April 17, 2017
Posted by: Scott Greene
With little light pollution on Little St. Simons Island, it is a great place to explore the night sky. Although it travels through several phases each month, Earth’s moon is usually the most conspicuous sight in the night sky. The moon’s illumination is the result of the sun’s light reflecting off the moon’s surface, and as the moon rotates around the Earth, we are able to see differing proportions of the moon.
The moon is estimated to be about 4.5 billion years old, about the same age as the earth. The most accepted theory for the formation of the moon, is that while the earth was still very young, a rock comparable to the size of Mars collided with Earth. The impact of this collision sent large pieces of rock into Earth’s orbit, which aggregated into one body to form our moon.
Image Credit: GSFC / Arizona State Univ. / Lunar Reconnaissance Orbiter NASA
It takes the moon about one month (28 days) to orbit the earth, and it takes about the same amount of time (27.53 days) for the moon to complete a rotation around its own axis. Consequently, the same side of the moon is always facing Earth. Depending on the phase of the moon, we can see a certain portion of that side each night. At its fullest, we can see a little more than half of the moon (59%). The other 41% is the side that never faces Earth, also known as “the far side.”
The moon’s surface exhibits an interesting array of geographical features. The large dark areas are called seas or maria, and were once huge lava plains. Craters appear much lighter than the maria, and appear like starbursts with lines radiating out from the center. All the craters were formed by meteor collisions. The moon also has mountain ranges, valleys, cliffs, and other changes in topography. The best time to observe these features through binoculars or a scope, is several days before and after the full moon when the angle of the sunlight gives the most definition to its features.