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Agrippa (astronomer)
Encyclopedia
Agrippa was a Greek astronomer
. The only thing that is known about him regards an astronomical observation that he made in 92 AD, which is cited by Ptolemy
(Almagest
, VII, 3). Ptolemy writes that in the twelfth year of the reign of Domitian
, on the seventh day of the Bithynia
n month Metrous, Agrippa observed the occultation of a part of the Pleiades
by the southernmost part of the Moon
.
The purpose of Agrippa's observation was probably to check the precession
of the equinox
es, which was discovered by Hipparchus
.
The lunar crater Agrippa
is named after him.
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
. The only thing that is known about him regards an astronomical observation that he made in 92 AD, which is cited by Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
(Almagest
Almagest
The Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt,...
, VII, 3). Ptolemy writes that in the twelfth year of the reign of Domitian
Domitian
Domitian was Roman Emperor from 81 to 96. Domitian was the third and last emperor of the Flavian dynasty.Domitian's youth and early career were largely spent in the shadow of his brother Titus, who gained military renown during the First Jewish-Roman War...
, on the seventh day of the Bithynia
Bithynia
Bithynia was an ancient region, kingdom and Roman province in the northwest of Asia Minor, adjoining the Propontis, the Thracian Bosporus and the Euxine .-Description:...
n month Metrous, Agrippa observed the occultation of a part of the Pleiades
Pleiades (star cluster)
In astronomy, the Pleiades, or Seven Sisters , is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky...
by the southernmost part of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
.
The purpose of Agrippa's observation was probably to check the precession
Precession
Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...
of the equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...
es, which was discovered by Hipparchus
Hipparchus
Hipparchus, the common Latinization of the Greek Hipparkhos, can mean:* Hipparchus, the ancient Greek astronomer** Hipparchic cycle, an astronomical cycle he created** Hipparchus , a lunar crater named in his honour...
.
The lunar crater Agrippa
Agrippa (crater)
Agrippa is a lunar impact crater that is located at the southeast edge of the Mare Vaporum. It is located to the north of the crater Godin, and the irregular Tempel lies just to the east. To the north and northeast, the rille designated Rima Ariadaeus follows a course to the east-southeast,...
is named after him.