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A new clue has just been found that could help solve the mystery of a weirdly dimmed star. KIC 8462852, also known as Boyajian’s Star, appears to have a binary companion that could contribute to its irregular drops in brightness.
If confirmed by more detailed observations, the newly discovered companion star could help astronomers finally solve the current mystery of KIC 8462852.
The star was discovered in 2015 by astronomer Tabetha Boyajian (so she was previously Tabby’s star), and since then it has proven to be quite a headache. It’s a yellow-white dwarf star about 1,470 light-years away, and it continues to darken erratically. There is no regularity either in the timing of the star’s gradation, or in the depth – some of the starlight drops have been as deep as 22%.
This behavior excludes the planets; when an exoplanet passes between a star and orbiting Earth, it will darken the star by a tiny amount – 1% or less – at regular intervals.
Also, when Boyajian’s star darkens, some wavelengths are blocked more than others. This excludes a solid object (like an alien megastructure, as proposed in 2016), which would block all wavelengths in the same way.
So far, the most likely explanation seems to be optically thin dust and debris, likely from fragmented planetesimals or comets in eccentric orbits, in combination with normal variations in brightness of the star itself.
The presence of a binary companion star in a large orbit could help explain the presence of all this material, providing additional gravitational disturbances to disrupt orbiting bodies.
Since 2016, a team of astronomers led by Logan Pearce of the University of Arizona have been trying to confirm the potential connection of a nearby star to KIC 8462852. Their paper has now been accepted in The astrophysical journal.
The difficulty of measuring space in three dimensions is what made this job quite difficult. Stars that appear close enough can actually be at vastly different distances from the viewer. So Pearce and his team used five years of observations to make precise astrometric measurements of the faint star that appeared to be close to KIC 8462852.
“In this work, we use three epochs of Keck / NIRC2 astrometry spanning five years to review the status of KIC 8462852’s close mate, and show that they are a common proper motion pair and a gravitationally related binary system. », They wrote in their paper.
In addition to observations from the Keck Observatory, the 2020 release of astrometric data from the Gaia satellite – the most complete and accurate three-dimensional map of the Milky Way to date – also included the pale star, with measurements in agree with the team’s findings.
The two stars are separated by a distance of 880 astronomical units. Boyajian’s star, or KIC 8462852 A, is the largest star, with about 1.36 times the mass and 1.5 times the size of the Sun. The companion, KIC 8462852 B, is a red dwarf star about 0.44 times the mass and 0.45 times the size of the Sun.
In such a large orbit, KIC 8462852 B is unlikely to have a direct effect on the brightness of KIC 8462852 A. But it could still play a role in the larger star’s mysterious fluctuations, the researchers said.
“The binary companion can influence the long-term evolution of the system,” they wrote in their article.
Scientists have already discovered that widely spaced stellar binaries can be pushed by larger gravitational forces to move very close to their mutual center of mass several times over the course of about 10 billion years.
In turn, this could lead to the disruption of planets and other small orbiting bodies where they are stretched and torn apart by gravitational interactions, resulting in clouds of debris.
The scenario remains to be confirmed. At such a wide separation, the two stars would have an extremely long orbit, and the observations made were not sufficient to characterize this orbit. KIC 8462852 B could be a star that has been ejected from the system; or the two stars could be members of a co-mobile group.
Researchers believe a binary is the most likely explanation for their measurements of the two stars, but future measurements of the pair will be needed to better understand their relationship. This could help confirm or rule out the role of KIC 8462852 B in the star’s erratic luminosity.
But for all mystery lovers, fear not. There are other oddly subdued stars, including a star for which the binary companion has already been considered, and a tantalizing collection of 21 stars that could be even weirder.
The team’s research was accepted in The astrophysical journal, and is available on arXiv.
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