The only way to study how young galaxies develop is to look back in time--that is, to look as far away as we can see, because the light from those distant galaxies will have taken billions of years to travel to us, and thus offers a snapshot of the early universe.

In December, 2007, astronomers published these two photos--the left in visible light and the right in infrared--which offer a glimpse of a galaxy called GOODS 850-5, 12 billion years ago. At this point, only 1.5 billion years after the big bang, the galaxy was forming stars at a furious pace, about 4,000 a year. Astronomers were surprised to find such a high rate of star formation in a galaxy so young; it means that galaxies might have developed much faster than previously thought.

GOODS 850-5, in the white circle, is visible only in the infrared photo because its visible light is obscured by dust in the galaxy. The hot young stars heat up the dust, which then emits the infrared radiation that we see.