Tuesday, January 24, 2017

"Megastructure Star" Ate a Planet

Nope, not comets!

In 2015, scientists working with the Kepler Space Telescope announced that they had discovered something strange about a star called KIC 8462852. According to their observations, the star's light pattern was very strange, and appeared as if a large amount of matter was orbiting very close to the star, causing it to dim over time.

At first, it appeared to be a planetary accretion disk, except that the star appeared to be far too old to still have one. Then, the idea was floated that perhaps the light could be obscured by some sort of alien megastructure, which was reported by just about every media outlet. Over time, the consensus settled on a large collection of cometary fragments orbiting the star closely, though the question why the comets were positioned so strangely still prompted questions.

But earlier this month, scientists announced that they may have come up with a possible explanation. It's not aliens, but it's awe-inspiring nonetheless - they believe that KIC 8462852 "swallowed" a planet.

Planets don’t usually fall into their stars, but one could if, say, a large body like a comet knocked the planet out of its orbit and sent it to its doom. They reason that when a star swallows something as large as a planet, for a cosmologically short period, between 200 years and 10,000 years, its brightness increases as it burns away the planet’s matter. Then it would decline again. So if we happen to have started watching the star towards the end of such a period, it might explain the 14% fall in brightness over 100 years.

Also, an eaten-up planet could leave behind large debris, such as its moon or large pieces of the planet that for some reason weren’t sucked in. These large bodies could be passing in front of the star in orbit, blocking some of its light and causing the brief dips seen by the Kepler space telescope.

As with all the other explanations about KIC 8462852, this is still just a hypothesis. However, if KIC 8462852 is indeed gobbling up planets, some other stars must do it too. Finding another one would be one way to throw away the alien-megastructure hypothesis. (Unless, of course, the other star also just happens to have a Dyson sphere being built around it.)

Jason Wright of Pennsylvania State University at University Park, who suggested the alien-megastructure hypothesis, believes that the planet-gobbling explanation from Metzger and his colleagues is a strong one. “This paper puts a merger scenario on the table in a credible way,” he told the New Scientist. “I think this moves it into the top tier of explanations.”


Modern astronomy has shown us that the universe is a violent place in which galaxies collide, stars explode, and apparently planets fall into their stars. Fortunately for us, this most likely requires a collision with another heavenly body, and we don't seem to be due for anything like that here in the solar system. But as the present condition of Earth appears to be the aftermath of just such a planetary collision, it would seem that our world was pretty lucky avoid falling into the Sun after that cataclysmic event.

So the other takeaway is that we still haven't found aliens, though if they are out there and close by, relatively speaking, I imagine that it is only a matter of time. We are constantly getting better at identifying planets orbiting distant stars, and new, more advanced measuring instruments are on the way.

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