Messier 94: Spiral Galaxy in Canes Venatici

M94 is one of the brightest spring galaxies and one of the easiest to find, sitting in a triangle with the two main stars of Canes Venatici. Its very bright center makes it stand out even in small telescopes and under suburban skies.

What it is

M94 is a spiral galaxy about 16 million light-years away, much closer than the galaxies of the Virgo Cluster. Its bright inner disk spans roughly 30,000 light-years, and a much fainter outer disk or ring reaches farther out.

Its most notable feature is a bright ring of new star formation surrounding its core, where gas has piled up and is turning into clusters of young, hot stars. Inside the ring, the nucleus itself is unusually bright and compact. M94 is part of a loose group of galaxies in Canes Venatici; the bright spirals M63 and M51 lie in the same general region of sky.

When to see it

From about 40°N, M94 is highest around midnight in mid-April and around 10 p.m. standard time (11 p.m. daylight time) in mid-May, when it passes almost straight overhead, about 89° up. It is circumpolar from latitudes north of about 49°, such as most of Canada and northern Europe, so it never sets there. From the Southern Hemisphere it stays low in the north and is out of reach south of about 49°S.

How to find it

Find Cor Caroli (Alpha Canum Venaticorum), the 3rd-magnitude star below the handle of the Big Dipper, and Chara (Beta Canum Venaticorum), a fainter 4th-magnitude star about 5° to its northwest. M94 forms a triangle with them: it lies about 3° east of Chara and about 3° north-northwest of Cor Caroli. Aim your finder there and look for a small, star-like glow.

What you will see

In 10×50 binoculars M94 shows as a small, bright smudge, almost like a fuzzy star; it is visible from the suburbs on a clear night. A 70–100 mm telescope shows an oval glow with a very bright, concentrated center. A 200 mm telescope reveals a small, intense core surrounded by a brighter inner zone, which is the star-forming ring, then a fainter oval halo. The faint outer ring needs a large telescope and a dark sky. Filters do not help.

History

Pierre Méchain discovered M94 on March 22, 1781, and Charles Messier observed it two days later and added it to his catalog, describing it as a nebula with a shining center. Later studies revealed the ring of star formation around its core and the faint outer ring that make it look so different from most spirals in a telescope.