Free Astronomy Magazine September-October 2020

SEPTEMBER-OCTOBER 2020 unusual was happening. The star contin- ued to dim even into January of this year, ending the month at +1.62 − the same magnitude as Bellatrix, which is usually the third brightest star in Orion (Betelgeuse and Rigel alternate for first and second place). In practice, in just over four months, Betelgeuse had lost one magnitude, be- coming 2.5 times less bright. At the same time, its surface temperature dropped by 100-200 degrees, an unusual phenomenon for a star its size. In the ab- sence of extraordinary photospheric phe- nomenologies, only an 8% reduction in stellar diameter could have account for a similar variation, yet a reduction of that magnitude would have been inexplicable. The first interpretations of Betelgeuse’s strange photometric behavior began to circulate as early as last December. Among the most accredited, there were: the over- lap of the minimums of the three known I f it were located at the center of our solar system, Betelgeuse would perhaps incorpo- rate Jupiter and destabilize the orbit of Saturn. [ALMA(ESO/NAOJ/ NRAO)/E. O’Gor- man/P. Kervella]