On these next few evenings, the waxing gibbous moon is moving through the prominent constellation Leo the Lion. In particular, watch for the moon on May 1, 2020, when it’ll shine near the bright star Regulus, representing the Lion’s Heart.
The dark side of a waxing moon always points in the moon’s direction of travel relative to the backdrop stars of the zodiac. Although – on any given night – the moon will move westward because of the Earth’s rotation, the moon’s orbital motion will actually cause the moon to travel eastward from day to day. The moon moves 1/2 degree (its own diameter) eastward per hour in front of the constellations of the zodiac – or about 13 degrees eastward per day.
Note where the moon appears relative to Regulus at nightfall May 1 and then again as darkness falls on May 2. The change in the moon’s position in front of Leo will be obvious.
Want to know the moon’s position in front of the constellations of the zodiac? Visit Heavens-Above.
By May 3, the moon will have moved again on your starry dome, as it pursues its endless orbit around Earth. On May 3, the moon will be near a fainter star in Leo, called Denebola. The word “deneb” in star names typically means “tail.” The name Denebola indicates that this star represents the Lion’s Tail.
Our sun travels nearly one degree (two sun-diameters) eastward per day in front of the constellations of the zodiac. The sun passes in front of the constellation Leo each year from around August 10 to September 16, and has its yearly conjunction with the star Regulus on or near August 23.
Visit Heavens-Above to know which constellation of the zodiac presently backdrops the sun.
Bottom line: On the evenings of May 1 and 2, 2020, use the moon to find Regulus, the constellation Leo the Lion’s one and only 1st-magnitude star. By May 3, the moon is closer to Denebola, in the Tail of Leo.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.