Messier 96, NGC 3368

Messier 96 (NGC 3368) is a conspicuous spiral galaxy in Leo, and forms a pair with M 95 near the middle of the constellation. M 96 is the eastern member of this fine 40'-wide pair.

M 96 was discovered, along with M 95, by Pierre Mechain in 1781, and catalogued by Charles Messier that same year. It was among the first 14 "spiral nebulae" listed by Lord Rosse in 1850.

M 95, 96, 65, and 66 are all members of the same Leo I group of galaxies. M 96 appears to be the brightest, with a visual magnitude of 9.2. It is a bright oval, 6' x 4' across, containing a brilliant core with a non-stellar nucleus. Its periphery is irregular both in brightness and in shape, and bulges toward the southeast. It has a prominent dust lane which extends through the nucleus.

One bright supernova, SN 1998bu, has been observed in M 96.

The bright inner disk of M 96 is composed of an older, yellow stellar population, which ends slightly beyond a ring of blue knots. These knots are probably clusters of hot, young stars. This galaxy contains a significant amount of dust, which appears more concentrated on its near side. M 96 is inclined by 35° to our line of sight, and rotates with its spiral arms trailing.

M 96 is about 41 million light years away, as determined by Hubble Space Telescope observations of Cepheid variables within it. At this distance, its apparent diameter corresponds to a linear dimension of 66,000 light years. However, this galaxy has an outer ring of filaments extending out to a diameter of at least 100,000 light years. Its apparent brightness corresponds to an absolute magnitude of -21.1, or a luminosity of 24 billion Suns.