Three planets are sliding behind the moon in a lunar occultation

The New York Times

The moon is playing a game of planetary peek-aboo as it momentarily blocks Venus, then Mars and then Mercury in the sky. Although it is difficult to see this disappearing act in much of the world, it’s a vivid reminder of the cosmic clockwork at play in our solar system.

The event is called a lunar occultation, and it occurs whenever the moon passes in front of a faraway celestial object. The duration of a lunar occultation depends on many factors, like what is getting blocked and where on Earth someone is observing it from. Solar eclipses, like the one that mesmerized the nation last month, are examples of the moon occulting the sun.

When you’re in the right place, with the right viewing equipment, lunar occultations can be quite breathtaking, like the one that occurred in 2007 when the moon occulted Saturn.

The last time the moon slid past three planets within 24 hours as it is this week was on March 5, 2008 (when it was Mercury, Venus and Neptune), and the next time will be in 2036, according to EarthSky. During this year’s event, as a bonus, the moon is also interrupting the light from Regulus, the brightest star in the constellation Leo, a few hours after it passes Venus.

“It’s almost like it’s a dance in the sky,” said Jackie Faherty, an astrophysicist at the American Museum of Natural History.

According to Universe Today, the lunar occultation was set to occur from Sunday evening through Monday evening in the Eastern time zone.

But be aware that only certain parts of the world can see particular occultations. And to make it even tougher, the occultations are happening during daytime hours. If you’re in one of the locations that will see an occultation, you’re most likely to catch it witha small telescope.

Here are the best places to see the lunar occultations, according to the International Occultation Timing Association.

• Venus will be most visible in Australia, New Zealand and parts of the Southeast Pacific. But because Venus is very bright, it is still visible during the daytime without a telescope.

• Regulus will be most visible in India, the Middle East and parts of Southeast Asia.

• Mars will be most visible in Hawaii and parts of Mexico.

• Mercury will be most visible over parts of the Pacific Ocean.

As a consolation for those in North America who won’t be able to see the occultations, you can still try to catch a celestial alignment among Mercury, Mars, Regulus and Venus, in that order, before sunrise.

The moon and Venus are brightest and easiest to see. Regulus will be a bit below Venus. Mercury and Mars will be the toughest to spot since they are very near the horizon. Though it will be tricky to pull off, if you wake up early, you’ll see a planetary parade featuring the moon and the heart of a lion.

Even if you have no shot at spotting this event, consider how useful occultations can be for scientific study of our solar system. According to NASA, its Kuiper Airborne Observatory discovered that Uranus had faint rings when it passed in front of a distant star in 1977.