Astronomers say comet fragments best explanation of mysterious dimming star

November 25, 2015, Iowa State University
This illustration shows a star behind a shattered comet. Observations of the star KIC 8462852 by NASA's Kepler and Spitzer space telescopes suggest that its unusual light signals are likely from dusty comet fragments, which blocked the light of the star as they passed in front of it in 2011 and 2013. The comets are thought to be traveling around the star in a very long, eccentric orbit. Larger image. Credit: NASA/JPL-Caltech

Was it a catastrophic collision in the star's asteroid belt? A giant impact that disrupted a nearby planet? A dusty cloud of rock and debris? A family of comets breaking apart? Or was it alien megastructures built to harvest the star's energy?

Just what caused the mysterious dimming of star KIC 8462852?

Massimo Marengo, an Iowa State University associate professor of physics and astronomy, wondered when he saw all the buzz about the mysterious star found by citizen scientists on the Planet Hunters website.

Those citizen scientists were highlighting measurements of recorded by NASA's Kepler spacecraft. Tiny dips in a star's brightness can indicate a planet is passing in front of the star. That's how Kepler astronomers – and citizen scientists using the internet to help analyze the light curves of stars – are looking for planets.

But this star had deep dips in brightness – up to 22 percent. The star's brightness also changed irregularly, sometimes for days and even months at a time. A search of the 150,000-plus in Kepler's database found nothing like this.

So Marengo and two other astronomers decided to take a close look at the star using data taken with the Infrared Array Camera of NASA's Spitzer Space Telescope. They report their findings in a paper recently published online by The Astrophysical Journal Letters.

Their conclusion?

"The scenario in which the dimming in the KIC 8462852 light curve were caused by the destruction of a family of comets remains the preferred explanation …," wrote the three – Marengo; Alan Hulsebus, an Iowa State doctoral student; and Sarah Willis, a former Iowa State graduate student now with the Massachusetts Institute of Technology's Lincoln Laboratory.

Questions about the star were launched last month when a research team led by Tabetha Boyajian of Yale University reported on the star in the Monthly Notices of the Royal Astronomical Society. The astronomers reported how tagged the star's deep and irregular dips in brightness as "bizarre" and "interesting."

Boyajian and the other researchers looked at the data and investigated several possible causes. They wrote the "most promising theory" was a barrage of crumbling comets passing in front of the star.

In a subsequent paper submitted to the Astrophysical Journal, Jason Wright and colleagues at Penn State University speculated about other causes, including alien megastructures built to harvest energy while orbiting the star.

When the Iowa State astronomers studied the star with Spitzer infrared data from January 2015 – two years after the Kepler measurements – Marengo said they didn't see much. If there had been some kind of catastrophe near the star, he said there would be a lot of dust and debris. And that would show up as extra infrared emissions.

Marengo said the study looked at two different infrared wavelengths: the shorter was consistent with a typical star and the longer showed some infrared emissions, but not enough to reach a detection threshold. The astronomers concluded there were no excess and therefore no sign of an collision, a giant impact on a planet or a of rock and debris.

So Marengo and his colleagues say the destruction of a family of comets near the star is the most likely explanation for the mysterious dimming. The comet fragments coming in rapidly at a steep, elliptical orbit could create a big debris cloud that could dim the star. Then the cloud would move off, restoring the star's brightness and leaving no trace of excess infrared light.

And the alien megastructure theory?

"We didn't look for that," Marengo said. "We can't really say it is, or is not. But what the star is doing is very strange. It's interesting when you have phenomena like that – typically it means there's some new physical explanation or a new concept to be discovered."

Explore further: Mysterious star stirs controversy

More information: KIC 8462852: The Infrared Flux. Astrophysical Journal Letters, Volume 814, Number 1 DOI: 10.1088/2041-8205/814/1/L15/meta

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1 / 5 (1) Nov 25, 2015
A light curve caused by the destruction of a family of comets would repeat at approximately equal intervals. Well, is it?
Mordechai Mineakoitzen
1 / 5 (2) Nov 25, 2015
Are they not keeping track of this star since then? Have the dips in brightness stopped entirely, or continued? If they've stopped, any "alien structure" theory likely goes out the door, doesn't it?

Would a string of comets cause us to lose that much light, 22 percent of output, if this was with our own sun? Seems unlikely.
1.7 / 5 (6) Nov 26, 2015
Another "Haw Haw" farcical so called 'explanation' that can only be 'accepted' by coercion. What do these holdeovers from the 'Blue Book' days fear? Why are these patent big lies being peddled to the monopoly mass media? Why does the mass media print them? No one in their right mind will continue to believe this crap that is so bad that any public speaker would have to soak his face in wet cement and let it dry so he/she could parrot it to the public with a straight face!! Any so called 'comets' would have aeons ago became part of the central star inasmuch as most ALL comets are in long elliptical orbits or in their star's Oort Cloud, etc. We would see similar in our own system and we do not. Our system is typical of what is in the wild. Just wait till some Russian prospector finds some artifact on one of the 'asteroids' here while mining. And by the way the 'Guv' is being Awful QUIET about those lights on Ceres lately. What do they REALLY know and WHEN did they KNOW it??!
4.3 / 5 (6) Nov 27, 2015
A light curve caused by the destruction of a family of comets would repeat at approximately equal intervals.

Another "Haw Haw" farcical so called 'explanation' that can only be 'accepted' by coercion.

Unfixably delusional, put in "loss sector" of human progress.
Enthusiastic Fool
3.7 / 5 (6) Nov 28, 2015

the 'Guv' is being Awful QUIET about those lights on Ceres lately. What do they REALLY know

Yeah! Thank God the initial pictures were "leaked" to us by an anonymous group known only as Without NASA leaking those pictures of Ceres the government might have been able to keep them entirely secret! Those brave individuals working at NASA for the good of mankind above all else have my eternal gratitude for sharing the truth with us.

NASA also leaked a follow-up story indicating that the lights are actually just salts. Why is the "GUV" hiding this? Morton's and the Big Salt lobby must be trying to keep prices high at a staggering $150(USD) per ton...

3 / 5 (2) Nov 30, 2015
Osiris1 makes a good point though, the lights of Ceres are seen to be emitting even when the rotation and reflective angle dictate that it would be impossible for it just be a reflection. I am also very sceptical of the idea that this could be a comet as it would have to be phenomenally large to blot out so much light.

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