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Let
there be light
Berkeley
astronomers launch new optical search for intelligent life
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Two
dazzling clusters of stars in a neighboring galaxy
like this one could harbor intelligent life. Hubble
Space Telescope Science Institute image, July
10, 2001
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Full SETI Institute news release |
Slide show | Related links
By
Diane Ainsworth
Public Affairs
They've
been listening for more than four decades for a whisper
from an intelligent civilization light years away. Now a team
of astronomers in the Bay Area is looking for winking
stars—blinking pinpoints of light in the night sky that
appear to be deliberate signals, possibly sent from an intelligent
civilization living nearby.
UC
Berkeley scientists Daniel Werthimer and Richard Treffers
have joined an effort by the UC Lick Observatory, UC Santa
Cruz and SETI Institute in Mountain View, Calif., to use Lick's
freshly upgraded 40-inch Nickel Telescope to conduct the new
optical search for intelligent life in the universe. The latest
experiment augments radio astronomy surveys that have been
scouring the heavens for decades in search of intelligent
life. The Lick Observatory hunt for winking stars is one of
only a handful of optical SETI (Search for Extraterrestrial
Intelligence) programs under way at universities and institutions
across the country.
"This is perhaps the most sensitive optical SETI search yet
undertaken," said Frank Drake, chairman of the board of the
SETI Institute and a co-investigator on the new experiment
(http://www.seti.org/).
Drake, who in 1960 conducted the first modern hunt for evidence
of extraterrestrial intelligence, is usually associated with
radio SETI, an approach in which large antennas are connected
to specialized, multi-million channel receivers. "This is
different," he noted. "We are looking for very brief but powerful
pulses of laser light from other planetary systems, rather
than the steady whine of a radio transmitter."
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Shelly
Wright, architect of the 40-inch Nickel Telescope's new
detector instrument, has some fun after a successful installation.
Photo © Laurie Hatch |
The
newly refurbished Nickel Telescope light-detector instrument
system—a three detector instrument upgrade that has almost
virtually eliminated the false signals that plague most radio
astronomy searches—seems to be outshining its predecessors:
two-detector instrument systems, Werthimer added.
"False
alarms are naturally emitted flashes of light that can be
mistaken for artificial signals being intentionally sent by
aliens tens or hundreds of light years away," he said. "One
of the primary advantages to an optical search is that it's
hard to mistake a natural from an artificial light pulse.
We can look at thousands of stars without confusing natural
light beams from artifacts of someone's technology, like a
laser beacon, or with reflections that might be coming from
an airplane or a satellite or light pollution."
The
program, which is operated by UC Santa Cruz, with major participation
from UC Berkeley, takes advantage of today's powerful laser
technology to search for bright pulses that arrive in a short
period of time (less than a billionth of a second). Of course,
light from the central star will trigger the detectors as
well, but seldom will all three light-tube detectors (photomultipliers)
be hit by photons within a billionth of a second time frame,
the astronomers said. Although still in their infancy, these
types of optical programs, which are relatively inexpensive
to run, seem to be catching on. In addition to the Lick Observatory
program, Harvard University, Princeton, the Columbus SETI
Optical Observatory in Ohio and Berkeley all operate optical
sky surveys.
"Right
now we can outshine our own sun with the powerful lasers we
have today," Werthimer said, "and we can do that for a billionth
of a second or so. So, if we can do that, the chances are
with us that other civilizations can do that too."
Roughly
200 billion stars rest in the spiraling arms of the Milky
Way galaxy alone, just waiting to be observed, and at least
12 billion solar systems probably harbor planets, not unlike
the gaseous giants and terrestrial worlds of our own planetary
neighborhood. The sheer numbers of celestial targets are enough
to make eager astronomers cringe at the thought of wasting
time on unclear signals or ambiguous spikes in the data that
would require a second look.
The
$28,000 experiment, which included about $10,000 in hardware
expenses, was initiated after the instrument itself was finished.
Its architect, Shelley Wright, was an undergraduate student
at UC Santa Cruz, finishing up her degree in physics. Her
three-detector instrument turned out to be a vast improvement
over two-detector instruments used on telescopes to conduct
optical searches, said Remington Stone, the Lick Observatory
optical SETI program principal investigator.
"The
detectors will count about one out of every five photons,
or about 20 percent of all of the incoming photons from the
light being observed, so they're not terribly sensitive, but
they are exceedingly fast," he said. "But it's not often that
all three of the detectors will be hit by photons (electromagnetic
radiation) arriving in the brief interval of a billionth of
a second."
Astronomers
said the new detector system will produce far fewer ambiguous
results: the chances of mistaking starlight, cosmic rays,
muon showers and radioactive decays in the glass of the photomultiplier
tubes are likely to happen only about once a year, Werthimer
said.
The
idea of searching the heavens for laser flashes goes back
40 years, to UC Berkeley physicist Charles Townes, who was
a recipient of the Nobel Prize for inventing the laser. Because
radio astronomy was a more mature technology, though, the
technique wasn't systematically applied until four years ago,
when the first sustained search for optical pulses was launched.
Now
several months into the search, the team is observing normal
types of stars, like Earth's own sun, that are within 200
light years of the planet and at least as old as our sun.
Graduate student observers like Paul Demorest, a Berkeley
graduate student in physics, have contributed their expertise
to the experiment with the development of computer software
to operate the Nickel Telescope. The program averages about
one full night of observing time each week and, according
to Demorest, will target other celestial objects, such as
stars that are hotter and cooler than the sun, because they
are more likely to support life.
More
than 600 stars have already been observed, each for about
10 minutes, which is all the time that is necessary to detect
the strobe lights of a distant message from intelligent life.
But the number of stars on the waiting list is quite a bit
more ambitious, totaling somewhere in the neighborhood of
about 5,000, said Seth Shostak, an astronomer at the SETI
Institute.
"Those
are just the nearby stars, only a tiny fraction of the galaxy,"
he said. "This is all unexplored territory, but optical searches
are definitely the new kid on the block and they're proving
to be very interesting."
Related
Links:
http://www.ucolick.org/
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