An Asteroid Will Eclipse a Red Star in the Constellation Orion Monday Night

In the U.S., the rare event will only be visible from southern Florida, but it will be livestreamed from Italy for viewers everywhere

Stars in the sky above trees on a snowy ground
The consellation Orion and other stars in the sky in Alberta, Canada, in 2019. Alan Dyer / VW PICS / Universal Images Group via Getty Images

For a few seconds on Monday night, star gazers in certain parts of the world will be able to watch an asteroid block their view of the star Betelgeuse, which brightly shines red in the constellation Orion.

The event, called an occultation, will take place at around 8:17 p.m. Eastern time on the evening of Monday, December 11, according to Sky & Telescope’s Jan Hattenbach.

People in a narrow band from Mexico and southern Florida to southern Europe and Eurasia will be able to watch the occultation, per’s Brett Tingley. Outside of Mexico and the southern U.S., the event will also be visible from parts of Afghanistan, Albania, Armenia, Azerbaijan, the Bahamas, China, Greece, Iran, Italy, Portugal, Spain, Tajikistan, Turkey, Turkmenistan and Uzbekistan.

But for those who are not located in these areas, Italy’s Virtual Telescope Project will be livestreaming the occultation Monday night, starting at 8:00 p.m. Eastern time.

Betelgeuse is a red supergiant star that glows orange-red in the sky. Humans have assigned it the role of Orion’s right shoulder (appearing on Orion’s left side from Earth), according to NASA. It’s around 700 light-years from our planet and is particularly bright—at about 7,500 to 14,000 times brighter than our sun, it’s often the tenth-brightest star visible to us. It also dwarfs our sun in size, measuring more than 700 times its diameter and around 15 times its mass.

On a cosmic scale, Betelgeuse is only a baby—the star is around ten million years old, while our sun has lived that long 460 times over. But most of Betelgeuse’s lifespan has already passed—it’s burning quickly through its materials and astronomers expect it will explode in a violent supernova in around 100,000 years.

On Monday night, Betelgeuse will be temporarily blocked by the asteroid 319 Leona, according to the Virtual Telescope Project. Leona is in the main asteroid belt between Mars and Jupiter, and observations of a recent eclipse suggest it’s about 34 miles wide and 50 miles long, per Marcia Dunn of the Associated Press (AP).

Exactly how long the occultation lasts will depend on the size of the star and asteroid, which are not precisely known. But the whole event should only be for a few seconds. The asteroid could block the whole star, or the outer border of the star could still be visible, creating a “ring of fire” around the asteroid’s silhouette, per the AP.

“Which scenario we will see is uncertain, making the event even more intriguing,” Gianluca Masa, an astronomer and founder of the Virtual Telescope Project, tells the AP. An occultation of a star of Betelgeuse’s brightness can be seen from Earth only every few decades, per Sky & Telescope.

The event will allow researchers to better understand both the asteroid and the star. They’ll learn more about the shape of Leona, as well as the convective regions on Betelgeuse that lead to its changing brightness, per the Virtual Telescope Project.

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