A once in a century astronomical event took placed on in the evening of December 11, when the bright red star Betelgeuse briefly winked out of the night sky for a few seconds. It wasn’t the talked about great dimming that is expected to preclude the explosive supernova ending of this red supergiant. It was caused by passing asteroid Leona. This is a rare and exciting opportunity for scientists to observe both objects in detail, as well as to test our knowledge of their sizes, shapes and orbits.

We are all used to eclipses, when the Moon or Earth occults the other heavenly body and passes in the shadows. Asteroid-star occultations are actually very common, about half a dozen happen every day. However being able to observe one to the naked eye is extremely rare.

Betelgeuse is one of the largest and most luminous stars in the sky, located about 650 light-years away in the constellation of Orion. It is a red supergiant, if it were placed at the center of our solar system, it would engulf the orbits of Mercury, Venus, Earth and Mars. It is also a variable star, changing its brightness and color over time due to pulsations, convection and dust formation.

Asteroid Leona is a much smaller and fainter object, orbiting the Sun between Mars and Jupiter and originated from the outer asteroid belt. Leona is about 66 kilometers in diameter and has an irregular shape, but just large enough to block out a bright star such as Betelgeuse. Leona is a dark reddish high carbon asteroid making it a challenge to observe even with an amateur telescope at a magnitude 14 brightness, so only large telescopes will be able to capture the momentary dimming.

The occultation of Betelgeuse by Leona was visible from a narrow path across the Earth, stretching from southern Europe, Turkey, Greece, Italy, the tip of Florida and Mexico. The occultation is expected reduce the brightness by 3 magnitudes, making it disappear to the naked eye.

The occultation of Betelgeuse by Leona is a rare and valuable opportunity for both amateur and professional astronomers. It will allow us to measure the diameters and shapes of both objects with unprecedented precision, as well as to study their atmospheres and surfaces. It will also help us to refine our models of their orbits and motions, which are affected by various factors such as gravity, radiation pressure and thermal effects. Moreover, to the lucky few it was a sight that will not be repeated for many years to come.