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Hubble · Caldwell 21 · NASA, ESA, A. Aloisi (STScI/ESA), and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration

Caldwell 21

Galaxy in Canes Venatici · 12 million light-years

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TypeGalaxy
ConstellationCanes Venatici
Right ascension12h 28m 11s
Declination+44° 06′
Object distance12 million light-years
Apparent magnitude9.6
Apparent size4.7′ (arc-minutes)
Approx. true diameter16,406 light-years across
Also known asC21 · NGC 4449
Caldwell 21 is a galaxy (NGC 4449) in the constellation Canes Venatici — a distant island of stars far beyond the Milky Way. It appears as number 21 in the Caldwell catalogue, Sir Patrick Moore's 1995 list of 109 bright deep-sky objects for amateur astronomers. It spans roughly 4.7 arc-minutes on the sky. At about magnitude 9.6, it shows up in a small backyard telescope.

Although it appears about 4.7′ wide on the sky, its real span is roughly 16,406 light-years — the difference is a measure of how far away it lies.

Observing Caldwell 21

Caldwell 21 lies in the constellation Canes Venatici and is best placed in the evening sky around March. 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. A small backyard telescope will show it; binoculars may hint at it under dark skies. 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 Caldwell 21 in Universe Finder

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