August 19, 2009--
Ultraviolet telescopes have upended a long-held theory of the cosmos: that bundles of stars have a size limit.
According to the theory, for every single, massive star only a fixed number of smaller stars exist nearby. But the above photographs, made by combining data from NASA's Galaxy Evolution Explorer spacecraft and the Cerro Tololo Inter-American Observatory in Chile, revealed that much larger bundles of little stars do exist, they were simply being masked by huge, brighter stars.
The spiral galaxy on the left, dubbed NGC 1566, is richer in massive O stars (white or pink) but doesn't have that many smaller B stars (blue). But the galaxy on the right, called NGC 6902, has many more B stars than it does O stars.
Image courtesy NASA/JPL-Caltech/JHU