The blip

In 2010 the Search for Extraterrestrial Intelligence (SETI) program detected a powerful radio signal of some interest.  The signal came from the direction of a star designated TYC 1220-91-1, which is very similar to our own Sun, though older; if other habitable planets like Earth exist in the universe at all, this star would be a good candidate to have one.  It's about 100 light-years away (to give you an idea of what that means, the outermost body in our own solar system, Pluto, is so far from Earth that the New Horizons probe launched toward it in 2006 will not get there until 2015, and TYC 1220-91-1 is about two hundred thousand times further away than Pluto).

The signal, however, was clearly not an attempt at communication by aliens, which is what SETI is interested in.  It had no internal structure suggesting encoded information, and it lasted just ten seconds and did not repeat, as a deliberate effort to communicate almost certainly would.  So what was it?  A blogger "Jadestar" has an idea.

At Arecibo in Puerto Rico, the US maintains a huge radio telescope which can also be used as an interplanetary radar station.  In this capacity, it works like ordinary radars which send radio signals that bounce off solid objects like airplanes and are reflected back to the transmitter, enabling those objects to be detected.  Arecibo, however, monitors asteroids in the inner solar system, enabling scientists to track their orbits and find out if any of them pose a risk of colliding with Earth at some time in the future.  Its radar signals are very powerful and focused -- among the most powerful radio signals ever generated on Earth.

If you were 100 light-years from our solar system, and Arecibo just happened to be aimed in exactly your direction while it was doing a radar scan for asteroids here, the radio pulse you would detect would look a lot like the one SETI picked up coming from TYC 1220-91-1.

So.  Maybe there's an Earthlike planet orbiting TYC 1220-91-1.  Maybe it has something like the Arecibo radio telescope on it.  Maybe they sometimes use that telescope to scan their inner solar system for dangerous asteroids, like we do.  And maybe, by pure chance, their radar transmitter happened to be pointing in exactly our direction for a few seconds.

If that's what it was, we'll never know for sure.  The odds of that exact alignment ever happening again are essentially zero.  If they use radio telescopes similar to ours, their general level of technological development is probably roughly similar to ours, and there's almost nothing a civilization like that does that would be detectable at such a distance -- ordinary radio and TV transmissions fade out in less than two light-years.  That one radio blip is all we're going to get.

Now, as I've expressed before, I think it's actually unlikely that intelligent life exists elsewhere in the universe.  But our knowledge is too incomplete for any such view to be more than tentative.  The radio blip could well have been produced by some natural phenomenon we haven't discovered yet.  But it just might have been a sign, even if faint and accidental, that other minds exist.

[Jadestar link found via Mendip.]