I try to keep my rational brain engaged, but man, sometimes it's hard going.
Like when I read the story that popped up over at Scientific American last Friday. My ears perked up at the very first line: "It's never aliens, until it is."
Written by Jonathan O'Callaghan and Lee Billings, it tells about a recent discovery made by "Breakthrough Listen," the search-for-extraterrestrial-intelligence program launched by entrepreneur Yuri Milner in 2015. Despite scanning the skies for five years looking for something that might be a sign of alien intelligence, Breakthrough Listen hasn't found anything that couldn't be explained using ordinary astrophysics...
... until now.
Maybe. I hate to add that word, but... "rational brain engaged," and all. There's a lot that's exciting about what they discovered, not least that the signal they found comes from Proxima Centauri -- the nearest star to the Sun, right in our own neighborhood at only 4.2 light years' distance. (Okay, I probably shouldn't say "only." 4.2 light years is about 25,000,000,000,000 miles. One of the fastest spacecraft ever made by humans, Voyager 2, would still take 73,000 years to reach Proxima Centauri -- if it were heading that way, which it's not.)
The proximity of the signal's source is hardly the only exciting thing about it. After all, the universe has plenty of radio sources, and all the ones we've found so far have purely prosaic explanations. The signal is weirdly compressed, occupying a narrow band of frequencies centering around 982 megahertz. Interestingly, this is a frequency range that is usually fairly empty of transmissions, which is one of the reasons the signal stood out, and decreases the likelihood that it's some kind of human-made source being picked up accidentally. "We don’t know of any natural way to compress electromagnetic energy into a single bin in frequency,” said astrophysicist Andrew Siemion, who is on the team that analyzed the signal. "Perhaps, some as-yet-unknown exotic quirk of plasma physics could be a natural explanation for the tantalizingly concentrated radio waves, but for the moment, the only source that we know of is technological."
The "tantalizing" part is that we know for sure that Proxima Centauri has at least one Earth-like planet -- Proxima b, which is 1.2 times the size of the Earth, and orbits its star in eleven days. (If that doesn't sound very Earth-like, remember that Proxima Centauri, as a red dwarf, is a lot less massive than the Sun, so its "Goldilocks zone" -- the band of orbital distances that are "just right" for the temperatures to allow liquid water" -- is a lot closer in, and the planets in that region travel a lot faster.) Red dwarf stars are prone to solar flares, so some of the more pessimistic astrophysicists have suggested that the radiation flux and general turbulence would destroy any nearby planets' atmosphere, or at least shower the surface with sufficient ionizing radiation to prevent the development of complex biochemistry, let alone life.
But it's important to realize that this, too, is a surmise. Truthfully, we don't know what's down there on Proxima b -- just that it's got a rocky surface and a temperature range that would allow for liquid oceans, rivers, and lakes.
Just like here.
In short, finding a suspicious radio signal from the nearest star to our own is pretty amazing, even if I *wince* *grimace* keep my rational brain engaged.
The fact is, even the scientists -- normally the most cautious of individuals -- are sounding impressed by this. "It’s the most exciting signal that we’ve found in the Breakthrough Listen project, because we haven’t had a signal jump through this many of our filters before," said Sofia Sheikh of Pennsylvania State University, who led the team that analyzed the signal and is the lead author on an paper describing it, scheduled for publication this spring.