M17 - The Swan Nebula

Well-positioned for northern and southern observers, the Swan Nebula lies 5,000 light years away among the rich star clouds of Sagittarius about 10 degrees north of the “teapot”. The Swan is one of the three finest emission nebulae visible to small telescopes.

The Basics

• M17 is an emission nebula, which means it's made up of hydrogen gas that emits mostly reddish light upon stimulation from hot young stars that form inside the nebula but are hidden from our sight by obscuring dust.

• Along with the Orion Nebula (M42) and the Lagoon Nebula (M8), the Swan is one of the three finest emission nebula for northern observers with small backyard telescopes. Definitely worth observing over and over again.

A Deeper Look

• The Swan was first observed in the late 1700's, but it's true nature was not determined until William Huggins observed the nebula with a spectroscope and identified the glowing gas as hydrogen.

• Before spectroscopes were turned to the sky, no one was sure if nebula like the Swan were simply unresolved stars, a mysterious shining “fluid”, or something completely unknown. In fact, no one knew what stars were made of, and some respectable scientists declared in the 19th century that humans would never know what celestial objects were made of. Never say never, I suppose!

• In millions more years, the glowing gas of the Swan Nebula will be consumed in star formation, leaving a small open star cluster behind.

Good To Know

Also called the Omega Nebula, the Horseshoe Nebula, and the Checkmark Nebula. Depending on the seeing and levels of light-pollution, you may be able to see all these shapes in M17 as you vary your magnification. The delicate curve of the Swan's “head” is the hardest of all to see: breathe deeply and be patient.

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