This week, the Moon waxes as it passes the Messier 35 and Messier 44, while Comet PanSTARRS passes the Heart Nebula and Venus passes Uranus.
Monday, March 2 at 19:57 GMT — First quarter Moon
When the Moon reaches its first quarter phase, the relative positions of the Earth, Sun, and Moon cause us to see the Moon half illuminated — on the western (right-hand) side. Sunlight striking the Moon at a shallow angle produces spectacularly illuminated landscapes along the pole-to-pole terminator that separates the lit and dark hemispheres. First quarter moons rise at noon and set at midnight, so they are visible starting in the afternoon hours. The term first quarter refers not to the Moon’s appearance, but the fact that our natural satellite has now completed the first quarter of its orbit around Earth, counting from the last new Moon.
Tuesday, March 3 overnight — Waxing Moon passes Messier 35
In the western sky on the night of Tuesday, March 3, the waxing gibbous Moon’s orbital motion (green line) will carry it through the toes of Gemini, and past the prominent open star cluster Messier 35. At closest approach before dawn on Wednesday morning, the Moon will be positioned less than two finger widths below (or 1.75 degrees to the celestial south of) the cluster. By that time, the moon will have set for everyone except observers on the west coast and the Pacific Ocean region.
Friday, March 6 evening – Moon near the Beehive Cluster
In the southeastern sky after dusk on the evening of Friday, March 6, the bright Moon will be positioned less than two finger widths to the lower left (or 1.75 degrees to the celestial east) of the large open star cluster known as the Beehive or Messier 44 in the constellation of Cancer, the Crab. The Moon passes close to, or through, this cluster frequently because the Beehive is located only a finger’s width north of the ecliptic (green line). To see the cluster’s stars, try placing the bright Moon just outside the field of view of your binoculars (red circle). As the night wears on, the moon will move farther away from the cluster, and the rotation of the sky will raise the Moon to the cluster’s upper left.
Saturday, March 7 all night – Comet PanSTARRS passes the Heart Nebula
On the nights surrounding March 7, the orbital motion (labelled red path) of comet C/2017 T2 (PanSTARRS) will take it past the Heart Nebula (or IC 1805) – setting the stage for a lovely astro-image. On those dates, the comet will be the easier of the two objects to observe in backyard telescopes. Find it a few finger widths above the sideways, W-shaped constellation of Cassiopeia in the northwestern evening sky – approximately 2.5 degrees east of Cassiopeia’s topmost star, medium-bright Segin, also known as Epsilon Cass. This comet is predicted to brighten by May. For now, it will appear as a small, greenish, fuzzy patch.
Sunday, March 8 evening – Venus passes Uranus
On the evenings surrounding Sunday, March 8, the faster orbital motion of the very bright planet Venus (red line) will carry it past relatively dim, blue-green Uranus in the western evening sky. At closest approach on Sunday, Uranus will be positioned just two finger widths to the lower left (or 2 degrees to the celestial south) of Venus. For several nights, both planets will appear together in the field of view of binoculars (red circle) – although Uranus will about a thousand times fainter than Venus!
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.