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Tuesday, December 1, 2015

Sky Tonight—March 17, Moon swings close to Leo’s bright star Regulus

Courtesy of EarthSky
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Can you find the star that is shining close to the big and bright waxing gibbous moon tonight? That is Regulus; the brightest star in the constellation Leo the Lion. Regulus is the only first-magnitude star to sit almost exactly on the ecliptic.

The ecliptic is the Earth’s orbital plane projected outward onto the sphere of stars. The ecliptic is often shown on sky charts, because the moon and planets are always found on or near the ecliptic.

Four first-magnitude stars reside close enough to the ecliptic to be occulted – covered over – by the moon on occasion: Regulus, Spica, Antares, and Aldebaran. In fact, the moon last occulted Antares during January and February of 2010. Although no more lunar occultations of first-magnitude stars are in the works for 2011, lunar occultations of bright stars are not uncommon.

Where is the ecliptic in relation to the Milky Way?

However, an occultation of a first-magnitude star by a planet is extremely rare. The last time a planet occulted a first-magnitude star was when Venus occulted Regulus on July 7, 1959. The next time will be when Venus occults Regulus on October 1, 2044.

Before 1959, the most recent planet/first-magnitude star occultation took place on November 10, 1783, when Venus occulted Spica. Venus will again occult Spica on September 2, 2197.

Tonight, on Thursday, March 17, the moon shines close to Leo’s brightest star, Regulus, the only first-magnitude star to sit almost exactly on the ecliptic.

Regulus: Lion Heart

Antares: Heart of the Scorpion

By Bruce McClure

Astronomy Picture of the Day from NASA/JPL

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U.S. Naval Observator Astronomical Information center

Universe Today

StarDate Online

Sky and Telescope

National Geographic

Space Com

Simostronomy Blog

Amazing Space

The York County Astronomical Society

Scope City

James S McDonnell Planetarium

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