NASA’S Hubble Space Telescope has looked deeper into the universe—and further back in time—than ever before. And it’s turned up a suite of galaxies that are new to astronomers. As announced by NASA on January 5, 2010, images of these distant galaxies are giving astronomers a rare peek at how the universe looked not long after the Big Bang.
These new galaxies were discovered in the most recent images of a long-term Hubble survey called the Ultra Deep Field. Last summer, the telescope reexamined the patch of the sky it had last glimpsed back in 2004. This time, however, a different set of galaxies was detected with the telescope’s new infrared camera. The camera captures incoming light in infrared wavelengths, which are longer than what our eye and typical camera lenses can see.
Because our Universe is expanding, these distant galaxies appear to be moving away from Earth. The farther away an astronomical object is, the faster that apparent motion occurs. The motion alters the appearance of the visible light emitted by the galaxies, which is why they have eluded astronomers for so long. The apparent motion elongates the wavelengths of light—called “redshifting”—making the visible light reach Hubble’s new camera as infrared light. (The process is identical to the Doppler effect, which causes the sound a motorcycle makes to deepen as it speeds away from us.) The amount of redshift astronomers observe tells them just how far away the object is.
The new Hubble images indicate that the galaxies are 13 billion light-years away. The light has taken 13 billion years to reach Hubble’s camera, which means we see the galaxies as they were 13 billion years ago—just 600 to 800 million years after the Big Bang. This time stamp will help astronomers study the evolution of the early Universe, including how the first stars formed and how galaxies grew from clusters of early stars. To see the most recent Ultra Deep Field image from Hubble, have a look at this week’s Astro Bulletin.