Big Ear Radio Observatory and North American Astrophysical Observatory (NAAPO)
A color scan of the original computer printout of the "Wow!" signal as detected by the Big Ear Radio Observatory in 1977.
Nov. 8, 2011 --
Despite the occasional report of an extraterrestrial sighting, be it through a microscope revealing curious shapes in a meteorite or a photo of wispy lights taken at the blurry end of a camera lens, aliens have yet to make contact with humans. Even the White House yesterday put out a statement declaring that the federal government "has no evidence that any life exists outside our planet, or that an extraterrestrial presence has contacted or engaged any member of the human race." Humans may not yet have encountered life outside of our planet, but many scientists see it as an inevitability. In 1960, astronomer Frank Drake came up with the now eponymous equation which provided an estimate of the number of civilizations in our galaxy. Although scientists continue to debate the application of his formula as well as alternatives, Drake's own solution to the equation is 10,000 civilizations, suggesting intelligent, technologically advanced life outside our planet is common. How these different civilizations, including our own, find each other is an important question for anyone here on Earth looking for extraterrestrials. Explore how aliens might stumble upon our planet -- and how we might actually spot them first.
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Before we can began to search the skies, we have to start by narrowing down our options. Sticking within our own galaxy is a good start, since we're more likely to spot a neighbor closer to us than one further away. Astronomers may also elect to focus their attention on stars closer to the center of the Milky Way, where 90 percent of its stars are clustered. Furthermore, the stars here are a billion times older than the sun, giving life more time to develop biologically and technologically. Many stars are unsuitable for nurturing life, and even stars that do have the appropriate "spectral type" may host exoplanets inhospitable to life due to their location relative to their parent star, size or composition. These criteria would not only help us find aliens, but also help them find us. After all, Earth would stand out as a hospitable planet, according to a paper published in 2007 in Astrophysical Journal.
If aliens are looking for us, they're scanning the same, vast, dark and mostly empty expanse of space that we are. It's a good thing then that we're leaving the lights on to make it easier to find us. According to Abraham Loeb, of Harvard University and Edwin Turner, from Princeton University, by scanning the skies for artificial illumination as opposed to naturally occurring light sources, both human and extraterrestrial astronomers might be able to find signs of life. Existing telescopes would be able to see a city the size of Tokyo as far as the edges of our solar system.
BLOG: CITY LIGHTS COULD REVEAL ET
For more than 25 years, the SETI Institute has been scouring the skies for signs of alien life. However, long before the institute was established, scientists have tried to catch a communication signal from another world. Scientists looking for alien signals use a combination of optical and radio telescopes, such as the one seen here. Dropping in on a signal without knowing the source of the communication is the tricky part, however, and researchers narrow down their search by targeting specific kinds of stars. With their citizen science program, SETI@home, the institute has enlisted three million additional observers analyzing data for traces of an alien signal.
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Have aliens already stopped by for a visit, even though we weren't at the door to meet them? If they have, shouldn't they have left something behind? An artificial object of alien origin could be lurking in our solar system without our knowledge. As Discovery News' Ray Villard explains: "In a paper published in the 1960s, Carl Sagan, using the Drake Equation, statistically estimated that Earth might be visited every few tens of thousands of years by an extraterrestrial civilization." Further out beyond our solar system, aliens may have left what essentially amount to interstellar billboards large enough to be seen by, say, a planet-hunting telescope like Kepler. These last two scenarios, of course, envision an extremely technologically advanced civilization well beyond the engineering capabilities of humankind. At the same time, humans have sent spacecraft beyond the solar system, including Pioneer 10 and 11 as well as Voyager 1 and 2. All of these spacecraft are equipped with what are essentially calling cards for the human race -- small plaques in the case of the Pioneer spacecraft and golden records for the Voyager spacecraft (seen here).
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Humans may rely primarily on fossil fuels as their primary means of energy, but that doesn't mean extraterrestrials in a far off civilization have the same power source. Solar power could be one option, though not quite with the same black panels we use on Earth. A super civilization could even tap into a black hole to meet its energy needs. If aliens are tapping to these cosmic bodies, that should make them all the more detectable from Earth. How would we know whether an alien race was relying on a black hole as a source of energy? As Discovery News' Ray Villard explains: "Tell-tale evidence would come from measurements that showed the black hole weighed less than 3.5 solar masses. That's the minimum mass for crushing matter into a black hole via a supernova core-collapse."
