Dec. 10, 2023: (Spaceweather.com) For years, astronomers have worried that Betelgeuse might explode. Instead, it’s about to disappear. On Dec. 11th (USA) and 12th (Europe), main belt asteroid Leona will pass directly in front of Betelgeuse, a first-magnitude star in the shoulder of Orion. Millions of people in a narrow path stretching from South Florida to Italy and Greece can look up and see the red giant dim or even vanish.

Google Earth: Click to view an interactive map of the occultation path

“This represents an extraordinary and unique opportunity to analyze the diameter and brightness distribution of Betelgeuse with extreme angular resolution,” says astronomer J. L. Ortiz of the Instituto de Astrofísica de Andalucía, lead author of a newly-released preprint about the occultation.

Betelgeuse is not a typical star. Its diameter is 760 times the sun’s, so it appears as a disk 40 milliarcseconds across the sky, much larger than most other stars. High resolution images of Betelgeuse seem to reveal a star in turmoil with giant convection cells bubbling up to the surface. The passage of the asteroid across Betelgeuse may allow astronomers to map these cells and evaluate their role in a possible future supernova explosion.

Above: Images of Betelgeuse taken by the European Southern Observatory’s Very Large Telescope

Much is unknown about this occultation. The shape of the asteroid itself is an X-factor. In Sept. 2023, Ortiz and colleagues watched the asteroid occult another star from 17 different locations on Earth. They found that Leona has an oblong shape with dimensions 80 x 55 km, whereas most predictions of the occultation assume the asteroid to be spherical. Leona’s odd shape, plus the fact that it is rotating, could produce some surprises. The occultation path may be wider than expected, and there could be interesting “partial eclipse” effects visible even near the center of the path.

There are huge population centers in the occultation path, especially in south Florida where Leona’s shadow crosses Miami and Fort Lauderdale. For observers there, Betelgeuse will wink out for about 10 seconds on the evening of Dec. 11th just before 8:25 pm Eastern Standard Time. In Europe, the occultation happens on Dec. 12th between 1:10 UT and 1:16 UT. To find out when to look from your location, we recommend downloading this excellent Google Earth file; when viewing the map, click on the little dots for occultation times.

Amateur astronomers who wish to collect research quality light curves are encouraged to read these observing tips from the International Occultation Timing Association. For casual naked-eye observers, here’s a simple sky map.