by Richard A. Lovett
Richard A. Lovett is a
Portland, Oregon-based science writer and science
He is a frequent contributor
SETI in the city:
astronomers are upping the ante
in the search for alien life.
SCIEPRO / Getty Images
The search for
is getting more
Astronomers looking for signs of extraterrestrial intelligence are
ramping up a host of new methods far more sophisticated than simply
turning radio telescopes to the stars in the hope of eavesdropping
on an alien civilization's chatter.
Not that people involved in the search for extraterrestrial
have given up on that approach.
A well-funded program
Breakthrough Listen is in the
process of studying radio emissions from a million stars and 100
galaxies, looking for just such transmissions.
But astronomers are also rushing to find ever-better ways to study
the thousands of
exoplanets being turned up by sky
searches, seeking not only to learn more about these planets'
geology, but also to find evidence that they may host life.
And while there might be a "giggle factor" in admitting to the
desire to turn the same powerful tools to the search for ET,
Adam Frank, an astrophysicist
at the University of Rochester, New York, US, says it's time to get
involved in this incredible hunt for bio-signatures," he said at
this week's AbSciCon 19 astrobiology conference in Bellevue,
"If you're looking
for bio-signatures, are you just going to pretend that you're
never going to be
looking for smart life, and
just looking for dumb life?"
Astrobiologists refer to
signs of "smart life" as
communications might be the easiest to detect, but there are many
others. For example, says Thomas Beatty, an astronomer at the
University of Arizona, Tempe, it's possible to search for the
lights of alien cities.
Earth-orbiting satellites have long been able to return images in
which our own urban "night lights" dazzle with both their sheer
beauty and the detail with which they trace the spread of
civilization across the globe.
Producing such images from interstellar distances, at which planets
appear as nothing more than dots in even the largest of present and
future telescopes, is currently beyond us.
lighting is different from sunshine and other forms of natural
light, because the technologies that produce it emit most of their
illumination in a narrow range of frequencies.
That, Beatty says, make them easier to spot from a distance.
For example, NASA's
LUVOIR space telescope should find
such lights easy to spot, if they exist, at least for planets
circling nearby stars.
"It's designed to
detect subtle atmosphere signals from the day side of earthlike
planets," he says. "That means it is capable of detecting
night-side city lights."
But it may not be
necessary to wait for LUVOIR's launch, not scheduled until 2039.
already under construction should be up to the task, Beatty says.
"We are very close to
being able to do technosignatures from the ground."
That said, there might be
easier technosignatures to spot than urban lights.
When we look at the stars, they seem to shine bright and steady
(other than twinkling effects created by the Earth's atmosphere).
But actually, says, Joseph Lazio, an astronomer at NASA's
Jet Propulsion Laboratory (JPL), Pasadena, California, that's
not the case.
On average, he says, at the nanosecond level (one billionth of a
second), a star's photons are few and far between. If you were to
take a nanosecond-level exposure of the sky, it's not likely you'd
see much of anything other than darkness.
Humans, on the other hand, are perfectly capable of building lasers
that emit intense pulses at the
femtosecond level (one millionth of
We can also build
narrow-band radar that emits signals unlike anything ever created by
nature and are capable to being detectable at interstellar
If we see something like that, he says,
"it is a reasonable
conclusion that technology is at work".
David Kieda, an
astrophysicist at the University of Utah, Salt Lake City, is already
using this method to search for "optical flashes" that might be
generated by distant civilizations.
His approach is to use data from gamma ray telescopes, which detect
gamma rays by the brief flashes of visible light they create as they
streak through the Earth's atmosphere.
These flashes, he realized, can be distinguished from laser-like
flashes from distant alien civilizations, due to the fact that gamma
ray flashes originate in the Earth's atmosphere, whereas alien
laser-flashes would come from much farther away.
That would alter the way in which they are seen by multiple
telescopes peering at them at the same time, with the gamma-ray
flashes hitting each telescope from a slightly different angle, and
extraterrestrial flashes coming in from too far way to show such an
So far, he says, no such extraterrestrial flashes have been found,
but to date, only a fraction of the available data has been
But that's just the beginning.
Svetlana Berdyugina of the Leibniz Institute for Solar
Freiburg, Germany, says it may even be possible to spot artificial
exoplanets, so long as they are large enough.
Doing this, she says, would start by studying variations in the
planet's brightness, called its "light curve", as it rotates first
one side, then the other toward us.
From that, she says, it's possible to map brightness variations on
the planet's surface - a technique that has long been used for
asteroids and other solar system bodies.
These maps could reveal the locations of continents, oceans, and ice
caps, but they might also show patterns that don't appear to be
natural, though to do that, the structures involved would have to be
truly huge - far beyond the scope of anything humans have yet to
"We've entered a
different era," says Frank. "It's no longer your grandfather's