Alien hunters detect mysterious radio signal from Proxima Centauri

Astronomers looking for signs of life beyond Earth have discovered something strange. A still unexplained radio signal appears to be coming from the direction of the star closest to the sun: a small red star about 4.2 light years away called Proxima Centauri. In addition to the excitement, at least two planets orbit this star, one of which could be temperate and rocky like Earth.

Breakthrough Listen, a decade-long search for alien broadcasts from the nearest million stars, was using Australia’s Parkes Observatory to study Proxima Centauri when the team detected the visible signal, which they named BLC-1. The radio waves were captured in observations made between April and May 2019.

“It is quite expected that from time to time you will see something strange, but this is interesting because it is a strange thing that we have to think about the next steps,” says Sofia Sheikh, a graduate student at Pennsylvania State University and the Breakthrough team member who leads signal analysis.

Although Sheikh and others strongly suspect that the signal is actually of human origin, BLC-1 is the most tempting detection Breakthrough has made so far in its search for extraterrestrial intelligence, or SETI. The team is preparing two papers describing the signal and a follow-up analysis, which is not yet complete. (Detection leaked to The Guardian before the research was ready for publication).

While researchers continue to analyze the signal, and experts caution that there is almost certainly an ordinary terrestrial explanation, even a remote hint of life beyond Earth excites people.

“There’s a lot of talk about sensationalism in SETI,” says Andrew Siemion, Principal Investigator for Breakthrough Listen. “The reason we are so excited about SETI, and why we dedicate our careers to it, is the same reason the public is so excited about it. They are aliens! Is awesome!”

Scientists have been scanning the skies for radio signals that could have an artificial origin for 60 years, beginning with Project Ozma, a search conducted in 1960 by my father, Frank Drake.

Unlike the radio waves that the cosmos produces naturally, these alien whispers are expected to closely resemble the transmissions humans use to communicate. Such signals would cover a very narrow range of radio frequencies. They would also have a characteristic “drift” indicating that the source is moving toward or away from Earth, a clue that the radio source is coming from a distant cosmic object, such as a planet orbiting a star.

“Only human technology seems to produce signals like that,” says Sheikh. “Our WiFi, our cell phone towers, our GPS, our satellite radio – all of this looks exactly like the signals we are looking for, which makes it very difficult to tell if something is coming from space or human-generated technology.”

For decades, astronomers have detected numerous candidate signals. Some turned out to come from previously unknown astronomical sources, such as pulsars, the rapidly spinning corpses of dead stars that beam radio waves into the cosmos. The first known fast radio bursts, short bursts of radio waves that are still somewhat mysterious, initially seemed as if they could be artificial signals. The signals called perytons, which are less energetic bursts of radio emission, were also surprising until scientists determined their origin: a microwave oven.

The BLC-1 could be emitting from a satellite that has not yet been identified, an aircraft traveling overhead, a transmitter on the ground near the telescope’s line of sight, or perhaps something even more mundane, like faulty electronics in a nearby building or a passing car.

“All of our SETI experiments are carried out in an absolute sea of ​​interference. There are tons of signals, ”says Siemion. “It’s about being able to differentiate between a very distant technology firm and our own technology.”

And then there are the signals that astronomers have not been able to definitively identify to a natural source, like the famous “WOW!” A signal picked up by the Ohio State University Radio Observatory, colloquially known as Big Ear, in 1977. This extremely bright barrage of radio waves initially looked like a real SETI detection, but no one has been able to verify or find it again.

In 2015, Breakthrough Listen launched a decade-long search funded by Silicon Valley investor Yuri Milner, and so far, the team has found nothing definitive in their explorations of the skies.

Beginning in April 2019, Breakthrough pointed the Parkes telescope at Proxima Centauri, not necessarily because scientists were looking for aliens, but because they hoped to better understand the gigantic flares that small red dwarf stars like Proxima frequently emit. While processing those observations this summer, Shane Smith, a Hillsdale College student in Michigan who works with Breakthrough, saw BLC-1 seemingly radiating from the star.

Although the signal is weak, the BLC-1 passed all the tests the Breakthrough team uses to filter out the millions of signals generated by humans: it was narrow in bandwidth, seemed to vary in frequency, and disappeared when the telescope looked away. by Proxima. to a different object. In the following days four similar signals appeared, although some have been ruled out as radio interference.

“Our algorithm is very optimistic about what alien technology could be,” says Sheikh. “But this is very exciting because we have never reached the stage where the algorithm found something really interesting.”

If BLC-1 is, against all odds, a postcard of the star system next door, then statistically speaking, the Milky Way must absolutely be full of communicating civilizations, says Seth Shostak of the SETI Institute. “In this case, there would be more than half a billion societies in our own galaxy, that sounds like a lot.”

Since the detection, the team has re-observed Proxima Centauri and found nothing. Groundbreaking scientists have also examined the signal itself and determined that its drift in frequency does not match the drift expected of a planet orbiting the star. But they also failed to pin the transmission on any satellite orbiting Earth, an investigation Sheikh says is ongoing. The team is working on developing new tests that could identify the origin of the signal, including continuing to point the Parkes telescope at Proxima.

“If you want to make scientific statements, you will have to be able to re-observe and replicate the phenomenon,” says Sheikh. “This is how the scientific method works.”

Earlier this year, Jill Tarter from the SETI Institute told me that the process of creating new tests and working diligently to confirm the origin of a signal is a natural part of the SETI effort, and one that everyone can learn from and benefit from.

“We’re looking for something else out there, someone else out there,” Tarter said at the time. “Suddenly seeing interference and thinking that it might be what we’re looking for, and then figuring out what we have to do to be able to discriminate and have confidence in whatever result we can get, that’s a good lesson.

Siemion already says that evaluating BLC-1 has taught the team a lot about how to test their data. Follow-up observations of Proxima Centauri will be valuable in understanding how those stars behave, as well as in achieving a full SETI search of a nearby star system with known planets, even if it is not populated by technologically savvy aliens.

Ultimately, I think we will be able to convince ourselves that [BLC-1] it’s interference, ”says Siemion. “But the end result will undoubtedly make our experiments more powerful in the future.”