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Moon chases Regulus all night long on night of February 15


Tonight for February 15, 2014

An imaginary line drawn between the pointer stars in the Big Dipper - the two outer stars in the Dipper's bowl - points in one direction toward Polaris, the North Star, and in the opposite direction toward Leo.

On the night of February 15, 2014, the full-looking waning gibbous moon follows Regulus, the brightest star in the constellation Leo the Lion, across the sky all night long. The two celestial luminaries are found in the east at nightfall and early evening. They climb highest up for the night around midnight and sit low in the west as darkness gives way to dawn.

Regulus is the Lion’s Heart

The moon and Regulus go westward during the night for the same reason that the sun travels westward across the sky during the day. The Earth rotates from west-to-east on its axis, making it appear as if the sun, moon, planets and stars move westward across the sky while the Earth stays still.

Big and Little Dippers: Everything you need to know

In fact, the moon’s orbital direction is actually eastward (toward sunrise). Note the moon’s position relative to Regulus tonight. Then note its position relative to Regulus tomorrow night – or 24 hours later. The moon’s change of position in front of the background stars lets you know how far the moon has revolved around our planet Earth in one day.

Regulus is well known for its extremely fast rotation rate. Our sun takes nearly four weeks to complete one rotation. In contrast, Regulus rotates one time in only 16 hours. This star has an equatorial diameter that’s 4.3 times greater than the sun’s but it still rotates at 700,000 miles (1,100,000 kilometers) per hour. At that speed, you could reach the moon in a little over twenty minutes!

Path where asteroid 163 Erigone occulted Regulus on March 20, 2014. Click here for a larger map Image credit: Aldo Vitaliano

Because I live in New York, I am well aware of the prediction of asteroid 163 Erigone occulting Regulus on March 20, 2014. You won’t see the asteroid but you will see Regulus disappear behind it, if you’re in the right spot. Best yet, you need no optical aid. This occultation will happen along a very narrow strip from Bermuda, New York City to Oswego in New York, and northward through Canada to North Bay, Ontario. The asteroid will occult (cover over) Regulus in New York State sometime between 2:06 to 2:08 a.m. EDT on March 20, 2014, for a maximum of 14 seconds. Click here for more information.

Starting on December 18, 2016, a series of monthly lunar occultations of Regulus will take place until the series’ conclusion on April 24, 2018. In the meantime, enjoy the pairing of the waxing gibbous moon and Regulus on this Saturday night!