This morning the last quarter moon peered down over my house from high up in the southwestern sky. It was very plain to see. Have you noticed the moon lately in the daytime? For northern hemisphere observers, it’s out nearly all morning long if your sky is clean and blue.
There are two reasons for the moon’s easy visibility. The first has to do with phase. At full phase, it’s exactly opposite the sun – as far as it can get. When the sun sets, the moon rises, and when the moon sets the next morning, the sun rises. Each day after full moon, the moon moves about one outstretched fist eastward (left) in the direction of the sun as it orbits the Earth. 7 days after full – last quarter phase – it rises around midnight and set around noon the following day. That means it’s still up in the west well after sunrise.
The second reason for the moon’s easy visibility has to do with the direction of its path after full phase. Earlier this month, you might recall how low the full moon was in the southern sky. From my home it skirted the tree tops. That’s because it reached the lowest point in its path around the sky. The sun occupies the same spot in late December at the start of winter. Recall that both it and the moon follow the same path in the sky called the ecliptic.
Having hit its lowest point, the moon had nowhere to go but up. Now at last quarter phase, it’s positioned in Aries, halfway to the summer solstice point. Not only is the moon at a higher altitude, but like the spring sun vs. the winter sun, it hangs around longer in the sky. Over the coming mornings, the moon will wane to a crescent, get closer to the sun and also higher up in the sky. Watch for it.
If you prefer your moon observing in a dark sky, it will be passing the planet Jupiter this weekend. Watch for a nice pairing of the two tomorrow (Saturday) and Sunday mornings. You can either go out around 1:30-2 a.m. when they first come up in the east or wait until dawn to see them nicely placed in the southeastern sky.
In case you didn’t see this cool photo of Atlantis, here it is. Be sure to click the image to see the BIG version. It shows the shuttle’s glowing plasma trail from superheated air as it re-entered the Earth’s atmosphere traveling at thousands of miles per hour. Look carefully to follow the trail all the way down to the cloud tops. Stars show in the picture, because it was taken in twilight before sunrise.