Betelgeuse's Brightness Cycles Include a 2,100-Day Pattern

Betelgeuse, a variable red supergiant in Orion, shows a regular brightness variation linked to pulsation. The reported pulsation cycle lasts about 430 days, while a second, longer cycle spans about 2,100 days.

Key details

• Betelgeuse’s regular pulsation cycle lasts approximately 430 days.
• The star’s longer secondary brightness cycle lasts about 2,100 days, or 5.75 years.
• Observations published in January 2026 reported a faint possible companion, Alpha Ori B, which may orbit Betelgeuse roughly every six years.
• The proposed companion has also been informally called “Betelbuddy” and “Siwarha.”

Betelgeuse’s secondary brightness cycle lasts about 2,100 days, or 5.75 years.

Why it matters

A possible companion could give astronomers another way to study Betelgeuse’s longer-term brightness changes. The proposed explanation is that the companion may create a denser wake in surrounding material, with dust along the line of sight dimming the star. That explanation remains unconfirmed.