This is Dudley Observatory’s Skywatch Line for Friday, March 20, through Sunday, March 22, written by Sam Salem.
On Friday, Sun rises at 6:58am and sets at 7:08pm, the waning crescent Moon rises at 5:37am and sets at 3:31pm. Look very low in the east-southeastern sky before sunrise on Saturday to see the delicate crescent of the old Moon sitting a palm’s width to the lower right of Mercury.
Friday is officially the first full day of spring. At equinox, the Sun rises virtually due east and sets due west. That means, on the day of an equinox, the setting Sun hits the horizon at its steepest possible angle. At a solstice, the Sun is setting farthest north or farthest south of due west. The farther the Sun sets from due west along the horizon, the shallower the angle of the setting Sun.
Look west-southwest for a broad wedge of faint light rising from the horizon. It will be below Venus and centered on the ecliptic. 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.
On Friday, the southeastern pre-dawn sky will feature a close conjunction of Mars, at magnitude 0.9, and the -2.1 magnitude Jupiter. The pair will rise few minutes after 4am. On Friday morning, the two planets will be separated by only 42 arc-minutes. The Moon’s apparent diameter is 30 arc-minutes. The pair lies roughly 5.5 degrees below Rho1 (ρ1) Sagittarii. 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. Look east of the pair, and you’ll see Saturn, at magnitude 0.7, 7 degrees east of Jupiter.
On Friday, once darkness falls, look for the constellations Aries and dimmer Triangulum lurking some 12 degrees to 16 degrees from brilliant Venus. Above Venus by 13 degrees are the Pleiades. Venus sets few minutes after 11pm.
The constellation Coma Berenices, also known as Berenice’s Hair, is an open star cluster, a loose collection of stars held together by gravity. The Coma star cluster requires a dark sky to be seen. One way to find it is to use constellation Leo the Lion. Leo is relatively easy to see. The front part of the Lion looks like a backwards question mark, and the back part is a little triangle, which includes the star Denebola. The word Deneb in a star name means tail. This star marks the tail of Leo. Use the pointer stars in the Big Dipper to locate Leo. Instead of going northward from the pointer stars to Polaris, the North Star, go southward instead to find the constellation Leo. Imagine that Leo is holding his tail out. In the place where you might see a “puff” at the end of the Lion’s tail, you’ll notice a fuzzy patch, not too far away from Denebola. This is the constellation Coma Berenices, or Berenice’s Hair. The constellation Coma Berenices once was considered part of the constellation Leo. Try binoculars if you can’t spot this group of stars with the unaided eye.