A new clue has just been found that could help solve the mystery of a strange fading star. KIC 8462852, also known as Boyajian’s Star, appears to have a binary companion that could contribute to its irregular dives in brightness.
If confirmed with more detailed observations, the new companion star could help astronomers finally solve the ongoing mystery of KIC 8462852.
The star was discovered in 2015 by astronomer Tabetha Boyajian (henceforth it was Tabby’s Star) and has since turned out to be a real puzzle. It is a yellow-white dwarf star, located about 1,470 light-years away, and continues to fade irregularly. There is no regularity in either the fading moment of the star or the depth – some of the dives into starlight were as deep as 22%.
This behavior excludes the planets; when an exoplanet passes between a star and Earth as it orbits, it will dim the star by a small amount – 1 percent or less – at regular intervals.
Moreover, when Boyajian’s Star fades, some wavelengths are blocked longer than others. This excludes a solid object (such as an extraterrestrial megastructure, as proposed in 2016), which would equally block all wavelengths.
So far, the most likely explanation seems to be dust and optically thin debris, possibly from broken planetesimals or comets in eccentric orbits, in combination with normal variations in brightness from the star itself.
The presence of a binary accompanying star in a wide orbit could help explain the presence of this material, providing additional gravitational perturbations to disrupt orbiting bodies.
Since 2016, a team of astronomers led by Logan Pearce of the University of Arizona has been trying to confirm the potential connection of a nearby star to KIC 8462852. Their work has now been accepted into The astrophysics journal.
The difficulty of measuring space in three dimensions is what made this quite difficult. Stars that look quite close could actually be at very different distances from the viewer. So Pearce and the team used five-year observations to make accurate astrometric measurements of the faint star that appeared close to KIC 8462852.
“In this paper we use three epochs of Keck / NIRC2 astrometry that span five years to review the condition of the close companion at KIC 8462852 and show that they are an appropriate common motion pair and a gravitationally bound binary system,” they wrote in the paper .
In addition to Keck’s observations, the launch in 2020 of astrometric data from the Gaia satellite – the most complete and accurate three-dimensional map of the Milky Way to date – also included the faint star, with measurements consistent 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, 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.
At such a wide orbit, KIC 8462852 B would be unlikely to have any direct effect on the brightness of KIC 8462852 A. But it could still play a role in fluctuations in the mystery of the larger star, the researchers said.
“The binary companion can influence the long-term evolution of the system,” they wrote in their paper.
Scientists have previously discovered that widely spaced binary stars can be pushed by larger gravitational forces to move very close to the reciprocal center of mass several times over about 10 billion years.
In turn, this could lead to the disruption of planets and other small bodies in orbit where they are stretched and torn by gravitational interactions, resulting in clouds of debris.
The scenario is yet to be confirmed. At such a wide separation, the two stars would have an extremely long orbit, and the observations made were not enough to characterize this orbit. KIC 8462852 B could be a star that has been evacuated from the system; or the two stars could be members of a moving group.
Researchers believe that a binary is the most likely explanation for measuring the two stars, but future measurements of the pair will be needed to better understand their relationship. This may help to confirm or rule out the role of KIC 8462852 B in the irregular brightness of the star.
But for all the mystery lovers out there, never be afraid. There are other strangely blurred stars, including a star for which the binary company has already been considered and a tempting collection of 21 stars that could be even stranger.
The team’s research was accepted The astrophysics journaland is available on arXiv.