It is one of the greatest astronomical mysteries of the moment.
Since 2011, the so-called Tabby star has registered irregular changes in its brightness that cannot be explained by the passage of a planet , which is what usually alters the brightness of the stars. These disturbances are variable and create different light curves, so a priori they could not be caused by the planet passing in front of Tabby.
Because of this, the origin of these disturbances has scientists baffled. So much so that all kinds of hypotheses have circulated about it.
The most famous of them maintains that it is an alien structure, an artificial device designed to remain suspended in the universe: a Dyson sphere (in honor of the designer of the hypothesis); that it could be harvesting energy from the star to fuel an advanced alien civilization, thereby reducing its brightness.
However, astronomers favor an explanation that is simpler and less typical of a science fiction movie.
The latest analysis that has been carried out regarding Tabby’s strange behavior once again refutes the alien hypothesis. NASA scientists have concluded that the strange structure that appears to surround Tabby is probably simply an uneven dust cloud moving around the star.
The study was based on NASA’s Spitzer and Swift missions and the Belgian AstroLAB IRIS observatory.
According to a NASA statement, the explanation is as follows: the researchers found less obscuration in the star’s infrared light than in its ultraviolet light . This effect can only be produced by dust particles, since any larger object would obscure all wavelengths equally.
To understand it better, let’s move it into everyday life: if you go to the beach on a sunny day and sit under the umbrella, it reduces the amount of sunlight that hits your eyes at all wavelengths. But if you wait for the sunset, it will look red, because blue and ultraviolet light is scattered through small dust particles.
The new study suggests that the objects causing Tabby’s star’s long-term dimming cannot be more than a few micrometers in diameter.
I mean, they are dust.
A hypothesis that ends with the idea of the extraterrestrial mega-structure and other more exotic speculations.
Tabby’s strange behavior
NASA’s Kepler Space Telescope has been observing irregular dimming in the star for years that, as we have seen, cannot be explained by a planet passing in front of it. Kepler even detected a blackout of up to 20% in a matter of days . The star has shown other slight shifts of brightness with no clear periodicity and no plausible explanation.
Its origin is, to say the least, enigmatic.
The bottom line is that none of these behaviors is expected for stars more massive than the Sun , nor has it ever been observed in any of them.
Another possible explanation
This same year, a team of Spanish researchers, from the University of Valencia and the Institute of Physics of Cantabria, elaborated another possible explanation, something more complex but equally plausible.
Although in principle it was ruled out that these changes in brightness were produced by the passage of a planet, due to their irregular curves, the Spanish team determined that the changes would not only be produced by a massive planet, but also that it would have rings , and would be accompanied, as it passed, by two groups of asteroids.
A detailed observation will be needed to test such a hypothesis, which can be done in 2023, the next time Tabby passes, theoretically, this supposed planetary group.
In either case, the alien hypothesis loses steam . However, there is no evidence yet and therefore no hypothesis can be ruled out.
Image: illustration representing a hypothetical uneven ring of dust orbiting Tabby./JPL-Caltech/NASA.
References: Huan YA Meng, George Rieke, Franky Dubois, Grant Kennedy, Massimo Marengo, Michael Siegel, Kate Su, Nicolas Trueba, Mark Wyatt. ‘Extinction and the Dimming of KIC 8462852’. (2017). The American Astronomical Society. Doi.org/10.3847/1538-4357/aa899c
