Alpetragius (crater)

Alpetragius is a prominent lunar impact crater located on the eastern edge of Mare Nubium. It is named after the Arab astronomer Al-Bitruji (Latinized as Alpetragius).

Description:

The crater is distinguished by its unusually high central peak, which rises to a height of approximately 2,000 meters (6,600 feet) above the crater floor. This peak is thought to be formed from material forced upwards during the impact event. Alpetragius has a relatively small diameter of about 40 kilometers (25 miles). Its walls are heavily eroded, with several breaches and landslide features visible. The crater floor is relatively smooth and dark, likely due to subsequent lava flows.

Location and Relationships:

Alpetragius lies southeast of the larger crater Alphonsus, and northeast of Arzachel. The prominent rille system known as the Rimae Arzachel passes near the southern rim of Alpetragius. The crater's location within Mare Nubium contributes to its dark appearance, contrasting with the brighter highlands surrounding the mare.

Formation:

Like most lunar craters, Alpetragius is believed to have been formed by the impact of a meteoroid or asteroid onto the lunar surface. The high central peak suggests a powerful impact event. The eroded state of the crater walls indicates that it is a relatively old feature.

Observation:

Alpetragius is a popular target for amateur astronomers due to its distinctive central peak. It is best observed during periods of low sun angle, such as during the first or last quarter of the lunar cycle, when the shadows cast by the peak and crater walls are most prominent.