Theon Junior is a
lunar
Lunar most commonly means "of or relating to the Moon".
Lunar may also refer to:
Arts and entertainment
* ''Lunar'' (series), a series of video games
* "Lunar" (song), by David Guetta
* "Lunar", a song by Priestess from the 2009 album ''Prior t ...
impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...
that is located just to the west-southwest of the crater
Delambre
Jean Baptiste Joseph, chevalier Delambre (19 September 1749 – 19 August 1822) was a French mathematician, astronomer, historian of astronomy, and geodesist. He was also director of the Paris Observatory, and author of well-known books on th ...
. It forms a matching pair with
Theon Senior, only a couple of crater diameters to the north-northwest. The crater is circular and bowl-shaped, with a small floor at the bottom of the high, sloping interior walls. It is named for
Theon of Alexandria
Theon of Alexandria (; grc, Θέων ὁ Ἀλεξανδρεύς; 335 – c. 405) was a Greek scholar and mathematician who lived in Alexandria, Egypt. He edited and arranged Euclid's '' Elements'' and wrote commentaries on works ...
, a 4th-century Greek astronomer and mathematician. The crater is from the
Eratosthenian
The Eratosthenian period in the lunar geologic timescale runs from 3,200 million years ago to 1,100 million years ago. It is named after the crater Eratosthenes, which displays characteristics typical of craters of this age, including a surface ...
period, which lasted from 3.2 to 1.1
billion
Billion is a word for a large number, and it has two distinct definitions:
*1,000,000,000, i.e. one thousand million, or (ten to the ninth power), as defined on the short scale. This is its only current meaning in English.
* 1,000,000,000,000, i.e ...
years ago. It is 17 kilometers in diameter and the difference in height at its rim and its deepest part is 3,580 meters.
Satellite craters
By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Theon Junior.
References
External links
Theon Junior at The Moon Wiki* {{cite web, last = Wood , first = Chuck , date = December 12, 2006 , url = http://www.lpod.org/?m=20061211 , title = How Deep is That Hole , publisher = Lunar Photo of the Day, url-status=dead, archive-url=https://web.archive.org/web/20110614233616/http://www.lpod.org/?m=20061211, archive-date=June 14, 2011 - includes a couple of craters such as Theon Junior
Impact craters on the Moon
Eratosthenian