'Alien Signal' was Most Likely a Cosmic Miscommunication
September 15, 2016
There are hundreds of billions of stars in the Milky Way galaxy. There are more than one septillion (the number one followed by 24 zeroes) stars in the observable universe.
Scientists have already found several planets that are roughly Earth-sized and the right distance away from their stars to support life, similar to the kind we have on Earth. Around those septillion stars, there could be, many scientists believe, planets with intelligent life.
Groups of researchers around the world are dedicated to searching for that life and in late August, scientists from the Search for Extra Terrestrial Intelligence (SETI) Institute investigated evidence suggesting they might have found it. A radio signal was discovered that appeared to have come from a planet light years away. While the signal turned out to be an errant signal made by humans here on Earth most likely, the investigation itself revealed plenty of interesting scientific information.
The story starts at a radio telescope in the southwestern tip of Russia, which is typically used to look at the radio waves produced by stars and planets. In May 2015, however, the telescope picked up an abnormal, weak signal. The signal registered at 0.75 Janskys—a measurement of how much radiation is contained within an electromagnetic signal. At the same frequency, the Milky Way gives off 20,000 Janskys as we see it from Earth, so the detected signal is subtle.
Tracing backwards, the signal appeared to have come from a star system called HD 164595, which is about 90 light years from Earth. The central star is a few billion years older than our sun, but roughly the same size and it has one Neptune-sized planet that we can see from Earth.
More than a year later in August 2016, the researchers working in Russia alerted SETI about the signal. True to SETI’s protocol for these types of events—there is a nine-step program for verifying potentially alien signals as alien—scientists at other radio telescopes were notified, and began searching for the signal again to figure out what it was and where it came from.
Starting on August 29, SETI began sweeping the area of the sky around HD 164595 with their own telescope array: a field full of satellite dishes outside San Francisco called the Allen Telescope Array. For two days, the search never yielded a signal stronger than 0.1 Janskys.
All the while, Seth Shostak, a senior astronomer for SETI and colleagues were making calculations about the properties of a signal that could reach from HD 164595 to Earth. Even through the near-emptiness of space, radio signals, which are just beams of light, diffuse and lose their strength. If an alien civilization from HD 164595 were trying to directly contact Earth by sending one signal in Earth’s direction, they would need to use roughly a trillion watts, which by comparison is roughly the entire power consumption of humankind.
The problem with that picture is how these hypothetical alien beings would even know we are here. We humans have not been broadcasting TV or radar signals for the 90 years it would take them to reach HD 164595. It would, therefore be unlikely that anyone out at HD 164595 would have any way to know humans were here on Earth.
More likely, this hypothetical alien race would have been broadcasting out in every direction if they were trying to reach other civilizations. The power required to generate that type of signal is hundreds of times greater than the energy that the Sun transmits to Earth. All the light, heat, power to grow plants and cause sunburns on Earth multiplied hundreds of times for one shot in the dark message. Needless to say, that’s well beyond the power we are capable of developing, and possibly beyond the capability of another civilization, especially when the HD 164595 star—where a civilization there would get most of its energy—is about the same size and produces as much energy as our sun.
Meanwhile, researching the original signal revealed a different origin, while the radio telescopes were searching for more signals in the skies. The Russian Academy of Sciences put out a press release that the signal most likely had “terrestrial origin,” meaning it came from home. Alexander Sipatov, Director of the Institute of Applied Astronomy at the Russian Academy of Sciences remarked in an article for the Russian news agency that back in the days of the Soviet Union, he and other astronomers at these telescopes picked up similar signals, which they traced back to Soviet military satellites.
Given the lack of evidence of a repeat signal, how much power it would theoretically require to make that signal and the past history of false alarms by Soviet satellites, the alien signal was most likely no more than an errant butt-dial from a satellite. It would certainly not be the first false alarm. In the late 1990s, Australian researchers detected short signals they called “perytons” that they initially thought came from beyond the Milky Way. It took them 17 years to determine that these perytons were coming from hungry scientists opening the microwave before their Hot Pockets were done cooking.
All these long odds and misidentifications may make it seem like the search for extraterrestrial life is somewhat futile. Still, with all the stars and planets in the universe, there are plenty of places to look for life and scientists will continue to scan the stars for any sign of it.
Daniel Lane covers science, medicine, engineering and the environment in North Carolina.