The Moon's Great, Straight Wall Gets Solar Spotlight
The Straight Wall, one of the moon’s most spectacular features, is well placed Thursday, April 22, 2010. Full Story.
Credit: Starry Night® Software

On Thursday night, April 22, the sun will rise over the one of the most spectacular topographic features on the moon ? the Straight Wall ? giving skywatchers a good chance to spot the lunar marvel.

The moon is the only astronomical body on which topographical features can be seen in detail with small telescopes or even binoculars. It is fascinating to watch the sunlight playing on these features as the moon rotates.

To locate the Straight Wall (or Rupes Recta, as it?s formally known in Latin) first look for the trio of large craters right in the center of the terminator, the line dividing light and shadow on the moon?s surface: Ptolemaeus, Alphonsus, and Arzachel. Just to the southwest of Arzachel is a large ruined crater, flooded by lava from the Mare Nubium. The Straight Wall is a huge fault crossing this ghost crater. [See the moon's Straight Wall.]

At this time in the lunar month, the Straight Wall, 68 miles (110 km) long, casts a wide shadow. Despite this, it is really not very high, ranging from 800 to 1,000 feet (240?300 meters) in height. Heights of objects close to the terminator are often exaggerated by the glancing rays of the sun.

Although the slope of this fault line looks steep, it is really quite gentle compared to similar fault lines on Earth, only about seven degrees. A cluster of hills at the southern end of the Straight Wall often looks like the handle of a sword, the blade being formed by the Straight Wall itself. Just to the west of the Straight all is the small but deep crater Birt, which is 11 miles (17 km) in diameter and 11,400 feet (3,470 meters) deep.

It will be interesting to look at this area again in a little under two weeks, on the morning of May 6, when the sun is setting on the Straight Wall. The face of the wall, currently in shadow, will then be bathed in the light of the setting sun, a brilliant white line instead of the current black one.

This article was provided to by Starry Night Education, the leader in space science curriculum solutions.