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Moon, Regulus and Jupiter February 21

Tonight – February 21, 2016 – the full-looking waxing gibbous moon closely partners with Regulus, the brightest star in the constellation Leo the Lion. There’s an even brighter starlike object beneath the moon and Regulus by early-to-mid evening. It’s not a star, but the blazing planet Jupiter, now only a few weeks away from its annual opposition on March 8, 2016, at which juncture the king planet will come closest to Earth for the year. From North America, the moon shines closer to Regulus than it does in Africa, Europe and Asia. Nonetheless, you’ll find Regulus in the moon’s vicinity tonight. These luminaries are above your eastern horizon at early evening. They climb highest up for the night at roughly midnight local time and sit low in the west as darkness gives way to dawn on February 22.

The moon turns full on February 22, at 18:20 Universal Time. At our U.S. times zones, that translates to 1:20 p.m. EST, 12:20 p.m. CST, 11:20 a.m. MST and 10:20 a.m. PST. In North America, we won’t see the February full moon at the instant it turns full. That’s because the moon turns full during our daylight hours, when the moon is still under the horizon and beneath our feet. Even so, we’ll see a full-looking waxing gibbous moon on the night of February 21-22 and a full-looking waning gibbous moon on the night of February 22-23.

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.

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Regulus is the brightest star in Leo the Lion. Here’s how to find Leo anytime. 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.

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 revolves 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!

Starting on December 18, 2016, a series of monthly lunar occultations of Regulus will take place until the series’ conclusion on April 24, 2018.

Bottom line: Enjoy the pairing of the waxing gibbous moon and star Regulus on February 21, 2016! The blazing planet Jupiter – nearly at its best for this year – follows the moon and Regulus by early-to-mid evening.

Live by the moon with your 2016 EarthSky lunar calendar!

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Bruce McClure