Night Flight to the Stars
Activity 4A: Mapping a Birth Cloud
The Omega Nebula (M17) is a cloud of gas and dust, which can be seen with binoculars. This object lies just above the "teapot" of
Sagittarius in the general direction of the center of our Galaxy. It's a relatively nearby region of active star formation and is very bright at infrared wavelengths.
The bright stars which light up the visible nebula also warm an invisible cloud of dust to the right of the visible nebula. The warm dust has a temperature of around 100K (-173°C or -279°F) near the stars and drops to 40K (-233°C or -387°F) farther out. Farther out is a very large cloud of cold gas which receives very little radiation.
In M17 hot young stars have formed near the surface of an interstellar cloud. The energy emitted by these stars has created a "blister" on the cloud surface. The bright nebula seen above is a side view of this blister. The dark cloud lies to the right of the visible nebula in this view.