NGC 6838 (Globular Cluster, M71)

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NGC 6838, M71
Globular Cluster (球状星団)
Gb X

別名 (Other names)
GCL 115, Messier 71

明るさ (Brightness)

星座 (Constellation)
や座 (Sge) (Sagitta)

距離 (Distance)
13,000光年 (13,000 light-years)

NGC 6838 (M71) is a globular cluster located 13,000 light years from the Earth in the constellation Sagitta.

NGC 6838 (Globular Cluster, M71) : Picture

Messier 71
Messier 71: an unusual globular cluster
(C) NASA/ESA/Hubble
This spectacular NASA/ESA Hubble Space Telescope image shows a bright scattering of stars in the small constellation of Sagitta. This is the centre of the globular cluster Messier 71, a great ball of ancient stars on the edge of our galaxy around 13,000 light-years from Earth. M71 is around 27 light-years across.

Globular clusters are like galactic suburbs, pockets of stars that exist on the edge of major galaxies. These clusters are tightly bound together by their gravitational attraction, hence their spherical shape and their name: globulus means “little sphere” in Latin.

Around 150 such globular clusters are known to exist around our Milky Way, each one of them containing several hundred thousand stars.

Messier 71 has been known for a long time, having been first spotted in the mid eighteenth century by Swiss astronomer Jean-Philippe de Cheseaux. Cheseaux discovered a number of nebulae in his career, and also spent much time studying religion: one posthumously published work attempted to derive the exact date of Christ’s crucifixion from astronomical events noted in the Bible.

Despite being a familiar object, Messier 71’s precise nature was disputed until recently. Was it simply an open cluster, a loosely bound group of stars? This was for many years the dominant view. But in the 1970s, astronomers came to the view that it is in fact a relatively sparse globular cluster.

The stars in Messier 71, as is usual in such clusters, are relatively old, at around 9 to 10 billion years, and consequently are low in elements other than hydrogen and helium.

M71, NGC6838
M71, NGC6838
M71 is a star cluster in the constellation Sagitta. Although more people probably classify it as a globular cluster, despite its rather spread-out appearance, there are still some who maintain it's just a centrally condensed open cluster. The distinction between a loose globular cluster and a condensed open cluster is thus seen to be rather a fine one. At about 12,000 light-years from us, M71 is quite small, probably only 30 or so light-years across, although there are further outlying stars whose membership in M71 is uncertain. This composite was created from images taken in July 1998 at the KPNO 0.9-meter telescope, during the Research Experiences for Undergraduates (REU) program operated at the Kitt Peak National Observatory and supported by the National Science Foundation. Image size 9.1 arc minutes.

Messier 71 M71, NGC6838
Messier 71
M71, NGC6838

NGC 6838 (Globular Cluster, M71) : Movie

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