The week of May 16-22 takes us from Day 16 to Day 23. This week we will highlight the moon crater Aristarchus.

moon crater AristarchusAristarchus: [NW/G5; L=47°W] The moon crater Aristarchus is the brightest spot on the Moon. It is so bright that Sir William Herschel2 mistook it for an erupting volcano, and its glow can even be seen coming through on the dark side of the Moon on Saturday & Sunday when it is illuminated only by earthshine. While you’re at it, see if you can spot segments of the Tycho ray system which are also visible under earthshine.


1 Aristarchus of Samos: (310-230 BCE) Greek astronomer who was the first person to teach that the Earth revolved around the Sun and rotated on its axis, hence he is frequently referred to as the “Greek Copernicus.” (Tragically, most of his writings went up in flames when the Great Library at Alexandria was burned.) For his belief that the Sun was at the center of the Solar System, it was suggested by Cleanthes the Stoic that he should be punished for impertinence to the gods. (It took a while, but the idea eventually caught on. Eighteen hundred years later the monk Giordano Bruno was burned at the stake in Rome for making similar suggestions. Bruno’s crimes included a diverse list of other so-called heresies, such as asserting the existence of other inhabited worlds and not believing in the Trinity, the divinity of Christ, or the virgin birth.)

2 18th c. English astronomer who discovered Uranus.


It is highly recommended that you get a copy of Sky and Telescope’s Field Map of the Moon, the very finest Moon map available for use at the telescope. It is available for $10.95 at and on Amazon. All features mentioned in this blog will be keyed to the grid on the Field Map and will look like this: Plato: [NW/D9]

Courtesy of Gray Photography of Corpus Christi, Texas
Lunar photos: NASA / USGS / BMDO / LROC / ASU / DLR / LOLA / Moon Globe. Used by permission

Andrew Planck
Brightest Spot on the Moon: Moon Crater Aristarchus

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