Detecting Signs of Aliens

Detecting Signs of Aliens

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From time to time, the news media falls in love with stories about how aliens have been found. From the detection of a possible signal from a distant civilization to tales of an alien megastructure around a star observed by the Kepler Space Telescope to the story of the WOW! signal detected in 1977 by an astronomer at Ohio State University, any time there's a hint of a puzzling discovery in astronomy, we see breathless headlines that aliens have been found. In point of fact, there hasn't been an alien civilization found… yet. But, astronomers keep looking!

Finding Something Weird

In late summer 2016, astronomers picked up what seemed like a signal from a distant sun-like star called HD 164595. Preliminary searches using the Allen Telescope Array in California showed that the signal picked up by a Russian telescope was not likely from an alien civilization. However, more telescopes will check out the signal to understand what it is and what could be making it. For now, however, it's problem not little green aliens sending us a "howdy".

Another star, called KIC 8462852, was observed by Kepler for more than four years. It appears to have a variability in its brightness. That is, the light we perceive coming from this F-type star dims periodically. It's not a regular period of time, so it's probably not caused by an orbiting planet. Such planet-caused dimmings are called "transits". Kepler has cataloged many stars using the transit method and found thousands of planets this way.

But, the dimming of KIC 8462852 was just too irregular. While astronomers and observers worked on cataloging its dimmings, they also talked to an astronomer who had been thinking hard about what we might see if a distant star had planets with life on them. And, in particular, if that life was technologically able to build superstructures around their star to harvest its light (for example).

What Could it Be?

If a big structure orbited a star, it could cause the variability in the star's brightness to be irregular or even random-seeming. Of course, there are some caveats with this idea. First, distance is a problem. Even a fairly large structure would be difficult to detect from Earth, even with very strong detectors. Second, the star itself could have some strange variable pattern, and astronomers would need to observe it for longer periods of time to figure out what it is. Third, stars with dust clouds around them can also have fairly large planetary structures forming. Those planetesimals could also cause irregular brightness "dips" in the starlight we detect from Earth, especially if they were orbiting at staggered distances. Finally, catastrophic collisions between clumps of material around a star could deliver huge groups of objects such as cometary nuclei in orbit around the star. Those could also affected the perceived brightness of the star.

The Simple Truth

In science, there's a rule that we follow called "Occam's Razor" - it means, essentially, for any given event or object you observe, generally the most plausible explanation is the simplest one. In this case, stars with clumps of dust, planetesimals, or roving exo-comets are more likely than aliens. That's because stars FORM in cloud of gas and dust, and younger stars still have material around them left over from the formation of their planets. KIC 8462852 could be in in a planet-forming stage, consistent with its age and mass (it's about 1.4 times the mass of the Sun and a bit younger than our star). So, the simplest explanation here is NOT an alien megacomplex, but swarms of comets.

The Search Protocol

The search for extrasolar planets has always been a prelude to a search for life elsewhere in the universe. Each star and planet system discovered to have worlds has to be examined carefully so that astronomers understand its inventory of planets, moons, rings, asteroids, and comets. Once that's done, the next step is to figure out if the worlds are friendly to life -- that is, are they habitable? They do this by trying to understand if the world has an atmosphere, where it is in its orbit around the star, and what its evolutionary state might be. So far, none have been found hospitable. But, they'll be found.

Odds are, there is intelligent life elsewere in the universe. Eventually, we will detect it - or it will find us. In the meantime, astronomers on Earth continue to search for habitable planets around likely stars. The more they study, they more they'll be ready to recognize life's effects elsewhere.