Tuesday, April 20 – First quarter Moon (at 6:59 GMT)
When the moon completes the first quarter of its orbit around Earth at 2:59 a.m. EDT (or 6:59 GMT) on Tuesday, April 20, the relative positions of the Earth, sun, and moon will cause us to see it half-illuminated – on its eastern side. At first quarter, the moon always rises around noon and sets around midnight, so it is also visible in the afternoon daytime sky. The evenings surrounding first quarter are the best for seeing the lunar terrain when it is dramatically lit by low-angled sunlight.
Tuesday, April 20 – Moon passes the Beehive (overnight)
Several days after passing Messier 35, the waxing gibbous Moon will encounter another prominent open star cluster named Messier 44, Praesepe, and the Beehive, in Cancer. In the southwestern sky after dusk on Tuesday, April 20, the Moon will be shining several finger widths to the upper left (or 3.5 degrees to the celestial northeast) of that cluster. To better see the “bees,” hide the bright Moon just beyond the upper edge of your binoculars’ field of view (red circle). Observers in western Africa and Europe, and the United Kingdom will see the Moon while it is somewhat closer to Messier 44.
Thursday, April 22 – Lyrids Meteor Shower peak (pre-dawn)
The annual Lyrids Meteor Shower, derived from particles dropped by Comet C/1861 G1 (Thatcher), runs from April 16 to 30, and is predicted to peak in intensity at approximately 12:00 p.m. UTC on Thursday, April 22. The Lyrids can produce up to 18 meteors per hour at the peak, with occasional fireballs. The most meteors will appear between midnight and dawn on Thursday, with a reasonable number of meteors on the mornings before and after, too. Lyrids meteors will streak away from a point in the sky (the shower’s radiant) near the bright star Vega, which will be high in the eastern sky before dawn. The bright, waxing gibbous moon will reduce the number of Lyrids in 2021 – but it will set just before 4 a.m. local time – providing about an hour of dark sky before dawn.
Thursday, April 22 – Gibbous Moon near stationary Vesta (evening)
On Thursday, April 22, the main belt asteroid designated (4) Vesta will complete a westward retrograde loop that it began in January (red path with labeled dates:time). After briefly pausing its motion through the stars of central Leo, Vesta will resume an eastward trajectory. This week look for magnitude 6.65 Vesta sitting less than a finger’s width below (or 0.5 degrees south-southeast of) the star 51 Leonis. On Thursday night only, the bright, waxing gibbous moon will pass less than a palm’s width below Vesta. (Image: Apr22b-2021 at 9 pm – Gibbous Moon near Stationary Vesta.jpg)
Saturday, April 24 – Mercury moves past Venus (after sunset)
Immediately after sunset on the evenings surrounding Saturday, April 24, look just above the west-northwestern horizon, where speedy Mercury will be climbing past much brighter Venus. On Saturday, Mercury will be positioned a thumb’s width to Venus’ lower right (or 1.25 degrees to the celestial northwest). On Sunday and Monday Mercury will ascend to Venus’ upper right. The best viewing times will be at about 8 p.m. local time. Ensure that the sun has completely disappeared below the horizon before using binoculars (red circle) or telescopes in your search.
Chris Vaughan is a science writer, geophysicist, astronomer, planetary scientist and an “outreach RASCal.” He writes Astronomy Skylights, and you can follow him on Twitter at @astrogeoguy. He can also bring his Digital Starlab portable inflatable planetarium to your school or other daytime or evening event. Contact him through AstroGeo.ca to tour the universe together.