Old Moon near Mercury
Old Moon near Mercury
This Week’s Sky: March 16 to 22

This week’s night skies are busy, with planetary conjunctions, lunar passes, the vernal equinox and evening zodiacal light.

This week’s night skies are busy with planetary conjunctions, lunar passes, the vernal equinox and evening zodiacal light.

Monday, March 16 at 9:34 GMT – Last Quarter Moon

Last Quarter Moon

At its last quarter phase, the Moon rises around midnight and remains visible in the southern sky during morning daylight. At this time, the Moon is illuminated on the eastern side, towards the pre-dawn sun. Last quarter moons are positioned ahead of the Earth in our trip around the Sun. About 3.5 hours later, Earth will occupy that same location in space. After this phase, the waning Moon will traverse the last quarter of its orbit around the Earth, on the way to New Moon.

Wednesday, March 18 pre-dawn – Crescent Moon near Mars and Jupiter

Crescent Moon near Mars and Jupiter

In the southeastern sky before dawn on Wednesday, March 18, the waning Crescent Moon will take up a position less than two finger widths below (or 1.5 degrees to the celestial south of) Mars and Jupiter. All three objects will fit into the field of view of binoculars (red circle) and will make a lovely wide field photograph when composed with nearby Saturn and some interesting foreground terrain. For any of our readers in southern South America, South Georgia, Antarctica and the Kerguelen Islands — from approximately 6:40-7:40 a.m. GMT, you will be able to see the Moon occult Mars.

Thursday, March 19 pre-dawn – Old Moon passes Saturn

Old Moon passes Saturn

Low in the southeastern sky before dawn on Thursday, March 19, the waning crescent Moon will continue its tour of the bright morning planets. After the Moon rises at 5:30 a.m. local time, its very slender crescent will be positioned a palm’s width to the lower left (or six degrees to the celestial southeast of) Saturn. Observers from Europe and Africa to Asia will see the Moon much closer to Saturn. Wherever you view them from, the duo, plus nearby Mars and Jupiter, will make a terrific wide field photograph when composed with some interesting foreground terrain.

Friday, March 20 at 3:50 GMT – Spring Equinox

Spring Equinox

On Friday, March 20 at 3:50 GMT (or 10:50 p.m. EDT on Thursday) the Sun will cross the celestial equator traveling north, marking the vernal equinox in the Northern Hemisphere and the beginning of northern spring.

Friday, March 20 pre-dawn – Mars joins Jupiter

Mars joins Jupiter

The southeastern pre-dawn sky on Friday, March 20 will feature a close conjunction of the planets Mars and Jupiter. The pair will rise at about 4:30 a.m. in your local time zone. From Thursday to Saturday, Mars’ faster orbital motion will bring it within one degree to the south of Jupiter. On Friday morning, the two planets will be separated by only 42 arc-minutes (the Moon’s apparent diameter is 30 arc-minutes). Throughout the encounter, Mars and Jupiter, with its four moons, will appear together in the field of view of a backyard telescope at high magnification (red circle).

Saturday, March 21 before sunrise – Old Moon near Mercury

Old Moon near Mercury

Look very low in the east-southeastern sky before sunrise on Saturday, March 21 to see the delicate crescent of the old Moon sitting a palm’s width to the lower right (or six degrees to the celestial southwest) of Mercury. The optimal viewing time for them will occur between about 6:45 and 7 a.m. local time. If you use binoculars, be sure to put them away before the sun begins to rise.

Tuesday, March 10 to Tuesday, March 24, after evening twilight – Evening Zodiacal light

Evening Zodiacal light

As stated last week, for about an hour after dusk during the two-week period preceding the new moon on March 24, Northern Hemisphere observers can look west-southwest for a broad wedge of faint light rising from the horizon. It will be below Venus and centered on the ecliptic (green line). This is the zodiacal light – reflected sunlight from interplanetary particles of matter concentrated in the plane of the solar system. You will need to observe from a location without light pollution. Don’t confuse the zodiacal light with the brighter Milky Way to the northwest. Observers in the Southern Hemisphere can see the zodiacal light in the eastern pre-dawn sky starting around March 23. 

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.

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