Space Telescope Science
In Arthur C. Clarke's novel "2001: A Space Odyssey," astronaut David Bowman exclaims, "My God, it's full of stars!" before he gets pulled into an alien-built wormhole in space. When the Hubble Space Telescope made its deepest views of the universe, astronomers might have well exclaimed: "My God, it's full of galaxies!" The Hubble Ultra Deep Field, for example, revealed 10,000 galaxies of various shapes, sizes, colors, and ages, all within an area roughly one-tenth the diameter of the full moon. What's mind-blowing is that these myriad galaxies, though plentiful, may represent merely 10 percent of the universe's total galaxy population. That's according to estimates from a new study of Hubble's deep-field surveys. The study's authors came to the staggering conclusion that at least 10 times more galaxies exist in the observable universe than astronomers thought.
According to the authors, the missing 90 percent of the universe's galaxies are too faint and too far away to be detected by the current crop of telescopes, including Hubble. To uncover them, astronomers will have to wait for much larger and more powerful future telescopes. The researchers arrived at their result by painstakingly converting Hubble deep-field images into 3-D pictures so they could make accurate measurements of the number of galaxies at different epochs in the universe's history.