Messier 74 (NGC 628) is a spiral galaxy out of the top-drawer. This far-flung island universe yields awe-inspiring images, its sweeping spiral arms being presented in the ‘grand-design’ manner. This term is reserved for face-on spirals characterised by prominent spiral arms that wrap around the nucleus in a fashion similar to the magnificent Whirlpool Galaxy (Messier 51), probably the archetypal grand-design spiral.
Messier 74’s has two, well-defined spiral arms that are less chaotic than those of say Messier 101, another member of the grand design club, and a small yet bright nucleus. Messier 74 appears almost totally face-on to our perspective, it being tilted away from us by just five degrees. This helps astronomers to easily study Messier 74’s spiral arms. We have a front-row seat to trace dust lanes seen primarily in their inner region and young, hot blue star clusters and glowing pink, diffuse HII regions, sites of further star formation, seen dotted along their entire length.
How to observe
Messier 74 (NGC 628) is located in the far eastern reaches of Pisces, the constellation whose western end, including its ‘Circlet’ asterism, lies to the south of the Great Square of Pegasus. M74 is located north of Pisces’ main line of stars which stretch from the Circlet to magnitude +3.8 Alrescha (alpha [α] Piscium) in its far south-east. It lies nearly 15 degrees north-west of Alrescha, but it may be easier to find by sweeping for it 10 degrees south-west of brighter Hamal (alpha Arietis, magnitude +2).
At mid-month, M74 culminates (is highest in the local southern sky) at a favourable altitude of around 55 degrees at about 1am BST from southern England. It achieves a reasonable altitude of above 30 degrees in the east-southeast between 9pm and 5am BST.
Messier 74 is a large galaxy which appears face-on to our line of sight. It covers 11 <M>x<M> 11 arcminutes across, about a third of the size of the full Moon, and has a catalogued magnitude of +9.2. Essentially, this means the equivalent of the concentrated light of a magnitude +9.2 star is spread out over its entire face-on form, which unfortunately gives M74 a low surface brightness.
Low surface brightness
While deep-sky imagers of Messier 74 enjoy carte blanche, it’s often a far different story for visual observers confronting the galaxy. All face-on spiral galaxies are blighted by low surface brightness to some degree, including the likes of the Whirlpool Galaxy, though Messier 74 has the unenviable reputation as perhaps the toughest visual target in the Messier catalogue. However, a pair of binoculars or a finderscope can reveal it as a fuzzy oval of light on a fine, moonless night at an observing site free from major light pollution. Use low powers when sweeping for M74 through a small telescope; an 80mm (~three-inch) refractor can show a circular patch about five arcminutes across.
Upgrading to a 200mm- (eight-inch-) aperture telescope and ramping up the magnification reveals some mottling, this being the unresolved and faint traces of M74’s graceful and well-ordered spiral arms surrounding its small core. Present-day deep-sky images, preferably shot through long-focus telescopes, are breathtaking, displaying the galaxy at its photogenic best.