M66
Leo Triplet
Spiral
Properties
Position & Identifiers
Visibility
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About M66
Description
M66 is the largest and brightest member of the Leo Triplet, about 36 million light-years from Earth. It is a spiral galaxy spanning about 95,000 light-years with noticeably asymmetric spiral arms — distorted by gravitational interactions with its neighbors M65 and NGC 3628. The galaxy has hosted four observed supernovae.
Observing Tips
Located just 20 arcminutes east of M65 — the two galaxies share the same low-power field. M66 is slightly brighter and larger than M65. A 4-inch telescope shows an elongated glow. An 8-inch reveals an asymmetric brightness distribution and hints of spiral structure. The three galaxies of the Leo Triplet can be seen together in a wide-field eyepiece. Best observed from March through June.
History
Discovered by Charles Messier on March 1, 1780, together with M65. Four supernovae have been observed in M66: 1973R, 1989B, 1997bs, and 2009hd — making it one of the more prolific supernova hosts.
Fun Facts
M66's spiral arms are clearly asymmetric and displaced from center — pulled out of shape by the gravitational tug-of-war with M65 and NGC 3628. Its high star formation rate and four observed supernovae may be linked to this gravitational interaction, which compresses gas and triggers star formation.
Community Photos (1)
Credit: ESO. License: CC BY 4.0. (Wikimedia Commons)
Skybred Feb 28, 2026