Have We Detected an
Alien Signal? It's Highly Doubtful
A blip of energy picked up by a Russian radio telescope might have
been nothing more than a satellite passing overhead—or even a
software glitch
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The VLA radio
telescopes in New Mexico Credit: By Hajor via Wikimedia Commons under Creative
Commons license
Based on
breathless news reports from many prominent media outlets that should know
better, this week’s biggest non-story in science is the discovery of a possible
radio signal from talkative aliens elsewhere in the Milky Way. I’m here to tell
you, alas, that anyone hoping for this to be the moment of First Contact with
another galactic civilization is very likely to be disappointed.
It all
started innocently enough, with a carefully worded blog post this past Saturday
from the respected science journalist Paul Gilster. Gilster wrote about a
message he had received from some SETI (Search for Extraterrestrial
Intelligence) researchers who reported a curiously powerful 3-second burst of
radio waves from a star less than 100 light-years away. The researchers,
led by Nikolai Bursov of the Russian Academy of Sciences, couldn't rule out the
possibility that the signal was artificial, and were intrigued enough that
they called for “permanent monitoring” of the star.
Gilster’s
post ignited a firestorm of sensationalistic and credulous news coverage that is still blazing as I write this, burning through newspapers
and websites to astound most everyone who encounters it. Soon, I predict, it
will burn out—as these sorts of stories (almost) always do.
Here's what
happened: in May of 2015, the RATAN-600 radio telescope in Zelenchukskaya,
Russia detected the signal from the direction of HD 164595, a star about 94
light-years away in the constellation Hercules. This is a star very much like
our Sun albeit slightly older, with an estimated age of 6.3 billion years. It
also harbors at least one known planet, an uninhabitable Neptune-sized
world, though of course others more habitable could exist in the system.
If the signal
really is artificial, and really does come from HD 164595, its energy
source must be gargantuan. According to Seth Shostak, an
astronomer at the SETI Institute in California who was not involved with the
research, a radio blast sent out in all directions by a hypothetical alien
civilization would take hundreds of times more power than that of all the
sunlight bathing the Earth, based on how bright the signal appeared in the
Russian telescope (that's because we'd only be seeing a tiny part of of the
total radio energy).
If it were
instead a beam focused solely on the Earth, the signal would still
require twice the electricity used by the United States in an entire year.
Clearly, if this is another galactic civilization, they are far, far more
advanced than our own.
The trouble
is, there is no good reason to think that this signal is due to aliens at
all—and there never was, according to Eric Korpela, an astronomer at the
University of California in Berkeley. Korpela heads SETI@Home, a
citizen-science initiative that processes SETI data using home
computers; on the SETI@Home blog, Korpela
said that after evaluating the available evidence he was “unimpressed” and that
the data was “relatively uninteresting.”
“SETI@home
has seen millions of potential signals with similar characteristics, but it takes
more than that to make a good candidate,” Korpela continued. “Multiple
detections are a minimum criterion.”
That's not
what the Russian telescope found. The putative signal only occurred once out of
39 times the RATAN-600 telescope scanned the star, and the scans themselves
were performed in such a way that many potential false positives could not be
ruled out.
Rather than
being a beacon from ET, Korpela said, the signal could just as easily have been
due to flares from the target star, the burp of a supermassive black hole in a
background galaxy, or even the chance magnification of ordinary, all-natural
stellar radio emissions by a passing foreground star or a transient ripple of
interstellar plasma.
What this
boils down to is that extraordinary claims require extraordinary
evidence—evidence that can be very hard to come by for modern SETI programs.
Contrary to
Hollywood depictions, SETI efforts tend to have meager budgets that only
support infrequent observations of small fractions of the sky in narrow
bandwidth ranges. Could the new signal from HD 164595 be a genuine transmission
from a cosmic civilization? Well, yes, conceivably it could. But so could the
millions of other curious optical blips and radio spikes sitting in SETI
archives, each a singular phenomenon that whispered just once into a telescope,
never to repeat or return. This has happened before—see, for instance, the
tantalizing “Wow! signal” from 1977,
and the resulting decades of fruitless efforts see it a second time.
Even assuming
there was enough telescope time available (there isn’t), every SETI program on
Earth would likely go bankrupt trying to follow-up each of the millions of
potential candidates if each received the care and attention bestowed upon the
Wow! signal. In such a resource-constrained environment, only the very
best and most compelling signals should merit much closer attention—and Korpela
isn’t sure the signal from HD 164595 has crossed that threshold.
The real
problem, Korpela goes on, is that the media frenzy over HD 164595 means that no
reputable SETI program can now afford to not use precious telescope time to
look for other signals from HD 164595. These projects need money, and they need
public attention—ignoring the signal even if it is overwhelmingly likely to
prove spurious is not an option. “We’ll be along for the ride,” he wrote. “And
we’ll all find nothing.”
Indeed,
according to Shostak, the SETI Institute’s Allen Telescope Array is already
looking at the star, though so far they have yet to see anything peculiar.
Other results
are now coming in. Just this morning the Breakthrough Listen project, a private
SETI endeavor funded by the billionaire Yuri Milner, released results of a follow-up on HD
164595 using archival data as well as new observations from the Green Bank
Telescope in West Virginia. Breakthrough found—you guessed it—nothing.
More
curiously, Breakthrough’s statistical analysis of the available data suggests
that, if produced by natural astrophysical causes, one would expect that
previous surveys would have seen such strong signals elsewhere in the sky.
Which means
that the RATAN-600 team was “either extremely lucky to detect this source in
their observations, or that the transient is due to local interference or other
calibration issues.” That is, absent the possibility of aliens, even an
astrophysical source for the signal looks suspect—a far more likely explanation
for the signal would be the passage of a satellite overhead, or an errant
signal from electric currents coursing through wires within the observatory
itself, or even a software glitch.
Nevertheless,
the Breakthrough Listen team intends to periodically revisit HD 164595 in the
future to keep looking for a repetition of the signal. Other SETI programs will
undoubtedly do the same. And perhaps they should. But let’s not fool ourselves:
Even in the lofty, noble quest to break our cosmic solitude, sometimes the tail
can wag the dog.
Now if you’re interested in a truly epochal
discovery relevant to the search for extraterrestrial life,
I would refer you to last week’s announcement of a
rocky planet found in a habitable orbit around the Sun’s nearest neighboring
star, Proxima Centauri—which frustratingly seems to have made less of an
impression than this week’s far more questionable news.
Lee Billings
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Lee Billings
is an editor at Scientific American covering
space and physics.
Nick Higgins
SOURCE….Sky and Telescope
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