What's Up...Astronomical slowdown
By Vernon Whetstone
Just as we all have busy days and slow days, this is a slow time astronomically speaking.
The only bright objects in the evening sky this week are the planet Jupiter and a just-passed first-quarter moon, both of which can be seen about an hour after sunset.
The moon will be almost due south and Jupiter will be just above the eastern horizon.
Jupiter was at opposition (opposite the Sun in the sky) last month but still rises close to sunset and sets close to sunrise and can be seen all night long.
Both, however, can be interesting objects through either binoculars or a telescope.
Even at low power magnification Jupiter presents a nice sight of the four Galilean moons and the prospect of the two dark bands of the equatorial cloud belts.
The moon, however, presents even more interesting viewing prospects. Since it is now just past first quarter, the terminator (the dark shadow line dividing the light half and the dark half) makes a nice guide for three lunar craters.
The three can be seen using just binoculars, but a better view can be obtained using a telescope.
The largest one on top is Ptolemaeus. It is about 95 miles in diameter. If using a telescope look for a smaller crater in the floor of the larger crater.
Next, a smaller crater just below Ptolemaeus is Alphonsus. In a telescope the floor of this crater is not smooth. There is a raised ridge running from top to bottom.
It was here in Alphonsus that the lunar exploring spacecraft, Ranger 9, crashed (an early version of NASA’s landing techniques) in 1965 after photographing the moon’s surface.
The smallest, and lowest, of the three is Arzachel. It is also the youngest with a noticeably more rugged rim and floor. There is a large peak in the center of the crater that will pick up sunlight before it brightens the crater floor.
One more smaller crater is lined up with the three biggest ones. Tucked in below and left of the center crater is Alpetragius. At first quarter the floor of this crater cannot be seen as it is still in the shadow of the crater rim.
As the days pass and the Sun gets higher it will illuminate more of the interior eventually showing a rounded dome in the center instead of the usual central peak.
Lunar craters are normally named after famous astronomers. If you want some fun, and more history, Google each of the names.
SKY WATCH: Moon at first quarter yesterday. Saturn returns to visibility as a morning object. Look about a half-hour before sunrise in the east. The planet will be above and left of Spica, the brightest star in Virgo, the Maiden. As the month passes Venus will rise higher into the sky for easier viewing. In the west about 45 minutes after sunset look for bright Venus and dim Mercury. The pair will travel together for the next two weeks before Venus rises higher and Mercury starts to sink back toward the horizon. Binoculars will be needed to pull the pair out of the “soup” at the horizon.