text: Story highlights A star system caught extraterrestrial intelligence experts' attention in October after an unusual light pattern was observed 
   
   After monitoring a space anomaly for two weeks, SETI says it has not detected radio signals 
   
   NASA says the star was likely surrounded by comets 
   
   (CNN) An anomaly in deep space that has been the focus of speculation and observation for weeks over possible extraterrestrial life may have just been solved. 
   
   A research team from Iowa State University looked at data from NASA's Spitzer Space Telescope, and found that the strange dips in light, which were initially theorized to be possible structures, were likely a "swarm of comets." 
   
   The system, KIC 8462852, had been under scrutiny since its unusual light fluctuation was discovered by users of the online astronomy crowdsourcing site Planet Hunters. The group uses publicly available data gathered by NASA's Kepler Telescope, which has been tasked with finding Earth-like planets by searching for the periodic dimming of stars that might suggest such a planet is passing by. 
   
   But NASA says the Kepler Telescope only viewed the star in "visible light," and in this case, they searched by infrared light. 
   
   "It's possible that a family of comets is traveling on a very long, eccentric orbit around the star," NASA said in a statement. "At the head of the pack would be a very large comet, which would have blocked the star's light." 
   
   Read More ||||| A star called KIC 8462852 has been in the news recently for unexplained and bizarre behavior. NASA's Kepler mission had monitored the star for four years, observing two unusual incidents, in 2011 and 2013, when the star's light dimmed in dramatic, never-before-seen ways. Something had passed in front of the star and blocked its light, but what? 
   
   Scientists first reported the findings in September, suggesting a family of comets as the most likely explanation. Other cited causes included fragments of planets and asteroids. 
   
   A new study using data from NASA's Spitzer Space Telescope addresses the mystery, finding more evidence for the scenario involving a swarm of comets. The study, led by Massimo Marengo of Iowa State University, Ames, is accepted for publication in the Astrophysical Journal Letters. 
   
   One way to learn more about the star is to study it in infrared light. Kepler had observed it in visible light. If a planetary impact, or a collision amongst asteroids, were behind the mystery of KIC 8462852, then there should be an excess of infrared light around the star. Dusty, ground-up bits of rock would be at the right temperature to glow at infrared wavelengths. 
   
   At first, researchers tried to look for infrared light using NASA's Wide-Field Infrared Survey Explorer, or WISE, and found none. But those observations were taken in 2010, before the strange events seen by Kepler -- and before any collisions would have kicked up dust. 
   
   To search for infrared light that might have been generated after the oddball events, researchers turned to Spitzer, which, like WISE, also detects infrared light. Spitzer just happened to observe KIC 8462852 more recently in 2015. 
   
   "Spitzer has observed all of the hundreds of thousands of stars where Kepler hunted for planets, in the hope of finding infrared emission from circumstellar dust," said Michael Werner, the Spitzer project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, and the lead investigator of that particular Spitzer/Kepler observing program. 
   
   But, like WISE, Spitzer did not find any significant excess of infrared light from warm dust. That makes theories of rocky smashups very unlikely, and favors the idea that cold comets are responsible. It's possible that a family of comets is traveling on a very long, eccentric orbit around the star. At the head of the pack would be a very large comet, which would have blocked the star's light in 2011, as noted by Kepler. Later, in 2013, the rest of the comet family, a band of varied fragments lagging behind, would have passed in front of the star and again blocked its light. 
   
   By the time Spitzer observed the star in 2015, those comets would be farther away, having continued on their long journey around the star. They would not leave any infrared signatures that could be detected. 
   
   According to Marengo, more observations are needed to help settle the case of KIC 8462852. 
   
   "This is a very strange star," he said. "It reminds me of when we first discovered pulsars. They were emitting odd signals nobody had ever seen before, and the first one discovered was named LGM-1 after 'Little Green Men.'" 
   
   In the end, the LGM-1 signals turned out to be a natural phenomenon. 
   
   "We may not know yet what's going on around this star," Marengo observed. "But that's what makes it so interesting." 
   
   Ames manages the Kepler and K2 missions for NASA's Science Mission Directorate. JPL managed Kepler mission development. Ball Aerospace & Technologies Corp. operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. 
   
   JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. 
   
   Caltech manages JPL for NASA. 
   
