Since its discovery a few years ago, Boyajian’s star has been a fascinating mystery. The star experiences dimming events that astronomers still can't explain. An off-the-cuff remark about this being "caused by aliens" led to popular media stardom as the “Alien Megastructure” star.
Sadly, aliens have not been found around this star, but astronomers have found mounting evidence of something else. Boyajian’s star, discovered by Dr Tabetha Boyajian, appears to have a companion, KIC 8462852 B, as detailed in a paper accepted for publication in The Astrophysical Journal. This fellow star was known about from the very first observations but now researchers have collected enough data to claim this is a binary system, a system where two astronomical bodies are so close their gravitational pull causes them to orbit each other.
The data the researchers collected shows that the two stars are moving in the same direction and by the same amount. The probability that they are just two random stars doing that is extremely low, though the team points out they have not yet been able to prove that they are gravitationally bound.
If they are, the companion is located 132 billion kilometers (82 billion miles) from Boyajian’s star. That’s 880 times the distance between Earth and the Sun. At this distance, the researchers don’t expect the companion to have a direct influence on the mysterious dimming of the star but it might perturb the orbits of closer objects, and so contribute to the unexplained phenomena.
“Although it has not been thought to be a likely explanation for Boyajian’s Star A’s light curve, it is a potential source of instability in the long-term evolution of the system and could excite chaotic orbits of objects in the system," the author wrote in the study. "Efforts to explain KIC 8462852 A’s dimming events should be informed by the existence of a wide stellar binary companion to the system.”
Stars orbited by planets can experience a drop in brightness by at most 1 percent of their light. We have found many planets in this way, as the light from a star dips as a planet crosses in front of it. But these are mere flickers compared to what Boyajian’s star has experienced. The star had two major light dips, one where its light was at 15 percent reduction and one where its brightness dropped by 22 percent.
The star has seen other light dips, some reaching 11 percent, many just a few percent, but none as profound as those two. On top of that, the star's total brightness is declining over the years, which could be completely unrelated to the dips. Similar dips have been seen on another puzzling completely different star.
More observations will hopefully help us understand if the second star is indeed a companion and what possible effect it might have on Boyajian’s star and its mysterious dimming.
[H/T: Science Alert]