Moon and Regulus early evening to dawn

Tonight – February 11, 2017 – the full-looking moon closely partners with Regulus, the brightest star in the constellation Leo the Lion. They climb highest up for the night at roughly 1 a.m. local time and sit low in the west as darkness gives way to dawn on February 12.

The moon turned full on February 11 at 00:33 Universal Time. At our U.S. times zones, that translated to February 10 at 7:33 p.m. EST, 6:33 p.m. CST, 5:33 p.m. MST and 4:33 m.m. PST. In North America, the moon will probably look full to the eye, although it is technically a waning gibbous moon.

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 spins from west-to-east on its rotational axis, making it appear as if the sun, moon, planets and stars move westward across the sky while the Earth stays still.

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, of course, it’s the Earth that’s spinning, causing that westward shift, and, meanwhile, the moon’s orbital direction is always eastward, or toward the sunrise direction, in our sky.

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.

The moon takes several days to pass entirely in front of the constellation Leo the Lion. The green line depicts the ecliptic – Earth’s orbital plane projected onto the constellations of the zodiac.

Regulus is well known for its extremely fast rate of spin. Our sun takes nearly four weeks to complete one complete spin on its axis. In contrast, Regulus around once every 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 km) per hour. At that speed, you could reach the moon in a little over 20 minutes!

A series of monthly lunar occultations of Regulus started on December 18, 2016, and will continue to take place until the series’ conclusion on April 24, 2018. The February 11, 2017 occultation of Regulus appears in the sky from Australia, Wilkes Land, and New Zealand.

Bottom line: Enjoy the pairing of the waning gibbous moon and Regulus – brightest star in Leo the Lion – on February 11, 2017!

Live by the moon with your 2017 EarthSky lunar calendar!

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