   For more information about Kepler and Spitzer, respectively, visit: 
   
   http://www.nasa.gov/kepler 
   
   http://kepler.nasa.gov 
   
   http://www.nasa.gov/spitzer 
   
   http://www.spitzer.caltech.edu 
   
   News Media Contact 
   
   Whitney ClavinJet Propulsion Laboratory, Pasadena, California818-354-4673whitney.clavin@jpl.nasa.govMichele JohnsonAmes Research Center, Moffett Field, Calif.650-604-6982michele.johnson@nasa.gov2015-357 ||||| 
   
   The alien star probably has a band of eccentric comets. (NASA/JPL-Caltech) 
   
   If you were still holding out hope for aliens hanging out around KIC 8462852, I've got some bad news for you. Researchers at Iowa State University think they've found an explanation for the star's weird behavior. Spoiler alert: It's not aliens. 
   
   In October, scientists spotted a distant star that was blinking in an unusual fashion. Unlike most of the stars spotted by the Kepler telescope — which keeps an eye on fluctuations in light to help detect planets passing in front of distant suns — this one was dimming irregularly. 
   
   [Why NASA’s top scientist is sure that we’ll find signs of alien life in the next decade] 
   
   Experts pointed out that the star's light was winking in and out of view in a way that could presumably possibly be the result of some massive orbiting alien structure. The scientists didn't really think that our space telescopes had caught sight of an "alien megastructure," but there's no harm in hoping. 
   
   Since then, the Search for Extraterrestrial Intelligence (SETI) institute has turned its radio telescopes to the strange star — and they haven't heard any of the radio signals we'd expect from the goings-on of an intelligent civilization. 
   
   [Scientists caught a new planet forming for the first time ever] 
   
   A cluster of comets had been floated as one possible explanation. Now, in a study published in the Astrophysical Journal Letters, Massimo Marengo of Iowa State University (along with his doctoral student Alan Hulsebus and former student Sarah Willis, now a researcher at the Massachusetts Institute of Technology’s Lincoln Laboratory) suggests it's the most likely one. 
   
   Marengo and Co.'s work didn't actually rule out an alien megastructure, but it did rule out other, more likely explanations — like massive planetary or asteroid collisions. Looking at the star in infrared light didn't reveal the hot dust one would expect from such violent activity. That makes the most likely (non-alien) explanation a set of cold comets — ones that have been orbiting the planet for a while, causing different levels of dimming based on their assorted sizes and transit periods. 
   
   "This is a very strange star," Marengo said in a statement. "It reminds me of when we first discovered pulsars. They were emitting odd signals nobody had ever seen before, and the first one discovered was named LGM-1 after 'Little Green Men.'” 
   
   Pulsars turned out to be very weird — but they weren't aliens, either. 
   
   "We may not know yet what's going on around this star,” Marengo said. “But that's what makes it so interesting." 
   
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   Mars might get rings just like Saturn’s one day ||||| AMES, Iowa – 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 star brightness 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 stars 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 citizen scientists 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 infrared emissions and therefore no sign of an asteroid belt collision, a giant impact on a planet or a dusty cloud 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.”
target: – KIC 8462852 is an odd and fascinating star, astronomers say—but it probably isn't host to an "alien megastructure," as some researchers suggested as a longshot possibility when the star and its highly unusual dimming pattern first came to attention. Instead, Iowa State University researchers who studied infrared light emitted by the star in the Cygnus constellation believe that the likeliest explanation is the "destruction of a family of comets," which caused dramatic changes in the light observed by the Kepler telescope as the fragments and debris cloud moved past the star in a long, elliptical orbit. The team didn't actually look for alien structures, but they were able to use the infrared data to rule out possibilities including a massive collision nearby, the Washington Post reports. The SETI Institute has also investigated the star, and found no trace of the radio signals that would suggest extraterrestrial technology was present, CNN reports. But even without aliens, nothing like what is happening around KIC 8462852 has ever been seen before and astronomers want to learn more. "This is a very strange star," lead researcher Massimo Marengo said in a NASA press release. "It reminds me of when we first discovered pulsars. They were emitting odd signals nobody had ever seen before, and the first one discovered was named LGM-1 after 'Little Green Men.'" "We may not know yet what's going on around this star," he added "But that's what makes it so interesting." (Closer to home, astronomers have discovered that Mars is destroying its own moon.)