One of the most mysterious stars in the Milky Way may soon have an explanation for its strange behavior.
It’s called Boyajian’s Star, or KIC 8462852—less formally known as Tabby’s Star, a yellow-white flash some 1,470 light-years away—and its strange short-term brightness fluctuations and long-term changes have so far defied scientists’ attempts to explain it. .
There are several candidates for what might happen, but progress has stalled due to a lack of more detailed information. But we won’t have to wait long.
A team led by astronomer Massimo Stiavelli of the Space Telescope Science Institute (STScI) made observations of Boyajian’s star using the James Webb Space Telescope and is committed to deciphering them.
“KIC 8462852 (Boyajian’s Star) displays an extraordinary light curve that shows both deep ‘dip’ events and long-term changes,” the team wrote in their proposal.
“We propose to observe this object in the wavelength range of 1.7 to 25 microns to measure the thermal emission from the circumstellar material causing changes in the observed light curve.”
JWST/MIRI raw image titled “Understanding the Origins of Battle Star Obscurations”.
Photographed on 8/5/2023 10:23:14 PM. pic.twitter.com/hoBSLBNVCM
— Jwst Feed (@WebbFeed) August 7, 2023
Boyajian’s Star, named after Louisiana State University astrophysicist Tabetha Boyajian, who led the paper heralding the discovery of its strangeness has been a puzzle since 2015. Since its discovery, it has been observed to dim up to 22 percent of its normal brightness several times. And the records show that he has been doing this repeatedly for years.
Scientists know of phenomena that can cause a star’s light to dim. The most obvious example is an orbiting exoplanet. But exoplanets cause periodic dips in starlight, usually blocking the same small percentage of light each time. Boyajian’s Star dims irregularly, at different depths, with no apparent pattern in the timing of the dips.
A one-off dip could be an occultation or something random passing between us and the star. But that’s not what we saw with Boyajian’s Star either. In fact, the records show that he also went through periods of significant clarity. He really is an absolute freak (though perhaps not the only one of his kind).
Explanations for the star’s dimming range from the relatively straightforward—orbiting clouds of dust or debris—to the strange hypothesis of an “alien megastructure” that shot Boyajian’s star to earthly fame. That has since been ruled out, but that didn’t get us much closer to an answer.
The fact that infrared wavelengths of light pass through dimming more easily than ultraviolet bands suggests that whatever is causing the dips is not a solid object.
Possibilities include comet swarms, debris from a torn-up exoplanet that got too close to a star, debris from a dismembered exomoon, some weird internal fluctuations (Betelgeuse, anyone? OK, a different kind of star, but still, not impossible!), and a patchy cloud dust.
It’s also possible that something is going on that we haven’t thought of yet! Stiavelli and his colleagues hope that JWST observations collected in the near- and mid-infrared by NIRSpec and MIRI will help narrow it down. Especially since infrared wavelengths penetrate dust more efficiently than shorter wavelengths and JWST is a powerful infrared telescope.
“The first goal of these observations is to distinguish between competing models of the star’s behavior: a detection would confirm the circumstellar nature of the hidden material; a non-detection would be highly constraining and motivate further development of alternative models for the star’s light.” curves such as dense knots of material in the interstellar medium or the encroaching cold disk of a dark object such as a black hole,” they write in their proposal.
“A second goal of these observations, if detected, is to determine the temperature and luminosity of the circumstellar dust to better understand this extraordinary object.”
We don’t have any other answers yet—researchers are probably hard at work analyzing the new spectra and figuring out what they mean—but since the program was marked as completeI hope it won’t be long.
In the meantime, we will wait on the tension hooks.