Skywatchers across parts of the Pacific will see the moon pass in front of the bright star Regulus on May 23, temporarily blocking its light in a celestial event known as a lunar occultation. Elsewhere, viewers will watch the star pass extremely close to the lunar disk as the pair drift through the constellation Leo.
Why can’t everyone see the moon occult Regulus?
The moon orbits Earth at an average distance of just 238,855 miles (384,400 kilometers), close enough for an effect called “parallax viewing” to occur, where an object appears to be in a subtly different position against its backdrop based on where you view it from. The parallax effect can cause the moon’s position to vary by as much as 2 degrees depending on where you are on Earth, according to NASA.
Who will see the moon occult Regulus?
Stargazers in Fiji, Samoa, Tonga and a host of other Pacific island nations will see the shadowed side of the half-lit moon pass in front of Regulus during the early hours of May 23, blocking its light entirely, according to the astronomy guide In-The-Sky.
From Sydney, Australia, the blue-white light of Regulus will appear to graze the top of the lunar disk after sunset, before skirting around its sunlit side to set beneath the moon shortly before midnight.
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U.S. viewers will get their best view of the cosmic duo overnight on May 22-23, as the moon advances towards Regulus through the late-spring sky. The moon and Regulus will be separated by roughly 1 degree, about the width of your little finger held at arm’s length, by the time they set on the western horizon in the early hours of May 23, though the occultation itself won’t be visible.
Don’t forget, you can simulate exactly what the occultation will look like from your location by using a smartphone astronomy app, such as Stellarium or Sky Safari 7 Pro.
Editor’s Note: If you capture an image of the moon with Regulus and want to share it with Space.com’s readers, then please send your photo(s), comments, and your name and location to spacephotos@space.com.