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Monday, August 8, 2016

'Dyson sphere' star found to be dimming dramatically - and nobody knows why

Alien megastructure mystery deepens: 'Dyson sphere' star found to be dimming dramatically - and nobody knows why
This star is breaking all the rules.
Bizarre readings from star called KIC 8462852 have baffled scientists
One theory is dips in light caused by structure similar to Dyson sphere
Others suggest break up of huge comets would block the starlight
A Kickstarter campaign to investigate has reached its £68,352 target
The star KIC 8463853 has a dark secret. Literally. In 2011 and 2013, the light from this star plummeted by as much as 20 percent, suggesting that something very big must be blocking the light. Like, something 20 times the size of Jupiter. Scientists have speculated that comets, gobs of dust, or even a large alien structure could be causing the dimming, but so far, none of the explanations really works.
Now, a paper that was just published to the arxiv has found that the star dimmed by an unprecedented amount over the whole four years that the Kepler telescope kept an eye on it. It's not known whether this phenomenon is connected to the huge but short-duration dips from 2011 and 2013.
Big Dipper
In new study, which is not yet peer-reviewed, astronomers Ben Montet and Joshua Simon measured the light from the star (known informally as "Tabby's Star") that the Kepler telescope recorded during its four-year mission. And they found some pretty strange activity.
For the first few years, Tabby's Star dimmed at about 0.34 percent per year. Then its light level dropped dramatically by about 2.5 percent in 200 days. After that it returned to the original slow fade rate.
The authors looked at 500 other stars in the vicinity of Tabby's Star, as well as 500 other stars that are similar in size and makeup to Tabby's Star, but none of the others experienced such a dramatic drop in light levels. Their brightness remained essentially unchanged.
A Long-Term Trend?
Previously, old astronomy plates indicated the star has been dimming for the past century, which would require a seemingly impossible number of giant comets to explain the trend. However, scientists disagree over those findings, and the debate over long-term dimming remains inconclusive.
The Kepler telescope's high precision data show that the star was definitely dimming over the 4 years that Kepler monitored this star, suggesting that the long-term dimming hypothesis is possible, but scientists still can't say for sure.
"These results introduce us to another delightfully unexpected piece of the puzzle," says Tabetha Boyajian, one of the star's discoverers and the namesake of the Tabby's Star nickname.
"Tabby's star continues to defy easy explanation!" Keivan Stassun, who has studied the star's long-term light patterns, told Popular Science in an email. "These intriguing new findings suggest that none of the considered phenomena can alone explain the observations. Of course, the star doesn't have to abide by our hope for a single explanation. In the end, figuring out this puzzle may require accounting for a combination of effects."
Defying Explanation
Scientists differ in their favorite explanations for what's happening around Tabby's Star. While Boyajian still thinks the most likely explanation is a group of cold comets, Montet thinks the evidence is growing that a large cloud of dust is blocking the star's light.
"Tabby's star continues to defy easy explanation."
If the light were being blocked by comet or dust (or an alien Dyson swarm, for that matter), scientists would expect to see extra heat energy coming from around the star. So far they don't, but Montet wonders if taking deeper measurements will find the missing energy.
"There's a lot of explanations that explain half or two-thirds of story, but there's nothing that fully explains everything," he says.
Although many uncertainties remain, the possibility that the weird blips in light are being caused by some previously undiscovered star behavior is at least seeming less likely, according to Montet.
"To have one thing that we haven't seen before might be explainable with a stellar mechanism, but this is a few things now. It seems unlikely we would miss a stellar mechanism that fits all of these."
Finding An Answer
To find out what's causing KIC 8462852's mysterious behavior, scientists want to study it while it's in the midst of one of the major dips, like the ones that happened in 2011 and 2013.
Although the Kepler telescope is no longer able to keep an eye on Tabby's Star, Boyajian's team recently won funding to continue monitoring the star using the Las Cumbres Observatory Global Telescope Network (LCOGT). If any funny business is detected, networks of astronomers--both professional and amateur--will be contacted immediately in order to collect as much data about the dimming event as possible.
Observations from the ground, like those of the LCOGT, aren't as precise as those of a space telescope like Kepler, but an upcoming telescope from the European Space Agency could also lend a hand.
PLATO (PLAnetary Transits and Oscillations of stars) will be like "Kepler on steroids," says Montet. The space-based telescope is expected to spend a few years studying the same region that Kepler monitored. The telescope is expected to launch in 2024.
In the meantime, the mystery surrounding Tabby's Star only deepens.………

