Galaxy hunters vie in distance contest
Let others pursue the fattest grouse or the most gigantic buck. A new breed of 21st-century hunters is on the chase, their weapon the most advanced telescopes, their prey bigger than the solar system.
For the past few years, scientists have engaged in a fierce competition to bag the most distant galaxies in the cosmos —galaxies that existed less than a billion years after the Big Bang, the colossal explosion that founded the universe. Records have been set, broken and broken again, while astrophysicists joust over which early galaxies are real and which are embarrassing errors.
The contest is more than a “fast and furious race,” as one scientific paper called it. The quest for the farthest galaxies has shed light on the evolution of the young universe, but now researchers hope to pinpoint the onset of “cosmic dawn,” when starlight from newborn galaxies first bathed the universe.
Snaring a distant galaxy is a lot harder than bagging the most elusive game. The farthest galaxies are, to human eyes, “literally invisible,” says University of Texas-Austin astrophysicist Steven Finkelstein, whose team holds one distance record. He explains that when light from far-off galaxies travels to telescopes in our neck of the cosmic woods, any visible light is transformed along the way into a light “redder than our eyes can see,” though it's visible to the right kind of cameras and telescopes.
Such “redshifted” light spends billions of years journeying to the vicinity of Earth. The information encoded in the light gives scientists a picture of galaxies as they were billions of years ago — essentially the baby pictures of the universe. The farther away the galaxy, the further back in time we see.
For years, scientists could peer back no further than about 12 billion years ago, when the universe was about 780 million years old. Finally, in 2009, astronauts fitted the Hubble Space Telescope with a new camera, called Wide Field Camera 3, that revolutionized the galaxy-hunting business. Wide Field 3 is far more efficient than its predecessor on the Hubble, and it can see very red light, just the right color for detecting the most distant galaxies.
Researchers have discovered about 200 galaxies that were in existence less than 780 million years after the Big Bang, according to research by astrophysicist Garth Illingworth of the University of California-Santa Cruz and his colleagues.
Though there's still much to learn, Hubble can't help much more. Researchers are waiting eagerly for the opening of an array of ground-based telescopes and for the 2018 launch of NASA's James Webb Space Telescope, which should allow researchers to detect galaxies not long after the Big Bang.