http://www.cnn.com/2016/01/16/us/space-anomaly-remains-mystery/index.html

 

Remember that space anomaly of the dimming star that had everyone crying “aliens”? Well, it’s still as mysterious as ever.

Theories surrounding the star system KIC 8462852, also known as Tabby’s Star, ranged from comets to an “alien megastructure” after the online astronomy crowdsourcing site Planet Hunter discovered an unusual light fluctuation in the star system a few years ago.
A new analysis of KIC 8462852 shows that the star system, which lies about 1,500 light years away, has been gradually dimming for more than a century, and it’s likely not caused by a cloud of orbiting comets.
Bradley Schaefer, a physics and astronomy professor at Louisiana State University, examined data from a Harvard University archive of digitally scanned photographic plates of the sky dating back more than a century. He averaged the data and noticed that the star system also dimmed between 1890 and 1989.
“This star’s dimming is unique and inexplicable,” Schaefer told CNN.
Tabby’s Star is an F-type main sequence star. This type of star does not dim by 20%, as Tabby’s Star has shown, he explained. “Millions of these stars have been monitored for this sort of thing, and they don’t fade,” he said.
The data from the photographic plates was also examined by Yale postdoctoral astronomy fellow Tabetha Boyajian, who is on Planet Hunters’ advisory team. She and other colleagues published an academic paper in September that theorized the dimming light could be from comet fragments.
But the probability of a comet family creating the erratic dip in brightness is highly unlikely, Schaefer said.
“The century-long dimming trend requires an estimated 648,000 giant comets… all orchestrated to pass in front of the star within the last century,” he writes in the research paper.
“The trouble is that Tabby’s Star, it’s a perfectly ordinary star. The only thing that was unusual about the star was the dip seen by Kepler,” he said.
NASA’s Kepler Telescope, which is on a mission to find Earthlike planets, documented KIC 8462852’s abnormality after monitoring the star system from 2009 to 2013.
Ordinarily, a star will dip in brightness as planets pass by them, but KIC 8462852 has displayed irregular fluctuations of light that sometimes decreasing by as much as 20% in brightness.
The Search for Extraterrestrial Intelligence Institute (SETI) started monitoring Tabby’s star after NASA’s Kepler team vetted the data showing the unusual light patten.
In November, SETI’s senior astronomer Seth Shostak told CNN they hadn’t picked up any radio signals from the star system. But that doesn’t rule out intelligent life in KIC 8462852.
“There is estimated to be in our galaxy alone a trillion planets. And we can see 100 billion galaxies,” Shostak said. “It’s believed that one in 10 stars may have a habitable world capable of supporting life.”
The discovery of a strange star could mean alien life
The discovery of a strange star could mean alien life 01:46
The comet-family theory as well as other explanations for Tabby’s star dimming have all been refuted, Schaefer said. But there might be two other possible solutions.
“Either nature has found a hidden loophole, or hey, maybe there is a totally new idea,” Schaefer said.
So what about the possibility of aliens? That explanation doesn’t rank high on Schaefer’s list. “I too, like everyone else, would be astounded if those ideas could be proven true. But we’re going for the facts.”
For now astronomers still cannot explain what’s going on with KIC 8462852.
“It’s a normal star behaving weirdly,” Schaefer said. “We’ve got ourselves a classic mystery.”

Astronomers really want to know what’s happening around a star that’s 1,480 light-years away.

In October, astronomers floated the idea that the star KIC 8462852 could be surrounded by some sort of huge alien structure. While that’s unlikely, scientists are still having a hard time coming up with a good explanation for the star’s strange behavior.

Every so often, the star’s light dims by as much as 20 percent. By comparison, a huge, Jupiter-size planet orbitiing the star would block out about 1 percent of the star’s light. Astronomer Jason Wright proposed that a swarm of objects, perhaps alien solar panels, could be circling the star and causing the dimming. Scientists have since listened for radio and lasercommunications from this hypothetical alien civilization, but found nothing.

Up until now, the leading hypothesis was that a family of comets circles the star, occasionally clumping together to block out huge portions of its light. A new paper, published on the arXiv, says that this explanation is unlikely as well.

You would need 648,000 giant comets to explain the star’s dimming pattern.

Within the paper (which hasn’t been peer-reviewed yet), astronomer Bradley Shaefer from Louisiana State University describes his deep dive into Harvard’s historical astronomy plates. After looking at 1,232 photographic plates from the past century, he found that the star not only dims dramatically over short periods of time today, but also that the star has been growing dimmer over time. These two very strange phenomena are probably linked.

In the past century or so, the star’s brightness has dipped by 16.5 to 19.3 percent. This trend is “completely unprecedented” for a star of this type, Schaefer writes. “Such stars should be very stable in brightness, with evolution making for changes only on time scales of many millions of years.”

He goes on to calculate how many comets would be needed to explain the phenomena, and the answer is: a whole heck of a lot.

Previously, scientists estimated that it would require 36 giant comets to explain the occasional 20 percent dip in light from the star. To explain the century-long fading, Shaefer calculates you’d need 648,000 comets with a diameter of 200 kilometers (124 miles) each. By comparison, the largest known comet in our solar system is 60km in diameter. And the hypothetical comets around KIC 8462852 would need to have a total mass that’s four times the mass of everything in the Kuiper belt.

“I do not see how it is possible for something like 648,000 giant comets to exist around one star, nor to have their orbits orchestrated so as to all pass in front of the star within the last century,” Shaefer writes. “So I take this century-long dimming as a strong argument against the comet-family hypothesis to explain the Kepler dips.”

While Schaefer doesn’t offer an alternative theory, his analysis provides a second line of data suggesting there really is something weird happening around KIC 8462852–that it’s not just a fluke of the Kepler telescope that discovered the star’s odd behavior.

Just because science doesn’t yet have an explanation for what’s happening at KIC 8462852 doesn’t mean it’s aliens. Most major discoveries don’t have an obvious explanation at first. But whatever is happening on this faraway star, it’s sure to be something interesting.

[arXiv via Gizmodo]

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