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Franck MarchisAugust 30, 2016

Let’s be careful about this “SETI” signal

This post originally appeared on Franck Marchis' Cosmic Diary blog and is reposted here with his permission.

Several readers have contacted me recently about reports that a group of international astronomers have detected a strong signal coming from a distant star that could be a sign of a high-technology civilization. Here’s my reaction: it’s interesting, but it’s definitely not the sign of an alien civilization—at least not yet.

The Allen Telescope Array - timelapse at night with Milky Way

SETI Institute

The Allen Telescope Array looks for signals from among the stars.

Here’s why:

  1. The signal was first detected in May 2015 and has not repeated since. Unfortunately, although international protocols call for alerting the astronomical community to the detection of a mysterious signal, the observers chose not to do so. Sadly, their failure to observe this simple protocol likely hindered our ability to clarify exactly what caused the signal.
  2. The signal was detected by an antenna that is very complex—and one that a colleague of mine who is a radio astronomer said could have mislabeled a terrestrial signal (i.e, one from a satellite or airplane) crossing the side lobes of the beam when the observation was made. In other words, the pointing quality of this antenna is so uncertain that it may have captured what we call a false or “parasite” signal.
  3. HD 164595, the host star, is very similar to the sun (same color, size, and age). It’s ninety-one light years from Earth and has a known planet, HD164595 b, which is probably Neptune-like and orbits very close to its star every forty days. We have not yet detected an Earth-like or super-Earth-like planet around this star, and do not believe there is one. This is the case because this is what current theories on the formation of planetary systems tell us. But there is no reason why life could not exist on satellites of as-yet undetected icy giants in this system—but this moves us from fact to the realm of pure speculation.
  4. Finally, before getting too excited about a speculative and relatively old signal, we should recall the puzzle of the perytons. Astronomers detected them at the Parkes Observatory in Australia in 2015, only to later conclude that they were nothing more than the signal from a nearby microwave oven whose door was opened by impatient astronomers.

But—and it’s a big but—I began this post by saying “at least not yet.” So what might cause me to change my mind? How might we prove the extraordinary claim that this signal is, in fact, a civilization trying to communicate with us?

We turn to this mantra from Carl Sagan: “Extraordinary claims require extraordinary evidence.” That means three things:

First, this signal must be detected by at least one other antenna located somewhere else in the world. My colleagues at the SETI Institute are already working on it, and have observed the star for several hours. So far they have nothing to report.

Observing the latest star of interest - HD164595 - with the Allen Telescope Array. #ATASETI

— Jon Richards (@jrseti) August 29, 2016

Second, we must analyze the signal to be certain that it is not coming from a human source.

Third, if the signal is detected repetitively, we can analyze it under the assumption that it might have content E.T. wants to share with us. Whatever that message might be—the digits of Pi, the first prime number, their encyclopedia, or some images of themselves—we can quickly find out if ET is trying to tell us something, and what that something is.

We are not there yet. In the past, especially during the tumultuous history of SETI, astronomers briefly thought that they had discovered a signal (see “Aliens on Line 1”). As technology evolves, and more searches occur, we may discover more signals that look promising at first but don’t pan out. But the search continues… in fact, in the scale of the age of our solar system, it has just begun.

Read more: explaining science, SETI

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Franck Marchis
Franck Marchis

Exoplanets Research Thrust Chair for SETI Institute
Read more articles by Franck Marchis

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