A telescope
on the far side of the moon could probe the "dark ages" of the
universe while blocking out the radio-wavelength noise of Earth civilizations.
Up to one
hundred thousand antennas would form the Dark Ages Lunar Interferometer (DALI),
the largest telescope ever built, and allow astronomers to hear faint
whispering signals from a time when no stars even existed.
"This
will look at one of the most fundamental questions ever conceived, back when
the universe was made up almost entirely of hydrogen and helium — no
stars, no galaxies," said Kurt Weiler, senior astronomer at the U.S. Naval
Research Laboratory.
The
so-called dark ages
of astronomy describe a half-billion year period following the Big Bang when
clouds of ionized gas cooled as the universe expanded. The only faint noise came
from hydrogen atoms doing spin-flips, which gives off radio-wavelength signals
that astronomers can pick up on. Scientists currently estimate that the
universe is about 13.7 billion years old.
"What
happens is that because of the Big Bang there's a background glow," Weiler
noted. "The spin-flip will absorb the glow of the older material and will
give us a signature that we can see."
However, the
ongoing
expansion of the universe has stretched or red-shifted the hydrogen signature
from just 21 centimeters to several meters. That means the signals can easily
get masked by louder Earth transmissions in the same wavelength, unless
astronomers find a quieter listening spot.
"The
back side of the moon is the only
place in the local universe shielded from manmade transmissions," Weiler
told SPACE.com.
The DALI
design resembles existing radio
telescope arrays in the Netherlands, Australia, and New Mexico. But sending such an array to the moon requires lighter
material that can save on launch costs, not to mention survive the harsh lunar
conditions.
One
candidate is polyimide, a plastic-like film which can act as an antenna when
plated with metal. University of Colorado researchers are testing the film's durability by exposing
it to harsh ultraviolet rays, as well as the extreme temperatures like that of
boiling water and super-cold liquid nitrogen.
The film
antennas would be rolled up and then unrolled for deployment across 30 miles
(48 km) of lunar surface, arrayed in one thousand stations containing one
hundred antennas each. Still, getting the entire load to the moon represents a
challenge.
"Even
though each antenna may weigh a few ounces, you're talking about needing at
least heavy lift vehicles," Weiler noted. "They all add up fast."
The U.S. Naval
Research Laboratory is sharing NASA funding with an MIT-based team working on
another lunar telescope separate from DALI. Their collaboration may finally
realize a dream that many astronomers had even before the first Apollo landings
on the moon.
"Probing
the dark ages presents the opportunity to watch the young Universe evolve," said
Joseph Lazio, NRL astronomer and head of the DALI proposal. "Just as current
cosmological studies have both fascinated and surprised us, I anticipate that
DALI will lead both to increased understanding of the Universe and unexpected
discoveries."
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