Betelgeuse has faded in recent months, renewing questions about the changing brightness of one of the night sky’s most prominent stars. Astronomers point to several possible contributors: the star’s regular expansion and contraction, clouds of dust, and a probable companion orbiting nearby.

The red supergiant has a pulsation cycle of about 430 days. As it expands, its outer layers cool and the star dims; as it contracts, they heat up and it brightens. Betelgeuse also shows a longer dimming cycle of roughly 2,100 days, or 5.75 years, which had puzzled astronomers for decades.

In January 2026, researchers using the European Southern Observatory’s Very Large Telescope and NASA’s Hubble Space Telescope reported direct evidence of a faint companion, formally named Alpha Ori B and called Siwarha. The companion is thought to orbit within Betelgeuse’s outer atmosphere about once every six years. Its movement through surrounding gas and dust may create a dense wake that affects the material flowing away from the star. If dust in that wake passes between Earth and Betelgeuse, it could make the supergiant appear dimmer.

Betelgeuse has recently dropped from magnitude +0.5 to +0.95, leaving it slightly fainter than Aldebaran, the orange star in Taurus. The change may fit the dimming pattern associated with the companion, but brightness alone does not establish its cause.

The current decline is distinct from the much more dramatic Great Dimming of 2019–2020, when Betelgeuse lost more than two-thirds of its apparent brightness. Researchers attributed that event to a large eruption of hot plasma from the star. The expelled material cooled and formed silicon monoxide dust, which blocked some of the star’s light from Earth. The eruption coincided with a low point in the 430-day pulsation cycle and may also have been affected by Siwarha.

Betelgeuse later brightened, reaching magnitude 0.0 in spring 2023. Although the Great Dimming prompted speculation that the star was about to explode, the source reports that observations showed no significant change in its luminosity and that it remains in its helium-burning phase. Its varying brightness, therefore, does not have to come from a single process: pulsations, dust and the possible companion may each help explain different changes.

Sources: Space.com.