As far as interesting problems go, few can really compete with the perennial question: “Are we alone?” The need to know if there are other forms of intelligent life out there in the galaxy is deeply rooted, and knowing for sure either way would have massive implications.
But it’s a big galaxy, and knowing where to look for signals that might mean we’re not alone is a tough task. Devoting limited and expensive resources to randomly listen to chunks of the sky in the hopes of hearing something that’s obviously made by a technical civilization is unlikely to bear fruit. Much better would be to have something to base sensible observations on — some kind of target that has a better chance of paying off.
Luckily, a chance observation nearly 50 years ago has provided just that. The so-called Wow! Signal, much discussed but only occasionally and somewhat informally studied, has provided a guidepost in the sky, thanks in part to a citizen scientist with a passion for finding exoplanets.
No really — Wow!
We’ve already covered the story of the Wow! Signal and how we got to this point in the story, but to summarize: in 1977, a radio telescope in Ohio known as “The Big Ear” detected an unprecedented signal coming from the general direction of the constellation Sagittarius. As the fixed antenna swept the night sky thanks to the rotation of the Earth, a stream of radio noise entered the dual feed horns of the instrument, with a signal-to-noise ratio that peaked at over 30 times the typical background noise. The signal, which lasted 72 seconds, became known as the “Wow! Signal” thanks to astronomer Jerry Ehman’s excited note from the night of August 15, made in red pen on the margin of the fanfold hard copy of the data.
In the 45 years since that night, the Wow! Signal has been at the center of a storm of scientific curiosity. In some ways, it bears all the hallmarks of being a transmission from another technical civilization. The frequency of the signal was very close to the 1,420-MHz hydrogen line frequency, and anyone capable of building a radiotelescope would most likely know about that frequency and might choose to use it in their efforts to search for other life in the galaxy. The signal’s characteristics were also very much in line with what one would expect for an extraterrestrial beacon, given the rotational speed of the Earth at the latitude of the antenna. There have also been extensive efforts to provide alternative explanations for the signal, none of which have ruled out an extraterrestrial signal.
Then again, there hasn’t been much to support the Wow! SIgnal’s potential as an extraterrestrial calling card either. No other observatories working that night picked up anything similar, and multiple attempts to listen to the patch of sky for a repeat of the event have failed to hear a peep. Forty-five years on, the Wow! Signal remains the worst kind of event, scientifically speaking: a one-off, a chance observation that provides a tantalizing clue for more work, but nothing more.
Citizen Science Points the Way
And yet, scientists are still plugging away at the Wow! Signal, since it seems to be the best chance we’ve had so far to find out who might be out there. One such scientist is Alberto Caballero, an amateur astronomer from Spain who, as head of the Habitable Exoplanet Hunting project, very much has extraterrestrial life on his mind. The project enlists astronomers, both pros and amateurs, to turn their telescopes to the stars in search of faint dimming events that might result from planets passing in front of the star. The project focuses its efforts on a small group of G-type, K-type, and red dwarf stars within 100 light-years of Earth, and looks for transit signals that would be characteristic of rocky exoplanets within the habitable zone around each star.
Alberto’s interest in exoplanets took a different turn with a paper he published this year concerning a potential source for the Wow! Signal. The peer-reviewed paper suggests that out of 66 stars that were within the view of the Big Ear’s feedhorn on that night in 1977, the star 2MASS 19281982-2640123 may be a good candidate for further investigation, by virtue of its luminosity and size.
Picking up on this thread, a group of astronomers led by Karen Perez of Columbia University recently made the first coordinated, multi-telescope observations of 2MASS 19281982-2640123, with the specific intent of locating a “technosignature” from the star. Using the Green Bank Telescope in West Virginia and the SETI Institute’s Allen Telescope Array in northern California. The team coordinated observations so that both telescopes were looking at the target star at the same time, and made their observation at the same 1,420-MHz frequency of the original Wow! Signal.
Sadly, the experiment resulted in no technosignature, perhaps not a surprise since the total time that both telescopes were trained on the star was only nine minutes or so. But the effort is still significant, mainly because it’s the first time in the 45 years since the Wow! Signal was heard that a coordinated observation effort has been undertaken. Such an effort can only make it easier to coordinate observations of spurious signals, both as they pop up and after the fact. It also suggests other candidates besides 2MASS 19281982-2640123 — they found that there are actually eight Sun-like stars in the observation window used by the Big Ear that night; relaxing the criteria for luminosity, mass, and star type opens the candidate pool substantially, to over 600 stars.
There’s certainly more to come on this and other SETI efforts, and while we look forward to hearing how they turn out, for now we’re glad that a little citizen science has proven to be the foundation upon which a much broader effort has been built.
[Featured image source: North American Astrophysical Observatory.]