In 2015, a star dubbed as KIC star 8462852 caused a stir inside and beyond the astronomical community due to rapid and unexplained dimming events detected by the Kepler telescope.
The star’s behavior has continued to frustrate scientists’ efforts to understand it ever since.
Recent discoveries by Josh Simon and Benjamin Shappee of Carnegie and his collaborators provide a longer study of the star, dating back to 2006 before the strange behavior was even detected by Kepler.
Astronomers had thought that the star was only getting weaker over time, but the new study shows that it also became significantly clearer in 2007 and 2014. These unexpected episodes complicate or rule out almost all ideas proposed to explain the observed strangeness of the star.
It’s as if we’ve never encountered anything like it in the universe, or better said, nothing that can explain the star’s behavior ‘naturally.’
Speculation to explain the dimming in the brightness of KIC 8462852 has varied from astronomers proposing the star had swallowed a nearby planet to an unusually large group of comets orbiting the star, and even a massive alien megastructure, built by an extremely advanced alien civilization to harness energy from the sun.
In general, stars appear to darken because a solid object such as a planet or a cloud of dust and gas transiting between it and the observer, eclipsing and attenuating its brightness for a time.
Despite all efforts to understand what was going on at the distant star, the erratic darkening periods seen in KIC 8462852 were different from what astronomers had previously observed anywhere else.
Last year, Simon and Ben Montet (then at Caltech, now at the University of Chicago), who are also co-authors on this study, found that from 2009 to 2012, KIC 8462852 declined by almost 1 percent.
Its brightness then dropped an extraordinary 2 percent in just six months, staying at that level during the last six months of Kepler’s observations.
However, the research team wanted to examine KIC 8462852 for a longer period of time. Thus, they examined nearly 11 years of ASAS (All Sky Automated Survey) observation data and about two years of more recent ASAS-SN (All-Sky Automated Survey for Supernovae) data.
They found that the star has continued to darken since 2015 and is now 1.5 percent weaker than in February of that year.
“Up until this work, we had thought that the star’s changes in brightness were only occurring in one direction—dimming,” Simon explained.
“The realization that the star sometimes gets brighter in addition to periods of dimming is incompatible with most hypotheses to explain its weird behavior.”
“An important next step will be to determine how the color of the star changes with time, especially during its brief dips in brightness,” added Shappee in a statement. “That information would help narrow down the possible explanations for why this star is doing such strange things.”
For example, if the darkening was caused by the dust that obscures the star, then it would seem to become redder as it fades. But if large objects blocked the light of the star, then there would be no change of color.
“We have not solved the mystery yet,” Simon concluded.
“But understanding the long-term changes of the star is a key piece of the puzzle.”