Free Astronomy Magazine September-October 2025

47 ASTRO PUBLISHING Dimming.’ The event led some to believe that a supernova death was quickly approach- ing, but scientists were able to determine the dimming was actually caused by a large cloud of dust ejected from Betelgeuse. The Great Dimming mystery was solved, but the event sparked a renewed in- terest in studying Betel- geuse, which brought about new analyses of archival data on the star. One analysis led scientists to propose that the cause of Betel- geuse’s six-year vari- ability is the presence of a compan- ion star. But when the Hubble Space Telescope and the Chandra X-Ray Observatory searched for this com- panion, no detections were made. U sing the NASA-NSF-funded ‘Alopeke instrument on the Gemini North telescope, astrono- mers have discovered a companion star in an incredibly tight orbit around Betelgeuse. This discovery answers the millennia-old question of why this famous star experiences a roughly six-year-long periodic change in its brightness, and pro- vides insight into the physical mechanisms behind other variable red supergiants. The companion star appears blue here because, based on the team’s analysis, it is likely an A- or B-type star, both of which are blue-white due to their high temperatures. [International Gemini Observatory/NOIRLab/NSF/ AURA − Image Processing: M. Za- mani (NSF NOIRLab)] T he International Gemini Observatory consists of twin 8.1-meter diameter optical/infrared telescopes located on two of the best observing sites on the planet. The North telescope is lo- cated on Hawaii’s Maunakea. [International Gemini Observatory/NOIRLab/NSF/AURA/J. Chu] The companion star has now been detected for the first time by a team of astrophysicists led by Steve How- ell, senior research scientist at NASA Ames Research Center and lead au- thor of the paper reporting the dis- covery. They observed Betelgeuse using a speckle imager called ‘Alopeke. ‘Alopeke, which means ‘fox’ in Hawaiian, is funded by the NASA–NSF Exoplanet Observational Research Program (NN-EXPLORE) and is mounted on the Gemini North telescope, one half of the In- ternational Gemini Observatory, funded in part by the U.S. National Science Foundation and operated by NSF NOIRLab. Speckle imaging is an astronomical imaging technique that uses very short exposure times to freeze out the distortions in images caused by Earth’s atmosphere. This technique enables high resolution, which, when combined with the light col- lecting power of Gemini North’s 8.1-meter mirror, allowed for Betel- geuse’s faint companion to be di- rectly detected. Analysis of the companion star’s light allowed Howell and his team to determine the companion star’s characteristics. They found that it is six magnitudes fainter than Betel- geuse in the optical wavelength range, it has an estimated mass of