A new image from NASA's Chandra X-ray Observatory reveals hot gas flowing away from massive young stars in the center of the Horseshoe Nebula, a.k.a. M17 or the Omega Nebula. A group of massive young stars responsible for the activity in the nebula is located in the bright pink region near the center of the image.

Credit: NASA/CXC/PSU/L.Townsley et al.

Chandra's resolving power enabled astronomers to separate the contribution of these and other stars in the nebula from X-rays produced by the hot gas flow, which is shown in red. Temperatures in the hot gas flow range from 1.5 million degrees Celsius (2.7 million degrees Fahrenheit) to about 7 million degrees Celsius (13 million degrees F). The blue color indicates areas where stars are embedded in clouds of dust and gas that absorb low energy X-rays.

An infrared image of the Horseshoe Nebula reveals a cloud of much cooler gas and dust shaped like a horseshoe that gives the nebula its name. The hot gas shown by the Chandra image fits inside the cool gas cloud, and appears to have formed the horseshoe shape by carving a cavity in the cool gas. This activity could lead to the formation of new stars in the Horseshoe.

The stars in the Horseshoe Nebula are only about a million years old, so the nebula is too young for one of its stars to have exploded as a supernova and heated the gas. Collisions between high-speed winds of particles flowing away from the massive stars could heat the gas, or the hot gas could be produced as these winds collide with cool clouds to form bubbles of hot gas. This hot gas appears to be flowing out of the Horseshoe like champagne flows out of a bottle when the cork is removed, so it has been termed an "X-ray champagne flow."

This infrared image of M17 from the 2MASS project penetrates the the dust in this nebular to reveal the otherwise invisible dark molecular cloud. This giant molecular cloud (a cold, dense interstellar cloud which contains a high fraction of molecules) is one of the most luminous and active star-forming regions in the Milky Way. Although the gas in the molecular cloud is too cold to emit visible or near-infrared light, traces of the densest portions of the cloud can still be seen as dark, cloudy strucutres. Credit: 2MASS/UMass/IPAC-Caltech/NASA/NSF

A comparison with other young star clusters confirms that massive young stars are responsible for hot gas clouds like the one seen in the Horseshoe Nebula. The Arches cluster, which contains many massive young stars shows this type of cloud, whereas the central regions of the Orion Nebula, which has few massive young stars, does not.

NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, NASA Headquarters, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.