Cecile G. Tamura

Artist illustration of a crumbling Dyson sphere

Danielle Futselaar/SETI International

What is a Dyson Sphere ?

A proposed method for harnessing the power of an entire star is known as a Dyson sphere.

First proposed by theoretical physicist Freeman Dyson in 1960, this would be a swarm of satellites that surrounds a star.

They could be an enclosed shell, or spacecraft spread out to gather its energy - known as a Dyson swarm.

If such structures do exist, they would emit huge amounts of noticeable infrared radiation back on Earth.

But as of yet, such a structure has not been detected.

Source: All About Space magazine

Interest in the star, which is 1,480 light-years away, began last October when Yale scientists found unusual fluctuations in its light - with some suggesting the dips in light are caused by an alien megastructure. One theory that has got traction says the dips are caused by an alien megastructure, similar to a Dyson sphere (stock image)

Credit : Jay Wong/ All About Space Magazine

KIC 8462852, located 1,480 light-years away, was monitored by the Kepler Space Telescope for more than four years, beginning in 2009.

As a planet passes in front of a star's light it causes the light to dim, and Kepler can capture these fluctuations.

Typically this light dims in a symmetrical pattern.

However, during Kepler's study into KIC 8462852 the researchers noticed it went through 'irregularly shaped, aperiodic dips.'

In some cases, the flux dropped down to below the 20% level and lasted between 5 and 80 days at a time.

Some stars don't have uniformly bright discs and spin at such a high rate that they have an spheroidal shape.

This causes them to have a larger radius at the equator than at the poles.

The poles, with their smaller radius, have a higher surface gravity meaning they are hotter and brighter - or 'gravity brightened.'

Meanwhile, the equator is cooler and darker, which is known being 'gravity darkened.'

Mr Galasyn suggests that the dips and increases in flux of KIC 8462852 are caused as planets move across these brighter and darker areas.

Two of the dips, on day 1520 and 1570 of Kepler's mission, are shown having a similar shape but a different magnitude.

Despite their differences, both curves follow the shape of a planet travelling across a brightened pole, as suggested by the paper.

Mr Glasnyn claims that the two dips could be caused by two planets moving in front of the star.

If the first planet is large it could block out around 20% of the star's disc, while a smaller planet could occlude just 8% of it.

The second dip may be shorter because the smaller planet is moving faster and orbiting closer to the star.

Astronomers have been looking for answers about what is causing the bizarre light fluctuations around the star KIC 8462852 (pictured) for weeks. Some have suggested it is an alien megastructure such as a Dyson sphere. The strange structure was spotted by researchers from Yale

Dredit : Arxiv

Ruling out an alien structure

In order to explore the idea that such a structure could have been built by intelligent alien life, the Extraterrestrial Intelligence Institute, Seti, trained its Allen Telescope Array on the star for more than two weeks.

Experts looked for two types of radio signal: narrow-band signals generated as a 'hailing signal' for alien societies wanting to announce their presence, and broad-band signals.

These signals would be produced by 'beamed propulsion'.

Seti said that if large scale alien engineering projects really are underway, the array would pick up signals made by intense microwave beams that could be used to power spacecraft.

Scientists analysing the data found no clear evidence for either type of signal.

They believe this rules out the presence of omnidirectional transmitters - large antenna - of approximately 100 times today's total terrestrial energy usage in the case of the narrow-band signals, and ten million times that usage for broad band emissions.
So the presence of a Dyson sphere is unlikely.