The moon and Regulus, the brightest star in the constellation Leo the Lion, transit – climb highest up for the night – during the wee hours after midnight. A few hours thereafter, ruddy Mars transits – reaches its highest point – at roughly 4:00 a.m. You may want to consult an astronomical almanac because the precise rising/transit times of these heavenly bodies depend on your latitude and location within your time zone.

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Looking from south to west in the predawn sky on January 12.

As the predawn sky starts to give way to dawn tomorrow, you’ll see Mars following the moon and Regulus downward in the western sky. At this time, the ringed planet Saturn and Spica, the constellation Virgo’s brightest star, reach their high point in the southern sky. On our chart, we show the ecliptic – Earth’s orbital plane projected onto the stellar sphere – because the planets are always found on or near this imaginary circle on the sky’s dome.

Where is the ecliptic in relation to the Milky Way?

Mars isn’t really chasing the moon and Regulus across the sky tonight. The red planet, the moon and Regulus all parade westward for the same reason that the sun goes westward during the day. The Earth rotates from west-to-east on its axis once a day, making it seem as if the sun, moon, planets and stars move westward while the Earth stands still.

Although we show the constellation Leo on tonight’s chart, you may not see much more than the star Regulus and the planet Mars in the glare of tonight’s big and bright waning gibbous moon.

Article source: http://earthsky.org/tonight/mars-chases-moon-regulus-across-sky-on-night-of-january-11