Messier 74: Face-On Spiral Galaxy in Pisces

Messier 74 is a textbook spiral galaxy seen almost perfectly face-on, a pinwheel of arms around a small bright core. In photographs it is beautiful. At the eyepiece it is one of the hardest Messier objects, because its light is spread so thinly.

What it is

M74 is a spiral galaxy about 32 million light-years away. Its disk covers about 10 arcminutes, which at that distance is roughly 95,000 light-years across, about the size of our own Milky Way. It is a "grand-design" spiral: two well-defined arms wind out from the center, lined with clusters of young blue stars and pink clouds of glowing hydrogen where stars are forming. It has no central bar.

Three supernovae have been discovered in M74 since 2002: SN 2002ap, SN 2003gd and SN 2013ej. SEDS notes that the first was an unusually powerful explosion of a very massive star.

When to see it

M74 is an autumn object. It is highest in the south around midnight in late October and around 10 p.m. in late November. From 40°N it climbs to about 66°. Lying just north of the celestial equator, it is visible from the Southern Hemisphere too, low in the north on spring evenings there.

How to find it

Start at Hamal, the brightest star of Aries, and follow the line through Sheratan (Beta Arietis) and on to Eta Piscium, a 3.6-magnitude star about 8° southwest of Sheratan. From Eta Piscium, move about 1⅓° east-northeast. A pair of 6th-magnitude stars, 103 and 105 Piscium, lies about a degree northeast of the galaxy and helps confirm the field.

What you will see

This is a galaxy where sky darkness matters more than anything. Under a truly dark sky, binoculars may show a very faint round glow. A 70–100 mm telescope usually shows only the small, almost star-like core with a hint of haze around it; the core is compact enough to pass for a star. In a 200 mm telescope on a dark night the round glow around the core grows to perhaps 6 to 8 arcminutes, and with averted vision you may sense a mottled texture or a hint of the arms. Under suburban skies it can vanish entirely. Use low to medium power, since high power spreads the faint light even thinner. No filter helps.

History

Pierre Méchain discovered M74 at the end of September 1780 and told Charles Messier, who measured its position and added it to his catalog on October 18, 1780. Lord Rosse listed it among the 14 spiral nebulae found before 1850, making it one of the first galaxies whose spiral shape was recognized. In 1860 Friedrich Argelander's Bonner Durchmusterung survey cataloged its nearly star-like core as a star.