Betelgeuse, the star, pronounced like the Halloween occult classic Beetlejuice, forms the left shoulder in the constellation Orion and sits around 650 light-years from Earth but remains one of the brightest stars visible with the naked eye. As a red giant star, an early stage of star death that’s ushered in when a star runs out of hydrogen fuel at its core, Betelgeuse has been expanding and pulsating as researchers have watched the orange celestial being approach instability, otherwise known as star explosion into a supernova. Betelgeuse pulsation has previously been attributed to variability as a star that periodically grows and shrinks over time, but a recent study reveals the star’s light curve, a record of pulsation rhythm, doesn’t match up with its radial velocity or rate of expansion. Researchers hypothesize that this missing beat, or difference in the star’s radial velocity and light curve, indicates that a Betelgeuse has a companion star that is the culprit of this “out-of-syncness.”
The star’s march to death has been marked by a brilliant orange glow, as the star has expanded to just under eight times the Sun’s mass, that has been pulsating energy over the span of 400 days in intervals of brightening and dimming periods. The star’s 400-day heartbeat is nestled into a six-year-long larger, slower beating called a long secondary period (LSP) that approaches dimming and brightening. Analysis of the light curve reveals that the star’s phases of brightness are not correlated to phases of radial expansion, which supports the hypothesis that a second smaller star may be contributing to Betelgues’s variability in shine. As heartbeats are nestled within heartbeats, the old red supergiant may have a “Betelbuddy” that drives an irregular variability and pulsation previously overlooked.
Astronomers studying the pulsating discrepancy report, “The light curve-radial velocity phase difference requires a companion to be behind Betelgeuse at the long secondary period luminosity minimum.” Pulling from the raw data of radial velocity phase not lining up with the phases of brightness and dimming, the authors summarize that Betelguese is brightest when the red supergiant star and it’s hypothetical companion star, estimated to be about 1.7 times the mass of our sun, shine together and create a stronger pulsation from our perspective on earth.
The dust holds the answers. In 2020, Betelguese’s 400-day-long heartbeats unexpectedly dimmed beyond their previous dimmest shine, termed the Great Dimming, which has cut the heartbeat intervals in half and excited an extra phase of brightening that invited extra attention from researchers. Despite speculation that the red supergiant was approaching a final explosion of death, the Great Dimming was traced to a large expulsion of material from the star’s interior that created a dust cloud that then obscured Earth’s view of the star. In other words, Betlegeuse’s shine was shrouded in a star fart which triggered the researcher’s interest in the subtle role dust plays in the big-picture pulsation of the LSP.
So, how does the companion star play a role? Betelgeuse is a misunderstood star if anything, and recent discrepancies in the star’s pulsation and expansion have rewritten Betelguese’s prognosis away from star death. The long-anticipated supernova explosion that would outshine all observed star deaths in 400 years has been replaced with a new interest in the interaction between the possible companion star and its influence on the celestial heartbeat that iconized Betelgeuse. If Betelguese’s brightening phases aren’t associated with expansion, what dictates the intervals of dimming and brightening? The team that investigated the missing beat between the star’s radial velocity and light curve can only propose a firm theory that Betelguese’s companion star functions to disperse the clouds surrounding Betelguese that cause periodic dimmings as Betelbuddy orbits into Earth’s view and restores the red supergiant’s luminance. Ultimately, the team suggests that the Betelgeuse we’ve come to know is a binary star system as its heartbeat suggests a buddy star of an unknown classification that plows through years of dust, like a good seasonal cleaning.
