It's been a couple of years since I've last heard something about the SETI project but now they're back in the news due to the discovery of a mysterious signal. Astronomers using the RATAN-600 radio telescope in Zelenchukskaya, Russia found a strong signal in the direction of HD164595, a sun-like star about 95 light years from our planet.
The HD164595 system has at least one planet, which is similar in size to Neptune and believed to be unattractive for life, but it may have other planets as well. Scientists observed a significant signal at the 11GHz band, which is highly unlikely to be generated by known astronomical sources.
While the signal is deemed worthy of further study, SETI writes the chance of this being a signal from aliens is low, but they've swung the Allen Telescope Array (ATA) in the direction of HD164595 in hopes of picking up the signal.
SETI calculated the energy required to broadcast such a signal to Earth, and explains that even if extraterrestrials are pointing it directly at Earth, it would require roughly the same amount of power as what's consumed by all of humankind combined:
Now note that we can work backwards from the strength of the received signal to calculate how powerful an alien transmitter anywhere near HD 164595 would have to be. There are two interesting cases:
(1) They decide to broadcast in all directions. Then the required power is 1020 watts, or 100 billion billion watts. That’s hundreds of times more energy than all the sunlight falling on Earth, and would obviously require power sources far beyond any we have.
(2) They aim their transmission at us. This will reduce the power requirement, but even if they are using an antenna the size of the 1000-foot Arecibo instrument, they would still need to wield more than a trillion watts, which is comparable to the total energy consumption of all humankind.
Both scenarios require an effort far, far beyond what we ourselves could do, and it’s hard to understand why anyone would want to target our solar system with a strong signal. This star system is so far away they won’t have yet picked up any TV or radar that would tell them that we’re here.
We should learn more in the coming days/weeks, but odds are high this signal is of a terrestrial origin. ARS Technica got in touch with Nick Suntzeff, a Texas A&M University astronomer, and heard it could be a military broadcast:
Suntzeff added that he would not be surprised if the signal was due to a terrestrial origin, because it was observed in part of the radio spectrum used by the military. "God knows who or what broadcasts at 11Ghz, and it would not be out of the question that some sort of bursting communication is done between ground stations and satellites," he said. "I would follow it if I were the astronomers, but I would also not hype the fact that it may be at SETI signal given the significant chance it could be something military."