Tag Archives: KIC 8462852

More strange behavior from Tabby’s Star

Astronomers reviewing past data of KIC 8462852, known as Tabby’s Star to the public, have discovered that not only has it been dimming in a variety of inexplicable ways, it also has brightened twice in a manner that eliminates all past theories for its behavior, including alien megastructures.

The latest findings from Carnegie’s Josh Simon and Benjamin Shappee and collaborators take a longer look at the star, going back to 2006—before its strange behavior was detected by Kepler. Astronomers had thought that the star was only getting fainter with time, but the new study shows that it also brightened significantly in 2007 and 2014. These unexpected episodes complicate or rule out nearly all the proposed ideas to explain the star’s observed strangeness.

Up until now, all the changes to the star had involved dimming, though in ways that did not fit any present theory of stellar evolution. Thus, astronomers theorized that the dimming was caused by something moving in front of the star, from comets to dust to alien structures. This new data of two significant brightening events makes all those theories invalid.

Update: More news about Tabby’s Star: Using two space telescopes as well as amateur telescopes on the ground scientists have determined that the dimming must come from an uneven dust cloud.


The mystery of Tabby’s star deepens

Astronomers looking at the light variations of the star dubbed by some Tabby’s star have become even more baffled.

Spurred by a controversial claim that the star’s brightness gradually decreased by 14 percent from 1890 to 1989, Montet and Simon decided to investigate its behavior in a series of Kepler calibration images that had not previously been used for scientific measurements. “We thought that these data could confirm or refute the star’s long-term fading, and hopefully clarify what was causing the extraordinary dimming events observed in KIC 8462852,” explained Simon.

Simon and Montet found that, over the first three years of the Kepler mission, KIC 8462852 dimmed by almost 1 percent. Its brightness then dropped by an extraordinary 2 percent over just six months, remaining at about that level for the final six months of the mission. The pair then compared this with more than 500 similar stars observed by Kepler and found thata small fraction of them showed fading similar to that seen in KIC 8462852 over the first three years of Kepler images. However, none exhibited such a dramatic dimming in just six months, or a total change in brightness of 3 percent.

“The steady brightness change in KIC 8462852 is pretty astounding,” said Montet. “Our highly accurate measurements over four years demonstrate that the star really is getting fainter with time.  It is unprecedented for this type of star to slowly fade for years, and we don’t see anything else like it in the Kepler data.” 

At the moment, there is no good theory based on what astronomers know of stellar evolution to explain this star’s behavior. This does not mean the only explanation left is that aliens are building a Dyson sphere around the star, but it also leaves everyone at a loss to explain what is happening.


More data says no alien civilization at KIC 8462852

New observations of the star KIC 8462852 to see if an alien civilization had produced laser signals has produced a null result, reinforcing the conclusion that the erratic dimming of the star is not caused by alien megastructures.

On six nights between October 29 and November 28, 2015, scientists searched for pulses as short as a billionth of a second at the Boquete Optical SETI Observatory in Panama, using a 0.5 m Newtonian telescope. The observatory’s relatively small telescope uses a unique detection method having enhanced sensitivity to pulsed signals. If any hypothetical extraterrestrials had beamed intentional laser pulses in the visible spectrum toward Earth, the Boquete observatory could have detected them so long as they exceeded the observatory’s minimum detectable limit.

KIC 8462852 has puzzled astronomers because it shows irregular dimming unlike anything seen for another star. The anomalous light curve was measured using NASA’s Kepler telescope, as part of its search for exoplanets. However, even though a planet the size of Jupiter would cause dimming of approximately 1%, the dimming observed for KIC 8462852 was far greater – up to 22%. Just as strange, the dimming didn’t follow the regular pattern of a planet orbiting a star, but instead was unpredictable. The best explanation to date is that the dimming may have been caused by cometary fragments in a highly elliptical orbit around KIC 8462852, intercepting starlight at the same time the Kepler mission was observing it.


No sign of alien civilization at distant star

The uncertainty of science: Two weeks of targeted observations by the Allen Telescope Array in California have detected no clear signal of an alien civilization at the star KIC 8462852 where Kepler observations have seen variations that could possibly be caused by giant alien structures.

Two different types of radio signals were sought: (1) Narrow-band signals, of order 1 Hz in width, such as would be generated as a “hailing signal” for societies wishing to announce their presence. This is the type of signal most frequently looked for by radio SETI experiments.  (2) Broad-band signals that might be due to beamed propulsion within this star system.  If astroengineering projects are really underway in the vicinity of KIC 8462852, one might reasonably expect the presence of spacecraft to service this activity.  If these craft are propelled by intense microwave beams, some of that energy might manifest itself as broad-band radio leakage. “This is the first time we’ve used the Allen Telescope Array to look for relatively wide-band signals, a type of emission that is generally not considered in SETI searches,” said SETI Institute scientist Gerry Harp.

Analysis of the Array data show no clear evidence for either type of signal between the frequencies of 1 and 10 GHz.  This rules out omnidirectional transmitters 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.

The data shows no sign of alien civilization, but it also does not eliminate the possibility. More detailed observations are required to do that.