Astronomers have found the strongest evidence yet for the existence of a companion star orbiting Betelgeuse, the red supergiant marking Orion’s shoulder. The discovery isn’t based on direct imaging alone, but on a distinct “wake” the smaller star leaves in Betelgeuse’s enormous atmosphere—much like a boat churning water behind it.
The Mystery of Betelgeuse’s Cycles
For centuries, Betelgeuse has displayed periodic fluctuations in brightness. Astronomers observed two primary cycles: a shorter one (roughly 400 days) caused by the star’s natural pulsations, and a longer, unexplained cycle lasting around 2,100 days.
The long cycle has been a puzzle for decades. Previous attempts to confirm a companion star were suggestive but not conclusive.
In 2024, researchers proposed that this longer cycle was driven by an orbiting companion roughly the size of our sun. A fuzzy image of the suspected companion emerged in 2025, but skepticism remained.
Wake Confirms Companion’s Existence
Astrophysicist Andrea Dupree and her team used eight years of data from the Hubble Space Telescope and ground-based observatories to search for direct evidence of the companion’s influence on Betelgeuse’s atmosphere. The companion orbits extremely close, at about four times the Earth-Sun distance, well within Betelgeuse’s vast outer layers.
This proximity suggests the smaller star would carve a path through the surrounding gas. Dupree’s team found that specific wavelengths of light brighten as the companion passes in front of Betelgeuse, then dim as it moves behind—consistent with an expanding gas trail, or wake.
Implications for Stellar Evolution
The confirmation of Betelgeuse’s companion is significant. It suggests that binary systems may be more common among red supergiants than previously thought. Stellar astrophysicist Anna O’Grady of Carnegie Mellon University called Dupree’s findings “very convincing.”
Betelgeuse is currently eclipsing the companion, but astronomers plan to observe it again when it reappears in 2027. Dupree also intends to study other supergiants with similar periodic behavior to see if they, too, harbor unseen companions. The discovery of these stellar companions could reshape our understanding of how massive stars evolve.
