of the most famous objects in the night sky. Messier 10, seen here in an image from the NASA/ESA Hubble Space Telescope, is one of them. Messier described it in the very first edition of his catalog, which was published in 1774 and included the first 45 objects he identified.

Messier 10 is a ball of stars that lies about 15,000 light-years from Earth, in the constellation of Ophiuchus. Approximately 80 light-years across, it should therefore appear about two thirds the size of the moon in the night sky. However, its outer regions are extremely diffuse, and even the comparatively bright core is too dim to see with the naked eye.

Hubble, which has no problems seeing faint objects, has observed the brightest part of the center of the cluster in this image, a region which is about 13 light-years across.

This image is made up of observations made in visible and infrared light using Hubble’s Advanced Camera for Surveys. The observations were carried out as part of a major Hubble survey of globular clusters in the Milky Way.

A version of this image was entered into the Hubble’s Hidden Treasures Image Processing Competition by contestant flashenthunder. Hidden Treasures is an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public. The competition has now closed and the results will be published soon.

Globular Cluster M10
Globular Cluster M10
(C) NASA/ESA
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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。
M10 (天体). (2013, March 23). In Wikipedia.
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