First Quarter Moon
First Quarter Moon
This Week’s Sky: January 26 to February 2

From a waxing crescent Moon near Uranus to the Moon occulting the asteroid Vesta, here are the highlights in This Week’s Sky.

From a waxing crescent Moon near Uranus to the Moon occulting the asteroid Vesta, here are the highlights in This Week’s Sky.

Monday, January 27 early evening – Venus Kisses Neptune

Venus Kisses Neptune

In the western sky after dusk on Monday, January 27, the orbital motion of the very bright planet Venus (red path with dates and times indicated) will take it very close past the distant and far dimmer planet Neptune. Closest approach will occur at 20:00 GMT, when the two planets will be separated by only four arc-minutes! Observers in the Americas will have to wait until full darkness falls a few hours later to see Neptune – by then sitting only 10 arc-minutes to the celestial north of Venus. Throughout the encounter, Venus and Neptune will appear together within the field of view of a backyard telescope (red circle), but Venus will far outshine Neptune’s tiny blue disk. Note that your telescope’s optics will likely flip and/or invert the arrangement shown here. 

Tuesday, January 28 evening – Young Moon near Venus

Young Moon near Venus

In the southwestern sky after sunset on Tuesday, January 28, the young Moon’s slim crescent will be positioned a binoculars’ field width to the upper left (or six degrees to the celestial southeast) of very bright Venus. By the time Venus sets at about 8:45 p.m. local time, the Moon’s eastward orbital motion will have carried it a bit farther from Venus.

Friday, January 31 evening – Moon and Uranus

Moon and Uranus

In the southwestern sky during the evening hours of Friday, January 31, the waxing crescent Moon will be positioned a palm’s width to the lower left (or six degrees to the celestial southwest) of Uranus. While bright moonlight will hamper views of far less bright Uranus, use the Moon to identify Uranus’ location and then look for that dim planet on a night when the Moon is less intrusive.

Saturday, February 1 evening – The Moon Meets Vesta

The Moon meets Vesta

In the southwestern sky on the evening of Saturday, February 1, the orbital motion of the waxing Moon (green line) will carry it toward the main belt asteroid designated (4) Vesta. Binoculars and backyard telescopes will be required to see the magnitude 7.9 asteroid. By the time the Moon sets at about 1:20 a.m. local time, Vesta will be positioned less than two finger widths to the upper right (or two degrees to the celestial east) of the Moon. Hours later, at approximately 8:50 GMT on February 2, observers in southern Asia, eastern Afghanistan, northern Philippines, China, Japan, eastern Russia, Alaska, and western Canada will see the Moon occult Vesta.

Sunday, February 2 at 1:42 GMT – First Quarter Moon

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.

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.