Book contents
- Frontmatter
- Dedication
- Contents
- Foreword
- Preface
- User Guide
- Charles Messier
- The Observations
- The Catalog
- Statistics of the Messier objects
- Visual observation of the Messier objects
- Photography of the Messier objects
- The 110 Messier objects
- M 1
- M 2
- M 3
- M 4
- M 5
- M 6
- M 7
- M 8
- M 9
- M 10
- M 11
- M 12
- M 13
- M 14
- M 15
- M 16
- M 17
- M 18
- M 19
- M 20
- M 21
- M 22
- M 23
- M 24
- M 25
- M 26
- M 27
- M 28
- M 29
- M 30
- M 31
- M 32
- M 33
- M 34
- M 35
- M 36
- M 37
- M 38
- 39
- M 40
- M 41
- M 42
- M 43
- M 44
- M 45
- M 46
- M 47
- M 48
- M 49
- M 50
- M 51
- M 52
- M 53
- M 54
- M 55
- M 56
- M 57
- M 58
- M 59
- M 60
- M 61
- M 62
- M 63
- M 64
- M 65
- M 66
- M 67
- M 68
- M 69
- M 70
- M 71
- M 72
- M 73
- M 74
- M 75
- M 76
- M 77
- M 78
- M 79
- M 80
- M 81
- M 82
- M 83
- M 84
- M 85
- M 86
- M 87
- M 88
- M 89
- M 90
- M 91
- M 92
- M 93
- M 94
- M 95
- M 96
- M 97
- M 98
- M 99
- M 100
- M 101
- M 102
- M 103
- M 104
- M 105
- M 106
- M 107
- M 108
- M 109
- M 110
- Glossary of technical terms
- Index of figures
- Index of sources
M 13
from The 110 Messier objects
Published online by Cambridge University Press: 05 August 2015
- Frontmatter
- Dedication
- Contents
- Foreword
- Preface
- User Guide
- Charles Messier
- The Observations
- The Catalog
- Statistics of the Messier objects
- Visual observation of the Messier objects
- Photography of the Messier objects
- The 110 Messier objects
- M 1
- M 2
- M 3
- M 4
- M 5
- M 6
- M 7
- M 8
- M 9
- M 10
- M 11
- M 12
- M 13
- M 14
- M 15
- M 16
- M 17
- M 18
- M 19
- M 20
- M 21
- M 22
- M 23
- M 24
- M 25
- M 26
- M 27
- M 28
- M 29
- M 30
- M 31
- M 32
- M 33
- M 34
- M 35
- M 36
- M 37
- M 38
- 39
- M 40
- M 41
- M 42
- M 43
- M 44
- M 45
- M 46
- M 47
- M 48
- M 49
- M 50
- M 51
- M 52
- M 53
- M 54
- M 55
- M 56
- M 57
- M 58
- M 59
- M 60
- M 61
- M 62
- M 63
- M 64
- M 65
- M 66
- M 67
- M 68
- M 69
- M 70
- M 71
- M 72
- M 73
- M 74
- M 75
- M 76
- M 77
- M 78
- M 79
- M 80
- M 81
- M 82
- M 83
- M 84
- M 85
- M 86
- M 87
- M 88
- M 89
- M 90
- M 91
- M 92
- M 93
- M 94
- M 95
- M 96
- M 97
- M 98
- M 99
- M 100
- M 101
- M 102
- M 103
- M 104
- M 105
- M 106
- M 107
- M 108
- M 109
- M 110
- Glossary of technical terms
- Index of figures
- Index of sources
Summary
The Great Hercules Cluster
Degree of difficulty 1 (of 5)
Minimum aperture Naked eye
Designation NGC 6205
Type Globular cluster
Class V
Distance 25,890 ly (R2005) 24,530 ly (CMD, 1998)
Size 160 ly
Constellation Hercules
R.A. 16h 41.7min
Decl. +36° 28′
Magnitude 5.7
Surface brightness –
Apparent diameter 21′
Discoverer Halley, 1714
History In 1714, Edmond Halley noticed, more or less by accident, a “nebulous patch” in the constellation of Hercules. A year later, he wrote up a list of the six nebulae then known to him (M 42, M 31, M 22, ω Cen, M 11, and M 13) and commented about the latter: “This is but a little patch, but it shows itself to the naked eye, when the sky is serene and the moon absent.” Charles Messier observed M 13 on the 1st of June 1764, and noted: “Nebula without star, discovered in the girdle of Hercules; it is round & brilliant, the center brighter than the borders; it is near two stars, both of 8th magnitude, one of them above & the other below; 6′ diameter.”
It was left to William Herschel to recognize the true nature of this star cluster in 1784: “A most beautiful cluster of stars. It is exceedingly compressed in the middle and very rich. About 14,000 stars can be counted.” 40 years later, John Herschel commented: “Very rich cluster; irregular figure; very large; very gradually much brighter toward the middle; stars from 10th to 15th magnitude, of which there must be thousands; does not come up to a nucleus; has hairy-looking curvilinear branches.” This impression was shared by Lord Rosse, who pointed his large 72-inch mirror towards M 13: “singularly fringed appendages to the globular figure out into the surrounding space.” His drawing shows a Y-shaped dark structure over the whole central region of the cluster. D'Arrest, too, saw “arm-shaped outliers” with a magnification of 95×.
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- Information
- Atlas of the Messier ObjectsHighlights of the Deep Sky, pp. 100 - 103Publisher: Cambridge University PressPrint publication year: 2008
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