The nebula M17, known as the Swan, Horseshoe or Omega Nebula, lies between 5,000-6,000 light years from Earth in the direction of the constellation of Sagittarius. It spans 15 light years and contains around thirty-five million year old stars lighting up the remains of the gas from which they formed. As the light from the stars ionises the gas in the nebula, converting hydrogen to H+, it is known as an HII Region, where HII is the astronomical designation for H+.
New results from the Spitzer Infrared Space Telescope have added to details on the region surrounding this vast reservoir of gas and dust. To the left of M17 on the image lies M17 EB, an area of space that shows what will eventually happen to M17. In it, a series of stars aged two to five million years old have evacuated a bubble in space by forcing away gas and dust through strong stellar winds and radiation pressure. This bubble has extended to the point where it is now impacting on the left hand side of M17 itself.
To the right lies another, earlier stage of development. In a vast tranche of cool, dark gas called M17 SWex, only readily visible in infrared where the cool things glow, Spitzer identified 488 new stellar cores developing their way into fully fledged stars. Given the density of the dark stuff and the distribution of the stars, this means there could be up to 10,000 stars within the stellar nursery.
This ages of star image has been described by NASA as looking like a dragon flying from a fiery cloud, though I notice in their visible light image, M17 itself looks like a dragon rising phoenix-like upward from flames, wings extending, chest lit up.