A Tour of W51

In the context of space, the term 'cloud' can mean something rather different from the fluffy white collections of water in the sky or a way to store data or process information. Giant molecular clouds are vast cosmic objects, composed primarily of hydrogen molecules and helium atoms, where new stars and planets are born. These clouds can contain more mass than a million suns, and stretch across hundreds of light years.

The giant molecular cloud known as W51 is one of the closest to Earth at a distance of about 17,000 light years. Because of its relative proximity, W51 provides astronomers with an excellent opportunity to study how stars are forming in our Milky Way galaxy.

A new composite image of W51 shows the high-energy output from this stellar nursery. In about 20 hours of Chandra exposure time, astronomers detected over 600 young stars as point-like X-ray sources and diffuse X-ray emission from interstellar gas with a temperature of a million degrees. Infrared light observed with NASA's Spitzer Space Telescope shows cool gas and stars surrounded by disks of cool material.

By studying the distribution of the X-rays and their properties in W51 and combining this with data from other telescopes, astronomers are trying to better understand the details of how stars are born.