One of the most mysterious stars in the galaxy may soon be explained: ScienceAlert

By | September 18, 2023

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 yellowish-white glow about 1,470 light-years away — and its strange short-term brightness fluctuations and long-term changes have defied even now the scientists’ attempts at explanation. .

There are several candidates for what might be happening, but progress has stalled due to a lack of more detailed information. But we won’t have to wait much longer.

Led by astronomer Massimo Stiavelli of the Space Telescope Science Institute (STScI), a team has made observations of Boyajian’s Star using the James Webb Space Telescope and is setting out to decipher them.

“KIC 8462852 (Boyajian’s Star) exhibits an extraordinary light curve, showing deep ‘dipping’ events and long-term changes,” the team wrote in their proposal.

“We propose observations of this object in the 1.7 to 25 micron wavelength range in order to measure the thermal emission from the circumstellar material that causes the observed variations in the light curve.”

Boyajian’s Star, named after Louisiana State University astrophysicist Tabetha Boyajian who led the paper that announced the discovery of its strangeness, has been a puzzle since 2015. Since its discovery, it has been observed dimming, multiple times, in up to 22 percent of your normal. shine. And records show this has been happening 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, which typically always block the same small percentage of light. Boyajian’s Star dims erratically, at different depths, with no discernible pattern in the timing of the dips.

A single 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, records show that it also went through periods of significant brightness. It really is an absolute oddity (though perhaps not the only one of its kind).

Explanations for the star’s dimming range from the relatively simple – dust clouds or orbiting debris – to the outlandish, the “alien megastructure” hypothesis that propelled Boyajian’s Star to terrestrial fame. This has since been scrapped, but it hasn’t brought us much closer to an answer.

The fact that infrared wavelengths of light undergo dimming more quickly than ultraviolet bands suggests that whatever is causing the dips is not a solid object.

Options include comet swarms, debris from a fragmented exoplanet that got too close to the star, debris from a fragmented exomoon, some kind of strange internal fluctuations (Betelgeuse, anyone? OK, different kind of star, but still, not impossible! ), and a lumpy cloud of dust.

KIC 8462852 in infrared (left) and ultraviolet (right). (Infrared: IPAC/NASA; Ultraviolet: STScI/NASA)

It’s also possible that there’s something going on that we haven’t thought of yet! Stiavelli and his colleagues hope that JWST observations, collected in the near- and mid-infrared with NIRSpec and MIRI, will help narrow it down. Especially since infrared wavelengths penetrate dust more efficiently than shorter wavelengths, and the JWST is a powerful infrared telescope.

“The first objective of these observations is to distinguish between competing models for the star’s behavior: a detection would confirm the circumstellar nature of the occulting material; a non-detection would be highly restrictive and would motivate the development of alternative models for the bending star’s light, such as dense knots of material in the interstellar medium, or a cold intervening disk of a dark object such as a black hole,” they write in their proposal.

“The second objective of these observations, in the event of a detection, is to determine the temperature and luminosity of the circumstellar dust to better understand this extraordinary object.”

We don’t have any more answers yet – researchers are probably hard at work analyzing the new spectra and figuring out what they mean – but since the program has been marked as complete, we hope it won’t take too long.

In the meantime, we will be anxiously waiting.

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