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Messier 101 (The Pinwheel Galaxy)
Hubble · Messier 101 · NASA, ESA, K. Kuntz (JHU), F. Bresolin (University of Hawaii), J. Trauger (Jet Propulsion Lab), J. Mould (NOAO), Y.-H. Chu (University of Illinois, Urbana) and STScI; CFHT Image: Canada-France-Hawaii Telescope/J.-C. Cuillandre/Coelum; NOAO Image: G. Jacoby, B. Bohannan, M. Hanna/NOAO/AURA/NSF

Messier 101

Galaxy in Ursa Major · 21 million light-years

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TypeGalaxy
ConstellationUrsa Major
Right ascension14h 03m 13s
Declination+54° 21′
Object distance21 million light-years
Apparent magnitude7.9
Apparent size24′ (arc-minutes)
Approx. true diameter146,608 light-years across
Also known asM101 · NGC 5457
Messier 101 is a galaxy (also catalogued as NGC 5457) in the constellation Ursa Major — an island of billions of stars far beyond our own Milky Way. It was recorded by Charles Messier in his famous catalogue of 110 deep-sky objects. It spans roughly 24 arc-minutes on the sky. At about magnitude 7.9, it is an easy target for binoculars and small telescopes.

Although it appears about 24′ wide on the sky, its real span is roughly 146,608 light-years — the difference is a measure of how far away it lies.

Observing Messier 101

Messier 101 lies in the constellation Ursa Major and is best placed in the evening sky around April. Its maximum altitude above the horizon depends on your latitude. It is best placed for observers in the northern hemisphere, and sits low for those far south. It is a comfortable target for binoculars and small telescopes. Note that the listed magnitude is spread across the whole object — diffuse galaxies and nebulae are often harder to see than the number alone suggests, so dark, moonless skies help a great deal.

See Messier 101 in Universe Finder

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Sources

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