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Eugenios
Antoniadi (1870-1944) was a Frenchman best known for his
planetary observations of the planets Mercury and Mars. Using an
83 cm refracting telescope, he produced a detailed map of the surface
of Mars. So accurate was this map that most of the features on it
have been confirmed by recent spacecraft missions. In 1933, he became
the first to produce a detailed map of the surface of Mercury, naming
some of the surface features known today. Mercury's 450 km long
Antoniadi ridge is named in his honor. |
Aristarchus
of Samos (310-230 BC) was a Greek mathematician and astronomer
who was an advocate of the heliocentric
model, in which all the planets orbit around the Sun. This argument
was fully accepted seventeen centuries later. Aristarchus' only
surviving text is his Treatise on the Sizes and Distances
of the Sun and Moon.
Rolf
Dyce, together with Gordon Pettengill, measured
the spin rate of Mercury using radar pulses reflected from
the planet's surface. The two researchers concluded that
Mercury requires only about 59 days (two-thirds of a orbital
period) to rotate once about its axis, rather than the 88
days that had been claimed by earlier observers. He is Professor
Emeritus at Cornell University.
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Johann Franz Encke (1791-1865)
is known for determining the orbit of a comet
that was later named for him. Using this information, he
determined quite accurately the mass of the Mercury. He
also studied the rings of Saturn.
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Eudoxus of
Cnidus (408-355 BC) was a Greek astronomer, mathematician
and philosopher, one of the most renowned of his day. He devised
a planetary system based on spheres. Eudoxus also excelled as
a mathematician; his Theory of Proportions formed the
basis for Book V of Euclid's Elements.
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Galileo
(1564-1642) was an Italian who in 1609 invented
a telescope that could magnify an object by twenty times.
He turned this telescope on the planets, discovering four
moons of Jupiter and the phases of Venus. He was also the
first to use a telescope to view the planet Mercury. With
these and other observations he helped establish Copernicus'
heliocentric
model.
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Gordon
Pettengill, working in 1965 with colleague Rolf Dyce
at the Arecibo radio telescope, measured the spin rate of
Mercury by reflecting radar pulses from the planet's surface
and studying the pattern of Doppler shifts of the returning
signals. He also developed two-dimensional radar mappings
of the Moon that aided the Apollo missions. For his research
achievements in the field of planetology he was awarded the
1997 Whitten Medal of the American Geophysical Union. He is
presently Professor Emeritus at Massachusetts Institute of
Technology. |
| Ptolemy
(87-150 AD), a Greek mathematician, astronomer, and
geographer, codified the Greek geocentric model of the universe.
In this view, the Sun and other planets were believed to orbit
Earth, in the order Mercury, Venus, Sun, Mars, Jupiter, and
Saturn. The Ptolemaic system predicts the positions of the
planets accurately enough for naked-eye observations, and
is described in his Mathematical Syntaxis (widely
called the Almagest),
a thirteen-book mathematical treatment of of astronomy. |
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Giovanni
Schiaparelli (1835-1910) is recognized for his observations
of the planet Mars, double stars, and comets. He noted straight
lines on the surface of Mars which he call “canali”
- Italian for channels, and a term often mistranslated as
canals. He also concluded that Venus and Mercury rotate on
their axes, and that these rotations are at very slow rates.
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Hieronymus Schroeter (1745-1816) was a lawyer by
trade, and did not turned his attention to astronomy until
1779. He is best known for his observations of the Moon, Sun
and the planets Mercury, Venus, and Mars. His two volumes
on the detailed landscape of the Moon were used for many years.
Unfortunately, his maps of the Mercurian topography were not
as accurate. |
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Timocharis
(ca 200 B.C.), a Greek philosopher, prepared the first
star catalog in the third century B.C. He was the earliest observer
of Mercury whom we know of by name. It is possible, however, that
that he mistook its morning and evening appearances for two planets.
Giovanni Zupus
(1590-1650), was the first to discover that the planet
Mercury has phases like the Moon and Venus.
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