September 8, 2006
This image from NASA's Spitzer Space Telescope reveals the complex life cycle of young stars, from their dust-shrouded beginnings to their stellar debuts. It shows a nursery of stars 21,000 light-years away in the Cepheus constellation.
A star is born when a dense patch of gas and dust collapses inside a cosmic cloud. In the first million years of its life, a star is hidden from visible-light view by the cloud that created it. Eventually, as the star matures, its strong winds and radiation blow away surrounding material, and the star fully reveals itself to the universe.
The first stages of stellar life are represented by the greenish-yellow dot located in the center of the image (just to the right of the blue dot). Astronomers suspect that this star is less than a million years old, because it is still deeply embedded inside the cosmic cloud that collapsed to form it. Wisps of green surrounding the star and its nearby environment indicate the presence of hot hydrogen gas.
Above and to the left of the central greenish-yellow dot, a large, bright pinkish dot reveals a more mature star on the verge of emerging from its natal cocoon. Although this star is still shrouded by its birth material, astronomers use Spitzer to see the surrounding gas and dust that is being heated up by the star.
The region's oldest and fully exposed stars can be seen as bunches of blue specks located just left of the concave ridge. Energetic particles and ultraviolet photons from nearby star clusters etched this arc into the cloud by blowing away surrounding dust and gas.
The image is a four-channel, false-color composite, where blue indicates emission at 3.6 microns, green corresponds to 4.5 microns, and red to 5.8 and 8.0 microns. The image was taken by Spitzer's infrared array camera.