The Truth about “Alien Megastructures” surrounding Tabby’s Star
Tabby’s Star made a lot of headlines back when it was announced in 2015. Astronomers found some weird features about the star which baffled them entirely. One of the many plausible explanations that seemed to fit was the presence of alien megastructures that harvested the star’s energy.
Back in 2015, Atlantic first reported that astronomers have discovered a new star in the Milky Way. It was quite far from the earth. It was in the Cygnus constellation, that is almost 1300 light years away from the Earth. The star itself was quite an ordinary one. However, every now and then, the brightness of the star would drop.
This technique has often been used by astronomers to find planet systems in the universe. If a star has a lot of planets, chances are that the planet will pass between the star and the observer, and in this case, astronomers on the Earth. The passing planet would eclipse the star momentarily, causing a dip in the brightness. Terrestrial telescopes have used this technique to detect a lot of exoplanets.
From these fluctuations of the star, a lot can be learnt about the nature of the planets that surround the star. This includes the size, the composition and so on. In case of planets, the dip in light would also indicate the period of revolution. This, in turn, would help the astronomers to find out how far planet it, as well as its mass. But if it is a planet, the dimming should be periodic in nature, that means, the duration of time between each dim would be fixed. For multiple planets, it should have a certain pattern. This star exhibited none of those properties.
What is strange is that the size of planets is quite small compared to that of stars. So, anyone observing our solar system from the outside will see a 1% drop in the brightness when Jupiter eclipses the sun. A planet that is as large as Jupiter only reduces the sun’s brightness by only 1%. This star, on the other hand, had a brightness drop of 20% and these brightness drops occurred randomly.
This means something massive was blocking the light from the star.
Initially, astronomers proposed multiple natural theories, such as passing comets. But none of them seems to fit the bill perfectly. So, they started considering something else. It was an exciting explanation, one that hearkened to a kind of technology imagined by the science-fiction writer Olaf Stapledon, and later popularized by the physicist Freeman Dyson, that would allow intelligent extraterrestrial life to harness the energy of their star.
An advanced alien civilization would have a large energy requirement that they would harvest from the star. They could build themselves a structure vast enough to surround its entire solar system including the planets in the solar system. The structure would collect the energy from the star and make them usable to the alien civilization.
Until October 2017, this idea was on the table. However, the mysterious flickering around the star in the swan constellation is likely caused by ordinary dust, according to an analysis of new data published in The Astrophysical Journal Letters.
This data comes from the analysis of the nature of the light of the star. It has been found that the dimming occurred more across the blue wavelengths and not so much in the red wavelengths. This indicates whatever is surrounding the star is allowing more red light to pass through than blue light. The most fitting suspect here is dust. Dust in the atmosphere is the same reason why the sky turns reddish during sunset. A cloud of cosmic dust in which each of the particles are less than a micron across is surrounding the star, making it dim so much.
“If you imagine you have some light source and a planet—which is an opaque object—goes in front of it, it will block blue light just as much as it would the red light,” said Tabetha Boyajian, an astronomer at Louisiana State University who led the analysis. “What we’re seeing for this star is that the drop in the star’s brightness is much greater in the blue than it is in the red.”
If the dimming occurred equally across all wavelengths, then alien megastructure (or at least something opaque) would have been on the table. But that is not the case here. Searches for radio signals coming from the star have also turned up empty, providing another blow to the alien theory.
However, the dust could theory does not give a complete explanation either.
Observers expected to see an excess of infrared lighting radiating from the star, but the did not find any. So, as of now, what truly surrounds the star is still a mystery. However, the alien megastructures theory is off the table.