High resolution poster version
Generations of stars can be seen in this new infrared portrait from NASA's
Spitzer Space Telescope. In this wispy star-forming region, called W5, the
oldest stars can be seen as blue dots in the centers of the two hollow
cavities (other blue dots are background and foreground stars not
associated with the region). Younger stars line the rims of the cavities,
and some can be seen as pink dots at the tips of the elephant-trunk-like
pillars. The white knotty areas are where the youngest stars are forming.
Red shows heated dust that pervades the region's cavities, while green
highlights dense clouds.
W5 spans an area of sky equivalent to four full moons and is about 6,500
light-years away in the constellation Cassiopeia. The Spitzer picture was
taken over a period of 24 hours.
Like other massive star-forming regions, such as Orion and Carina, W5
contains large cavities that were carved out by radiation and winds from
the region's most massive stars. According to the theory of triggered
star-formation, the carving out of these cavities pushes gas together,
causing it to ignite into successive generations of new stars.
This image contains some of the best evidence yet for the triggered
star-formation theory. Scientists analyzing the photo have been able to
show that the ages of the stars become progressively and systematically
younger with distance from the center of the cavities.
This is a three-color composite showing infrared observations from two
Spitzer instruments. Blue represents 3.6-micron light and green shows
light of 8 microns, both captured by Spitzer's infrared array camera. Red
is 24-micron light detected by Spitzer's multiband imaging photometer.
