This artist's animation demonstrates that an invisible galaxy shrouded in dust can become glaringly bright when viewed in infrared light. The movie begins with a visible-light view, showing a dark blob of a galaxy that is so shrouded in dust it appears invisible. The picture then transitions to what the same region of space might look like in infrared light. A galaxy appears out of the darkness, because its heated dust glows at infrared wavelengths.
NASA's Spitzer Space Telescope uncovered a hidden population of invisible galaxies like these using its highly sensitive infrared eyes. The dusty galaxies are among the brightest in the universe and are located 11 billion light-years away, back to a time when the universe was 3 billion years old. The universe is currently believed to be 13.5 billion years old.
Astronomers are not sure what is lighting up these cosmic behemoths, but they speculate that quasars--the most luminous objects in the universe--may be lurking inside.