Messier 65: Spiral Galaxy in the Leo Triplet

Messier 65 is the western member of a famous pair of galaxies under the hind leg of Leo. Together with its neighbor M66 and the edge-on galaxy NGC 3628, it makes up the Leo Triplet, one of the best small galaxy groups for a backyard telescope.

What it is

M65 is a spiral galaxy about 35 million light-years away, seen steeply tilted so that it looks like a long, narrow oval. Its visible disk spans about 8 arcminutes, which at that distance works out to roughly 80,000 light-years. It has a bright central bulge, tightly wound arms and a dark dust lane along its nearer edge, and its light comes mostly from old stars.

The three galaxies of the Leo Triplet pull on each other. M66 and NGC 3628 show clear signs of this tug, but M65 looks surprisingly undisturbed. One supernova has been seen in it, in 2013.

When to see it

M65 is a spring object. It is well placed in the evening from March through May and crosses the meridian around 9 p.m. in late April. From 40°N it climbs to about 63° above the southern horizon. Because it lies just north of the celestial equator, it is easy to see from the Southern Hemisphere too, where it sits in the northern sky in autumn.

How to find it

Find the triangle of stars that marks Leo's hindquarters: Denebola at the tail, Zosma (Delta Leonis) on top and Chertan (Theta Leonis) below. Drop from Chertan toward Iota Leonis, a 4th-magnitude star about 5½° to the south-southeast. M65 and M66 sit almost exactly halfway along that line, about 2½° from Chertan. Sweep the spot with a low-power eyepiece; the two galaxies fit in one field, with M65 on the west side.

What you will see

In 10×50 binoculars under a dark sky, M65 and M66 may show as two tiny, faint smudges, but this takes care. A 70–100 mm telescope shows M65 as a small, elongated glow with a brighter middle, oriented roughly north–south. In a 200 mm telescope the oval grows longer, the core stands out, and on a very good night you may sense the dust lane along one side. NGC 3628, about half a degree north, completes the triplet in a wide field. In suburban skies M65 fades badly, and filters do not help.

History

Charles Messier cataloged M65 and M66 on March 1, 1780, describing M65 as a very faint nebula without stars. He noted that he had missed both in November 1773, when a comet he was following passed between them. Some later books credit Pierre Méchain with the discovery, but SEDS traces this to an error. Halton Arp later listed the trio as number 317 in his Atlas of Peculiar Galaxies.