In what years were each of the planets discovered?

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In what years were each of the planets discovered?

Question #87120. Asked by apathy100.
Last updated Aug 31 2021.

McGruff

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McGruff

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Answer has 8 votes.

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Only 3 of the 9 planets in our solar system have official "discoverers" and "times of discovery". The reason is simple - all of the other planets are easily seen by the unaided human eye. This means that humankind has been looking at these objects (whether they understood what they were or not) since first gazing at the night sky! Three planets required good telescopes for their discovery:

o Uranus was discovered by Sir William Herschel in 1781.
o Neptune was discovered by John Couch Adams in 1846.
o Pluto was discovered by astronomer Clyde Tombaugh in 1930.

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question16.html

One can argue whether or not Pluto is a planet. I included it here for the date reference.

Response last updated by gtho4 on Jan 03 2017.
Oct 25 2007, 9:46 AM

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Answer 1

Mercury	"The earliest mentions of Mercury come from the 3rd millennium BC, when it was known to the Sumerians of Mesopotamia. Mercury's orbit is so close to the Sun that it is difficult to see. This explains why some early astronomers didn’t see it. Viewed from Earth, Mercury is never far from the Sun in the sky. Because the Sun is so bright, Mercury can only be seen in twilight. Timocharis made the first recorded observation of Mercury in 265 BC. https://en.wikipedia.org/wiki/Mercury_%28planet%29
Venus	Venus can be seen with the naked eye so no one really disocovered it and it was known to most or all the ancient civilizations. Also, "One of the oldest surviving astronomical documents, from the Babylonian library of Ashurbanipal around 1600 BC, is a 21-year record of the appearances of Venus" http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/961205a.html https://en.wikipedia.org/wiki/Observations_and_explorations_of_Venus
Earth	:)
Mars	"Mars is much like Venus-- it's very bright and therefore easily spotted in the night sky. Because of this, we don't know who exactly discovered Mars." https://www.windows2universe.org/mars/discovery.html
Jupiter	"Jupiter is the largest planet in our solar system. It is also one of the brighter objects in the night sky. No one knows for sure who discovered Jupiter, but we know the ancient Greeks named him after the god, Zeus." https://www.windows2universe.org/jupiter/jupiter.html
Saturn	"Saturn has been known since prehistoric times. In ancient times, it was the most distant of the five known planets in the solar system (excluding Earth) and thus a major character in various mythologies. Saturn's rings require at least a 75 mm diameter telescope to resolve and thus were not known to exist until Galileo first saw them in 1610." https://en.wikipedia.org/wiki/Saturn#History_and_exploration
Uranus	"Sir William Herschel observed the planet on 13 March 1781 while in the garden of his house at 19 New King Street in the town of Bath, Somerset (now the Herschel Museum of Astronomy), but initially reported it (on 26 April 1781) as a "comet". Uranus had been observed on many occasions prior to its discovery as a planet, but it was generally mistaken for a star. The earliest recorded sighting was in 1690 when John Flamsteed catalogued Uranus as 34 Tauri and observed it at least six times. The French astronomer, Pierre Lemonnier, observed Uranus at least twelve times between 1750 and 1769,[17] including on four consecutive nights." https://en.wikipedia.org/wiki/Uranus#Discovery
Neptune	"Discovered on September 23, 1846 Neptune was the first planet discovered by mathematical prediction rather than regular observation." "It was irregularities in the orbit of Uranus that led John Couch Adams in England and Urbain Le Verrier in France to predict an eighth planet and to embark on an international race for discovery. Galileo's drawings show that he first observed Neptune on December 28, 1612, and again on January 27, 1613; on both occasions, Galileo mistook Neptune for a fixed star when it appeared very close (in conjunction) to Jupiter in the night sky." https://en.wikipedia.org/wiki/Discovery_of_Neptune

Answer 2

Pluto (dwarf planet) - "In 1930, Clyde Tombaugh was searching for a ninth planet as part of a project at Lowell Observatory."
"On February 18, 1930, Tombaugh discovered a possible moving object on photographic plates taken on January 23 and January 29 of that year. A lesser-quality photograph taken on January 20 helped confirm the movement. After the observatory obtained further confirmatory photographs, news of the discovery was telegraphed to the Harvard College Observatory on March 13, 1930. Pluto would later be found on photographs dating back to March 19, 1915."

https://en.wikipedia.org/wiki/Pluto#Discovery

Ceres (dwarf planet) - "It was discovered on January 1, 1801, by Giuseppe Piazzi, and is named after the Roman goddess Ceres—the goddess of growing plants, the harvest, and of motherly love."

https://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29#Discovery

Eris (dwarf planet) - "Eris was discovered by the team of Mike Brown, Chad Trujillo, and David Rabinowitz on January 5, 2005, from images taken on October 21, 2003. The discovery was announced on July 29, 2005"

https://en.wikipedia.org/wiki/Eris_%28dwarf_planet%29#Discovery

Answer 3

star_gazer

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star_gazer

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Answer has 4 votes.

Although visable by the naked eye, Saturn was "discovered" by star gazers in prehistoric times.

https://en.wikipedia.org/wiki/Saturn#Ancient_times_and_observation

Oct 25 2007, 4:55 AM

Answer 4

Mars has been known since prehistoric times. Of course, it has been extensively studied with ground-based observatories. But even very large telescopes find Mars a difficult target, it's just too small.

Venus has been known since prehistoric times. It is the brightest object in the sky except for the Sun and the Moon. Like Mercury, it was popularly thought to be two separate bodies: Eosphorus as the morning star and Hesperus as the evening star, but the Greek astronomers knew better.

Mercury has been known since at least the time of the Sumerians (3rd millennium BC). It was sometimes given separate names for its apparitions as a morning star and as an evening star. Greek astronomers knew, however, that the two names referred to the same body. Heraclitus even believed that Mercury and Venus orbit the Sun, not the Earth.

Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus). It has been known since prehistoric times as a bright "wandering star". But in 1610 when Galileo first pointed a telescope at the sky he discovered Jupiter's four large moons Io, Europa, Ganymede and Callisto (now known as the Galilean moons) and recorded their motions back and forth around Jupiter.

Saturn has been known since prehistoric times. Galileo was the first to observe it with a telescope in 1610; he noted its odd appearance but was confused by it. Early observations of Saturn were complicated by the fact that the Earth passes through the plane of Saturn's rings every few years as Saturn moves in its orbit. A low resolution image of Saturn therefore changes drastically. It was not until 1659 that Christiaan Huygens correctly inferred the geometry of the rings.

Nice site:

http://www.nineplanets.org/history.html

Answer 5

Uranus. It was discovered by William Herschel while systematically searching the sky with his telescope on March 13, 1781.

https://www.sciencemuseum.org.uk/objects-and-stories/uranus-first-planet-discovered-telescope

Mercury, Venus, Mars, Jupiter and Saturn can be seen without a telescope and thus were 'discovered' thousands of years ago. Uranus was the first planet to be sighted by a telescope in 1781. Neptune was sighted in 1848.

https://en.wikipedia.org/wiki/Planets