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M25

IC 4725

산개성단 양호 (57/100)
M25 OpenCluster Sagittarius 관측 가능 난이도 3 Medium telescope (6-8") - Wide field preferred
Credit: Starhopper. License: CC BY-SA 4.0. (Wikimedia Commons)
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특성

등급 4.6
각크기 14.1′
거리 2000 ly
Open Cluster [Distance: 2000 ly]

위치 & 식별자

RA 18h 31m 36.0s
Dec -19° 15' 00.0"
별자리 Sagittarius
카탈로그 M25

가시성

사용자 설정에서 관측지를 설정하세요 가시성 데이터를 확인할 수 있습니다.

접안렌즈 시야

108x TFOV: 0.5° Lim. mag: 13.3
N E

M25 · 14.1′ diameter · N up, E left

최적 배율

서베이 이미지

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M25 소개

설명

M25 is a bright open cluster in Sagittarius, about 2,000 light-years from Earth. It contains roughly 600 stars spread across about 19 light-years, with an age of about 90 million years. The cluster includes the notable Cepheid variable star U Sagittarii, one of the few Cepheids in a Messier object.

관측 팁

Located about 6 degrees north of M24. Easily visible in binoculars as a bright, scattered group of stars. A telescope at 40-60x provides the best view, revealing about 30 stars in a loose but attractive pattern. Look for the yellowish Cepheid variable U Sagittarii, which varies from magnitude 6.3 to 7.1 over 6.74 days. Best observed from June through September.

역사

Discovered by Philippe Loys de Cheseaux in 1745-46. Charles Messier cataloged it in 1764. Curiously, M25 was omitted from the NGC catalog due to an error in recording its position, though it later received the IC designation IC 4725.

재미있는 사실

The Cepheid variable U Sagittarii in M25 pulsates with a period of 6.74 days, changing its brightness by nearly a full magnitude. Cepheid variables are crucial 'standard candles' in astronomy — their period-luminosity relationship, discovered by Henrietta Leavitt in 1912, is one of the primary tools for measuring cosmic distances.

커뮤니티 사진 (1)

Credit: Starhopper. License: CC BY-SA 4.0. (Wikimedia Commons)

Credit: Starhopper. License: CC BY-SA 4.0. (Wikimedia Commons)

Skybred Feb 28, 2026