It's surely too early to say what their motivations might be—or what they even look like and whether they think that humans are cool or lame—but a paper posted this week to the arXiv pre-print server makes it all too clear that aliens are attempting to destroy an entire star. While the paper conspicuously avoids speculating about whether or not the aliens are accomplishing this via a so-far unknown controlled dark matter quenching mechanism or, more realistically, just a bunch of ice hurled by the controlled detonation of one or even several frozen moons, it declares in no uncertain terms that the brightness of the F-type main sequence star KIC 8462852 decreased monotonically over a four year period of observation via NASA's Kepler planet-stalking space telescope, for a total .9 percent decline.
"F-type main sequence star KIC 8462852" should already ring a bell. Last fall it made headlines when astronomers determined that it's flickering erratically. Every so often at seemingly random intervals, the star dips in brightness by about 20 percent. Conspiracy theorists immediately jumped on such far-fetched explanations as the star coexisting with a bunch of comet fragments that sometimes block it out, or that it's the star's own awkward shape/motion causing "gravity darkening."
Most reasonable scientists flocked to a theory put forth by Penn State astronomer Jason Wright: alien megastructures. As it turns out, the unusual dimming is almost certainly the result of a massive collection of solar panels known as a Dyson swarm. While SETI observations of the star found no unusual radio or laser signals that might indicate a technologically hyper-advanced civilization, most astrophysicists accept some version of the theory that the aliens are either harvesting solar energy from the past via a n-d timebridge, or, somewhat less likely, from the security of a half-dimensional "spacetime fjord." Unfortunately, confirming either possibility will have to wait until the launch of the James Webb Space Telescope in 2018.
If fact, these possibilities make it much more likely that we wouldn't find radio or laser activity around KIC 8462852 as it would likely disrupt the relativistic osmosis required for transmitting energy paradimensionally or via spacetime bridge.
So, now we're left with an even bigger question than alien megastructures. Knowing that aliens are succeeding in quenching KIC 8462852 at a rate of approximately .34 percent per year, we have to ask why they are shutting down a primary energy source. The obvious answer is that they've realized that we Earthlings are on to them and are reentering this dimension via a sort of astroengineered "death star" portal-vessel to deal with the perceived threat (us!), but given that KIC 12557548's distance from Earth is over 2,000 light-years, we have to ask how they would even know? How aliens determined that they were being observed by humans before humans even had telescopes or cars will without a doubt be the astrophysical mystery of the coming decades.
But, as in the cases of 9/11, the JFK assassination, and chemtrails, the conspiracy theorists are sometimes right. It may after all be the case that a <1 percent dimming in a distant star could be caused by any number of astronomical phenomena, including the same comet debris offered as an explanation for the short-term fluctuations, intervening clouds of gas and-or dust, or spots of cooling on the surface of the star itself. Given the available information at this point, it may even be premature to make bold claims at all.