Messier 96: Spiral Galaxy in Leo

M96 is the brightest member of the Leo I group, a small family of galaxies in the body of Leo. It sits within a degree of M95 and M105, so you can see all three in one short session.

What it is

M96 is a spiral galaxy about 35 million light-years away. Its visible disk spans roughly 60,000 light-years. It looks somewhat lopsided: its arms are uneven, and its core is slightly off center, probably because of gravitational tugs from its neighbors in the group.

The Leo I group, also called the M96 group, includes M95, M105 and several fainter galaxies such as NGC 3384. Radio telescopes have found a huge ring of hydrogen gas around M105 and NGC 3384, a sign of past interactions within the group. In 1998 a Type Ia supernova, SN 1998bu, appeared in M96; this kind of exploding white dwarf is used to measure distances across the universe.

When to see it

From about 40°N, M96 is highest around midnight in early March and around 10 p.m. standard time in early April, reaching about 62° above the southern horizon. Because it lies just north of the celestial equator, it is also visible from most of the Southern Hemisphere, in the northern sky on autumn evenings.

How to find it

Find Regulus, the bright star at the base of the Sickle in Leo, and move about 9° due east. M96 lies about 9.4° east of Regulus at almost the same declination. 52 Leonis, a 5th-magnitude star, is about 2.4° due north of M96 and makes a good signpost. Once you find M96, M95 is about 0.7° to the west, and M105 is about 0.8° to the north-northeast.

What you will see

Under a dark sky, 10×50 binoculars can show M96 as a small, faint smudge; from the suburbs it is difficult. In a 70–100 mm telescope it is an oval glow with a brighter center, clearly brighter than M95, and M105 shows as a small round glow nearby. A 200 mm telescope shows a bright core and an oval halo with an uneven brightness, and the faint galaxy NGC 3384 next to M105. Filters do not help.

History

Pierre Méchain discovered M96 on March 20, 1781, along with M95, and Charles Messier observed both on March 24, 1781. The group they belong to was later recognized as one of the nearest groups of galaxies beyond our Local Group, and the 1998 supernova was studied as a calibrator for cosmic distances.