Messier 16: The Eagle Nebula

Messier 16 is the Eagle Nebula, a cloud of glowing hydrogen around a young cluster of hot stars in the tail of Serpens. Its central dark columns, the Pillars of Creation, became famous through the Hubble Space Telescope. At the eyepiece it is subtler than the photos.

What it is

M16 has two parts. The catalog entry NGC 6611 is an open cluster of young, hot stars, about 5,540 light-years away according to Gaia measurements. Around it lies a large emission nebula (catalogued separately as IC 4703), a cloud of gas and dust in which stars are still forming. Ultraviolet light from the cluster's hottest stars makes the hydrogen glow red in photographs, and the same light slowly erodes the cloud. The Pillars of Creation are dense columns of cold gas and dust that resist this erosion; new stars are forming inside their tips. M16 lies in the same spiral arm of the Milky Way as its neighbor the Omega Nebula, M17, about 2.5° to the south.

When to see it

M16 is a summer object. From about 40°N it is highest in the south around 11 p.m. daylight time in late July, and it stays well placed in the evening through August and early September. It reaches about 36° above the horizon at 40°N, so it sits in the thick of the summer Milky Way above Sagittarius. From the Southern Hemisphere it passes high overhead and is excellent.

How to find it

Start from the small, compact constellation Scutum and its brightest star in this area, Gamma Scuti (magnitude 4.7). M16 lies about 2.6° west and slightly north of Gamma Scuti. If you already know the Omega Nebula, M17, which is brighter and easier to spot, simply move about 2.5° north of it to reach M16. Both fit in a single binocular field.

What you will see

In binoculars M16 shows as a small group of stars inside a faint haze, best from a dark site. A 70–100 mm telescope at low power shows a scattered cluster of a few dozen stars with a soft glow around them; the nebula is easy to miss from suburban skies. A 200 mm or larger telescope under dark skies shows the nebula as an irregular glow with darker bays, and experienced observers can pick out the Pillars as dark notches against the light. A UHC or O-III filter improves the contrast of the nebula a great deal; the cluster stars dim, but the gas stands out.

History

The Swiss astronomer Philippe Loys de Chéseaux discovered the star cluster in 1745. Charles Messier observed it in 1764 and was the first to note the faint glow around the stars. In 1995 the Hubble Space Telescope imaged the Pillars of Creation, and the picture became one of the best-known astronomical images ever made. Hubble returned in 2014, and the James Webb Space Telescope imaged the Pillars in infrared in 2022.