What is a ‘lunar occultation?' How, when to see the celestial event, visible in Chicago this week

The Moon will pass in front of a bright star Thursday evening

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Stargazers in many parts of the country including the Chicago area this week will have the chance to witness an astronomical event called "lunar occultation," according to the Adler Planetarium.

Similar to an eclipse, a "lunar occultation," Adler says, is when the Moon passes in front of a star or planet. Last year in December, a rare lunar occultation occurred, when Mars disappeared behind the Moon, and then reappeared near the Moon's opposite edge.

According to experts, such a sighting is not expected to happen again until 2025.

While this week's spectacle may not be as rare, it is still expected to be visible in the Chicago area.

The event will occur in the evening on Thursday, Aug. 24, "when the first-quarter Moon passes in front of the first-magnitude star Antares, in the zodiac constellation Scorpius," a blog post from Planetarium said.

"The star is expected to disappear behind the dark edge of the Moon just before 9:30 p.m.," the post continued. "Both the Moon and Antares are only about 15 degrees above the south-southwest horizon at the start of the occultation."

According to Adler, stargazers shortly after 10:30 p.m. who take a close look at the horizon should see Antares reappear from the bright side of the Moon.

However, the city's skyline could complicate things, Adler said.

"Antares’ reappearance may not be easily visible in the Chicago area due to the general brightness of the local night sky and because nearby trees and buildings might obscure your view."

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