Are we alone in the Galaxy? Is there life in other planets? Have other species evolved to technological societies comparable to ours? Or maybe the right question is, How near are we from detecting signals of alien life?
In 2013 I met Lisa Kaltenegger at The Falling Walls event, in Berlin. She is an astronomer working now at Cornell University, looking for signatures of life in exoplanets (planets outside our solar system). She is quite convinced that we are very near to detecting them.
But last week, an article was published pointing to a star, KIC 8462852, whose light shows weird changes in luminosity. Astronomers can't explain it and, of course, some raise the question, Why not? to the possibility that the behavior is due to an alien technology.
Changes in luminosity is a well known effect in stars, some of them are called variable stars. It can be produced by the star's internal dynamics, spots in its surface, by the transit of one or various planets in front of the star, hiding a small portion of the star. This last effect is used to detect planets around stars, but it lowers, at much, about 1% of its total luminosity. Another method to detect exoplanets is by tracking the gravitational effect of the planet in its star (a small but detectable bouncing effect). For this star those reductions arrive up to an inexplicable 20%. Astronomers have checked all the known physics on luminosity variability in stars, and haven't been able to explain the observations of KIC 8462852. They have also accounted for different errors in their instruments, as well as for the effect of interstellar dust, but haven't found an acceptable explanation.
Are those irregular, unpredictable and inexplicable decreases in luminosity due to a technological structure being built near the star to get its energy to feed an alien society in a nearby planet? If that was the case we would be facing a much more advanced civilization, one that can use and control the energy of its star for its needs. This idea is not new, in fact it can be found in science fiction stories. Fred Hoyle, British astronomer that coined the term "Big Bang" Theory, wrote a novel, The Black Cloud, on something similar. Some scientists say that a civilization that can control its star energy is a type II civilization. If it can control its planet energy it is a type I civilization, and if it can control its galaxy energy it is a type III civilization. We are somewhere around type 0.8 civilization.
But this is not the kind of alien life that Dr. Kaltenegger is expecting to find in the next decades. What she and many other astronomers are studying are signals from the atmosphere of planets. The light that travels through the planet's atmosphere, is absorbed and re-emitted. This changes its properties (frequency distribution, for instance) and can give hints to astronomers about the atmosphere's content. Depending on the content, we can know it can have been produced without the help of organic life (bacteria, plants, ...).
A similar announcement took place in the 1960s, when astronomers detected a very precise periodic signal coming from a star. It was originally coined LGM, after Little Green Men. But that happened to be the discovery of a new type of stars, a pulsar or pulsating star, a star of very high density and magnetic field, that ejects powerful X rays in an specific axes. As the star is rotating and that X ray doesn't need to be in the same axes as the axes of rotation of the star, when the ray points to the Earth we detect is as a pulse, that is repeated every time the star rotates. The speed of rotation can be very high, several times per second.
If KIC 8462852 is the home of a technological alien society or new physics to understand we will know in the near future. In any case, astronomy doesn't stop being surprising and fascinating.
Physicist, working in quantum optics and nonlinear dynamics in optical systems. Loves to communicate science.