Let others pursue the fattest grouse or the most massive 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.
the past few years, scientists have been 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.
Holy Grail right now is to find that moment and to find the very
earliest galaxies," says astrophysicist Richard Ellis of Caltech. "We've
been pushing the frontiers further and further back."
Snaring a distant galaxy is a lot harder than netting the most
elusive fish. The farthest galaxies are, to human eyes, "literally
invisible," says the 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.
are time machines (that) let us peer back into the past," says
astrophysicist Garth Illingworth of the University of California-Santa
Cruz, via e-mail. "The light from distant objects takes so long to reach
us that we see them when they were much younger."
scientists could peer back no further than roughly 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.
When Wide Field 3 produced its first batch of data in 2009,
competing groups of scientists pounced on it and quickly found dozens of
galaxies much deeper in time than seen before.
serious scientific objectives in seeking out distant objects, but
there's also "the thrill of the chase," agrees Illingworth in an
interview. "We do love getting the highest redshift one" - meaning the
farthest galaxy - but "you're lucky if the record lasts for six months.
Then you've got to go back and do it again."
"There has to be a
scientific reason for doing it. Otherwise it's just a stunt," astronomer
Mark Dickinson of the Tucson-based National Optical Astronomy
Observatory says of hunting distant galaxies. But "there's the
horse-race aspect of it, and that's good fun."
discovered roughly 200 galaxies that were in existence less than 780
million years after the Big Bang, according to research by Illingworth
and his colleagues. Along the way, researchers have relentlessly pushed
back toward the beginning of it all. At first, the farthest galaxies
detected were at 650 million years since the Big Bang, then only 500
million years, and now even 450 million years or less, though those
figures are the subject of debate.
The problem is that the
competition, and the difficulty of trying to identify star clusters
billions of miles away, can lead to mistakes.
"There are plenty of cautionary tales out there about distant
galaxies that have proven to be wrong," Finkelstein says. There's the
galaxy reported, to great fanfare, at roughly 600 million years after
the Big Bang, a date since proven wrong. Or the record-holder estimated
at a mere 380 million years, which scientists refer to as having a
"redshift" of 11 or 12, that new research shows may actually be at just
under 3,300 million years after the Big Bang.
"The jury may still
be out" on that one, says Arizona State University astrophysicist James
Rhoads, "but to be honest, I'm putting a case of beer against redshift
While debate continues on the record-holder, everyone can
agree that the distant galaxies amassed so far have helped illuminate
the childhood of the universe. For example, scientists now believe that
the hydrogen fog that permeated the early universe was cleared by the
starlight from "huge numbers of really rather faint, small galaxies,"
not a few ultra-large galaxies, Illingworth says. "This was somewhat
unexpected." He describes the galaxies at that time as close-packed,
perhaps colliding with one another to trigger bursts of star formation.
one were back there, it would be a very different sight looking out
into the night sky," he says. "You'd see small, bright, blue clumps all
over the place."
Though there's still much to learn, Hubble can't
help much more. It has looked about as far back as it can possibly see,
and now researchers are waiting eagerly for the opening of an array of
new 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.
"We won't be satisfied until we get there," Ellis says. "We need to go just that little bit further back, and we're very close."