Messier 97: Owl Nebula

The Owl Nebula sits just under the bowl of the Big Dipper, close to the galaxy M108. It is one of the fainter Messier objects, a dim round disk that rewards a dark sky, a filter and patience. Under the right conditions you may glimpse the two darker "eyes" that give it its name.

What it is

M97 is a planetary nebula: the outer layers of a dying Sun-like star, blown off and lit up by the hot core left behind. That core is now a small, very hot star on its way to becoming a white dwarf. The nebula lies about 2,660 light-years away, a distance based on Gaia measurements of the central star, and at that range its 3.4′ disk is roughly 2½ light-years across. The two dark patches are thought to be the ends of a hollow, barrel-shaped inner shell seen at an angle.

When to see it

M97 is a spring object, highest around midnight in early March and well placed in the evening through April and May. From about 40°N it climbs to roughly 75° and never sets, so you can find it on any clear night, though it is low in the north on autumn evenings. From the Southern Hemisphere it barely clears the northern horizon from around 30°S and is out of reach farther south.

How to find it

Start at Merak, the star at the bottom corner of the Dipper's bowl on the handle-less side. M97 lies about 2.3° southeast of Merak, roughly a quarter of the way toward Phecda, the other bottom corner of the bowl. On the way you pass M108, about 1.5° from Merak; the Owl is a further 0.8° to the southeast. A wide-field eyepiece can hold both objects at once.

What you will see

In binoculars M97 is very hard: under a dark sky, 10×50s may show a tiny, faint, round haze. A 70–100 mm telescope shows a pale gray disk with no detail, about four times the apparent width of Jupiter; from suburban skies it can vanish entirely. A 200 mm or larger telescope shows a soft, evenly lit disk, and with averted vision and an O-III or UHC filter the two darker eyes begin to appear. The filter helps more here than almost anywhere else in the Messier list.

History

Pierre Méchain found the nebula on February 16, 1781, and Messier measured its position the following month. Messier noted it was hard to see, especially when the field was lit. The name came from William Parsons, the third Earl of Rosse, whose 1848 drawing through his large reflector showed two dark holes that looked like an owl's eyes.