Did you catch the full moon last night with Jupiter as a “punctuation mark” just above it? Over Iowa, the king of planets was almost washed out in the moonlight and hazy sky in the east last night.
Today’s Astronomy Picture of the Day shows the difference between “super” and “micro” full moons. Tonight’s nearly full moon will be slightly larger, but still very much smaller than the “super” of this past May. The moon’s orbit brings it about 2,000 miles closer tonight as compared to the same time last night. That difference will be very hard to detect without a reference point. Interesting to note that the “micro” moon travels more slowly in its orbit than the “super.” Any reference there is washed out by rotation of the Earth and the moon’s apparent movement through the sky. If you watched at different times last night through this morning, you would notice movement of the moon relative to the planet Jupiter.
In a dark sky, background stars will show this, with two observing times separated by a few hours. Winter affords younger children a chance to notice this. Go outside just after sunset and see if the moon is near a particular star or two. Then return just before bedtime and see if the position of our natural satellite has shifted. If the skies are clear the next night, you will see a big jump. But note: observe the moon at exactly the same time.
How much does the moon actually move against the background stars? That’s easy to figure out. 360 degrees make up a circle. The moon orbits the Earth in about a month. Divide and you get about twelve degrees a day. If you extend two fists side by side with straight arms, that’s almost 12 degrees.
If stars are hard to see in your city skies, you can also observe near moonrise or moonset. If, say, the moon is low in the east at 7pm tonight. Mark two fists toward the horizon and under your second hand will be about where the moon will appear at 7pm tomorrow night. Make sense? I hope so. One can also look up at the night slky. If you watch long enough, closely enough, you will see many subtle and beautiful things.