Astronomers
are planning a massive 250-foot telescope that will search for
extraterrestrial life by detecting the heat that alien civilizations may
produce.
The proposed instrument -- called
Colossus -- would measure 77-metre, which is more than double the
aperture of any telescope yet constructed. It is expected to cost $1
billion.
The telescope would be sensitive
enough to spot cities or other signs of aliens for planets as far as 60
to 70 light-years from Earth, astronomers said.
"If
we had an investor come and say 'look, here are the resources you
need', we could have the telescope built within five years," said Jeff
Kuhn, an astronomer at the University of Hawaii's Institute for
Astronomy, who is on the proposal team.
In
searches for extraterrestrial intelligence, astronomers generally focus
on seeking out beamed signals from other civilisations. In four decades
of searching, nothing definitive has been found, Space.com reported.
There
are limitations with this method, however. Perhaps the aliens might not
send out signals themselves. Perhaps they broadcast in channels humans
wouldn't think of using.
Moreover, humans
should perhaps be cautious about sending out signals and alerting more
advanced civilisations to their presence, as physicist Stephen Hawking
has said.
This is where Colossus can shine,
Kuhn said. The telescope is a passive receiver that allows astronomers
to seek out extraterrestrials without alerting them to the search.
Kuhn's
team builds on a concept first proposed by physicist Freeman Dyson in
the 1960s. Humans can capture only a fraction of the energy sent out by
the Sun, but a more advanced civilisation would want to grab as much as
possible.
Dyson suggested an extraterrestrial
civilisation would surround their star with a structure - now known as a
"Dyson sphere" - that would capture the energy needed and then bleed
the rest off into space.
From Earth, a star
that is faint optically but very strong in the infrared could be an
indication of such a sphere, Dyson mused.
Kuhn's team, rather than focusing on stars, is instead looking at the surfaces of alien planets.
"Similarly,
an exoplanet that was optically dark, but thermally bright, would be
evidence of extraterrestrial civilisation," Kuhn said.
"The
biggest telescopes that we're likely to see in the next 100 years or so
will not be able to directly image cities or organised structures on
the planet," he said. Still, he added, local heat sources could be
visible.
There's no firm location yet for the
telescope, but Kuhn suggested it could be built in the San Pedro Martir
mountainous area of Baja California in Mexico, close to the location of
one partner in the project: the National University of Mexico in
Ensenada.
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