M71
Angelfish Cluster
천체 데이터
- 카탈로그 지정명
- M71
- 유형
- GlobularCluster
- 별자리
- Sagitta
- 등급
- 8.2
- 적경
- 19h 53m 46.5s
- 적위
- +18° 46' 45.1"
- 거리
- 13,000 광년
- 각크기
- 7.2
서베이 이미지
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M71 소개
설명
M71 is an unusual cluster in Sagitta, about 12,000 light-years from Earth. Long debated as either a dense open cluster or a loose globular cluster, it is now classified as a globular — one of the loosest and most metal-rich known. It spans about 27 light-years and contains several thousand stars, far fewer than typical globulars.
관측 팁
Located in the middle of the small constellation Sagitta (the Arrow), roughly midway between Gamma and Delta Sagittae. In binoculars it appears as a faint, irregular hazy patch. A 4-inch telescope at 60-80x shows a loose, mottled glow that looks more like a dense open cluster than a globular. Individual stars are resolved even in small telescopes due to its loose structure. Best observed from July through October.
역사
Discovered by Philippe Loys de Cheseaux in 1745-46 and independently found by Johann Gottfried Koehler around 1775. Charles Messier cataloged it on October 4, 1780. Its classification was debated for over two centuries before modern studies confirmed it as a globular cluster.
재미있는 사실
M71 blurs the line between globular and open clusters. At about 9 billion years old, it is much younger than typical globulars (which are usually 12-13 billion years). Its high metallicity and loose structure once led many astronomers to classify it as an open cluster, making it a fascinating case study in stellar classification.
커뮤니티 사진 (1)
Credit: ESA/Hubble and NASA. License: CC BY 3.0. (Wikimedia Commons)
Skybred Feb 28, 2026