The moon will appear to โswallowโ the bright star Regulus on May 23 in a rare celestial event visible across parts of the Pacific. (Image credit: Background: Alan Dyer/VWPics/Universal Images Group via Getty Images. Moon image: NASA Scientific Visualization Studio. Created by Anthony Wood in Canva.)
Skywatchers across parts of the Pacific will witness a spectacle that can feel almost impossible at first glance as the moon glides across the night sky on May 23. On that particular evening, the moon will appear to swallow one of the brightest stars in the constellation Leo.
The event, known as a lunar occultation, will briefly hide Lunar occultation star Regulus from view as the moon passes directly in front of it. For several minutes, the starโs blue-white light will vanish behind the lunar disk before reappearing on the other side.
But not everyone on Earth will see the disappearance. That is because the moon, unlike distant stars, is close enough to Earth for a phenomenon called parallax to dramatically alter the view depending on where an observer stands on the planet. At an average distance of about 238,855 miles (384,400 kilometers), the moonโs apparent position in the sky can shift by as much as 2 degrees from one location to another โ enough to determine whether Regulus vanishes behind the moon or merely appears to skim past it.
Astronomers say the full occultation will be visible primarily across the Pacific, including parts of Fiji, Samoa and Tonga, where observers will see the darkened edge of the half-lit moon move silently across the star in the early hours before dawn.
In Sydney, the encounter will unfold differently. There, Regulus will appear to graze the moonโs upper edge after sunset, hugging the bright lunar rim before slipping below the horizon shortly before midnight.
Across the United States, viewers will not see the actual occultation, but the pairing will still create one of the more striking naked-eye sky alignments of the season. Overnight on May 22 into May 23, the moon and Regulus will drift to within roughly 1 degree of each other โ about the width of a little finger held at armโs length.
Regulus, sometimes called the โHeart of the Lion,โ has fascinated skywatchers for thousands of years. The star, located about 79 light-years from Earth, is among the brightest stars visible in the night sky and has long been associated with royalty and power in ancient cultures.
The celestial alignment also offers a reminder of how dynamic the night sky truly is. Though stars can appear fixed and eternal, the moonโs rapid orbit around Earth constantly reshapes what humans see overhead from hour to hour โ and from continent to continent.
For those unable to witness the occultation directly, astronomy apps like Stellarium and SkySafari 7 Pro can simulate the event from virtually any location on Earth, allowing users to watch the moonโs slow-motion eclipse of Regulus unfold in real time.
About The Author