In one of the most unusual -- and highly unlikely -- first-contact scenarios, aliens would be able to recognize us by the level of greenhouse gas emissions we pump into our atmosphere. Not only that, according to a hypothesis put forward by researchers affiliated with NASA and Pennsylvania State University (though not directly tied with either institution), but aliens may use that as cause to wipe out the human race. In this bizarre set of circumstance, aliens view human advancement as a destructive force spiraling out of control. To avoid the threat of a future adversary, extraterrestrials clear out the competition.
BLOG: TO SAVE THE GALAXY, DESTROY HUMANITY
The story behind the famous “Wow!” signal has an eerie quality that has inspired countless science fiction alien encounters and is often lauded as one of the strongest pieces of evidence that we are, in fact, not alone in the universe.
However, its “alien intelligence” authenticity has been questioned since that fabled night on Aug. 15, 1977 at 10:16 p.m. ET when astronomer Jerry Ehman used the Ohio State University’s Big Ear radio telescope to sweep the skies for signals that may have originated from an extraterrestrial civilization.
On that night, Ehman found something. And since that night, astronomers have been trying to figure out what it means.
While pointed in the direction of 3 star systems named Chi Sagittarii, in the constellation of Sagittarius, Big Ear detected a 72 second radio wave burst, a signal far stronger than background noise. On the observatory’s computer printout, Ehman circled the burst with the infamous annotation “Wow!”
This excitement wasn’t an overstatement, it was this kind of signal he was looking for, the kind of signal astronomers thought a technologically-capable alien civilization would produce.
The Big Ear printout contains a bunch of apparently random numbers and letters, but Ehman’s red pen circles a cluster of digits “6EQUJ5" with other circles around a "6" and "7" on separate columns. This particular code first uses the numbers 1-9 and then the alphabet A-Z to denote signal strength. As the burst suggests, the signal strength hit “6" and then blasted through the letters reaching a peak of “U” before subsiding back into the numerical scale at "5." There was then a slight wave trailing the main signal (hence the circled “6″ and “7″). The wave profile of the “Wow!” signal is graphically envisaged here.
However, since that day in 1977, a detection of a signal of that strength has not been replicated. Even after the SETI Institute was founded in 1984, and countless efforts have been made to find another radio burst like the “Wow!” signal, astronomers have been faced with silence in the cosmos; a problem that has only served to intensify the Fermi Paradox unease.
Now, Antonio Paris of St Petersburg College, Fla., an ex-analyst of the US Department of Defense, hopes to solve the mystery and he suspects that an entirely different cosmic phenomenon is to blame.
In an interview with TheGuardian.com, Paris says that his investigative background sent him on a mission to find another possible explanation for the “Wow!” signal and he tracked down two “suspicious” comets that may have been in the vicinity of Chi Sagittarii on Aug. 15, 1977. Interestingly, these comets, called 266P/Christensen and 335P/Gibbs, were only discovered in 2006 and 2008, so weren’t considered as possible reasons for the signal in 1977 as no one knew of their existence.
But what have comets got to do with errant radio bursts?
The “Wow!” signal was recorded in the 1420MHz radio frequency band. It just so happens that cosmic neutral hydrogen naturally radiates at this frequency -- it is therefore an abundant signal that is commonly used in astronomy. This is no coincidence; through alien-hunting logic, should there be an extraterrestrial species wanting to make contact, what frequency would they use? Firstly, as we only have ourselves to use as an alien template, we have to assume that hypothetical aliens will likely use radio waves. Secondly, if they are using radio waves to communicate with us, they would likely use a frequency that other intelligent aliens would be naturally tuned into. 1420MHz is the “universal water cooler,” where intelligent life could check into and potentially chat.
The bummer is, however, that comets contain copious amounts of hydrogen in their atmospheres. Say if the “Wow!” signal was actually caused by the chance passage of a comet through the radio telescope’s field of view, packing a powerful radio surge?
In 2017, Comet 266P will once again orbit in front of Chi Sagittarii and Comet 335P will do so the following year and Paris wants to test this hypothesis. Unfortunately, existing radio telescopes are already booked, so he has to buy or build his own radio antennae in time for the cosmic encounters. He has a crowdfunding campaign set up to raise the $20,000 he needs and is most of the way there.
It may be a long shot, but as is the way with many astronomical studies, all possible phenomena need to be ruled out before a discovery is made and, should Paris’ experiment prove the “Wow!” signal was in fact caused by interference by an undiscovered comet, the universe will get quieter once again, making the Fermi Paradox even more bewildering.