4.Star Factories in Sagittarius

The golden age of star formation in the Milky Way is long past, but there’s still plenty of activity in dusty spiral arms of the Milky Way. In this astonishing wide-field composite image by astrophotographer +Terry Hancock of Downunder Observatory, for example, you see a half dozen emission nebulae in the Sagittarius Arm of our galaxy in which new stars ignite and set aglow the clouds of gas and dust from which they form.

In this image you see some of the jewels of the Sagittarius Arm. The Eagle Nebula, Messier 16, also known as the “Star Queen” nebula is at the upper right. The open star cluster Messier 25 is at upper left. Between the two is the mottled glow of Messier 17, the Swan Nebula. Each of these nebula lies some 5,000 to 7,000 light years away. At bottom, just left of center, you see the Little Sagittarius Star Cloud, Messier 24, a shimmering patch of stars about 1ºx2º in apparent size and some 9,000 light years away, about 1/3 the way to the center of the galaxy. The annotated image below helps you see which object is which… -

The image above covers about 7º x 4.2º in a region above the “Teapot” of Sagittarius, so it’s roughly what you see in a pair of binoculars (see image below). Of course you see more detail here because light was collected for many hours for each of the four images that make up this composite. Each image was taken with an H-alpha filter, so it favors the reddish-pink light emitted by hydrogen atoms when their electrons recombine after ionization from bright blue-white stars.

Like all emission nebulae, these glowing regions are short-lived blisters of light that only last a few million years. The brightest stars within these regions will eventually push away the remaining gas and dust and leave behind loose clusters of newly minted stars.