ROOM
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Space Science
as fine as 1 Hz - and hunt for signals using these
instruments on existing radio telescopes. The
search strategy was two-pronged: to scan the
entire visible sky at relatively low sensitivity, and
to zero in for a more intensive examination of
approximately 1,000 nearby star systems. Although
the programme cost less than 0.1 percent of
the NASA budget, this effort was killed by the
US Congress a year after observations began,
ostensibly for reasons of economy.
Since then, experiments have continued
primarily at the SETI Institute in the Silicon
Valley and at the University of California Berkeley.
Funding has been via private donations, and the
combined annual effort runs at approximately
three percent of the cost of a single Ariane 5
launch. It is also worth noting that, at present,
only the United States has any dedicated SETI
programmes. Despite the seductive excitement of
proving that there are other beings in the cosmos,
the actual effort to do so has been disappointingly
limited. That, however, may change.
New approaches
Today, there is increased enthusiasm for SETI.
While this is partially due to the surge in
planetary discovery, there are also improvements
in technology that can broaden the search and
increase its speed.
Larger radio telescopes, including the new FAST
500 m radio telescope in China and the Square
Kilometre Array being built in South Africa and
Australia, will increase our sensitivity to signals.
In addition, the unremitting march of digital
technology has allowed more of the radio
spectrum to be sampled in a given amount of
time. For radio telescope arrays, additional
computational power can be used to ‘look’ at
several patches of sky simultaneously. And the
emergence of machine learning is offering the
opportunity to hunt for an unlimited number of
signal types. Past experiments could recognise
only a few.
These improvements are seldom appreciated
by the general public, which imagines SETI as it is
portrayed in the movies. In the Hollywood version,
a lone researcher with headphones strains to hear
anything vaguely odd. That depiction was never
‘true’; computers long ago took over the ‘listening’.
And computers are much better listeners – they
can find weaker signals and check out more of
the radio spectrum. Indeed, because of the rapid
improvement in the speed of computers, it should
be possible to examine approximately a million
star systems for artificial signals in the next two
decades. That’s two to three orders of magnitude
more than were targeted during the first half-
century of SETI.
California’s SETI Institute is getting a head start
on these far larger cosmic surveys by conducting
a programme using its own instrument, the Allen
Telescope Array. The array will observe 20,000 red
dwarf star system over a small number of selected
frequency ranges in the next two years.
Red dwarfs – stars that are both smaller and
dimmer than the Sun – were traditionally of
little interest to SETI researchers. They aren’t
like the Sun, the only star known to harbour a
world with intelligence. But recent exoplanet
studies have shown that a considerable fraction of
these bantam suns have planets in the so-called
‘habitable zone’ – an orbital distance at which
temperatures could be suitable for liquid-water
oceans. Red dwarfs also have the advantage of
enjoying extremely long lifetimes – 10 times that
of a Sun-like star. So, on average, they are several
billions of years older. That is an obvious plus point
when looking for intelligent life, which on Earth
The Allen Telescope
Array (ATA) is a ‘Large
Number of Small Dishes’
(LNSD) array designed to
be highly effective for
simultaneous surveys
undertaken for SETI
projects at centimetre
wavelengths.
The Arecibo
Observatory radio
telescope in Puerto Rico
has been used for SETI
work many times.
The rapid
improvement
in computer
speed means
it should
be possible
to examine
around a
million star
systems for
artificial
signals in
the next two
decades
