Great astronomers
Hipparchus
Hipparchus of Nicaea was a Greek astronomer who lived in the 2nd century BC, dying in 127BC. The foundations of astronomy were laid down by Hipparchus and survived 1500 years, until they were overthrown by the ideas of Copernicus.Ancient Babylonian records brought back by Alexander the Great from his conquests helped Hipparchus to make his observations of the stars. A Some of Hipparchus’ astronomical knowledge came from the Sumerians, who wrote many of their findings on clay tablets.
Hipparchus was the first astronomer to try to work out how far away the Sun is. The first star catalogue, listing 850 stars, was put together by Hipparchus. Hipparchus was also the first to identify the constellations systematically and to assess stars in terms of magnitude
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Hipparchus carried out his observations at Rhodes. He was the first to pinpoint the geographical position of places by latitude and longitude.
Copernicus
Until the 16th century most people thought the Earth was the centre of the Universe and that everything - the Moon, Sun, planets and stars - revolved around it.Nicolaus Copernicus was the astronomer who first suggested that the Sun was the centre, and that the Earth went round the Sun.This is called the heliocentric view.A In 1543 Nicolaus Copernicus proposed a revolutionary theory - that Earth and other planets move around the Sun. Before this people had believed that the Sun and planets moved around the stationary Earth.
‘The Earth,wrote Copernicus, ‘carrying the Moon’s path, passes in a great orbit among the other planets in an annual revolution around the Sun.’ Copernicus was born on 19 February 1473 at Torun in Poland, and died on 24 May 1543. Copernicus was the nephew of a prince bishop who spent most of his life as a canon at Frauenberg Cathedral in East Prussia . Copernicus described his ideas in a book called De revolutionibus orbium coelestium .The Roman Catholic Church banned Copernicus’s book for almost 300 years.Copernicus’s ideas came not from looking at the night sky but from studying ancient astronomy. Copernicus’s main clue came from the way the planets, every now and then, seem to perform a backward loop through the sky.
The first proof of Copernicus’s theory came in 1609, when Galileo saw (through a telescope) moons revolving around Jupiter.The change in ideas that was brought about by Copernicus is known as the Copernican Revolution. Herschel William Herschel (1738-1822) was an amateur astronomer who built his own, very powerful telescope in his home in Bath, England.
Until Herschel’s time, astronomers assumed there were just seven independent objects in the sky - the Moon, the Sun, and five planets. The five known planets were Mercury, Venus, Mars, Jupiter and Saturn.Uranus, the sixth planet, was discovered by William Herschel in 1781.
William Herschel was one of the greatest astronomers. With the help of his sister Caroline, he discovered Uranus in 1781. He later identified two of the moons of Uranus and Saturn. clip_image002[4] At first, Herschel had thought that the dot of light he could see through his telescope was a star.
But when he looked more closely, he saw a tiny disc instead of a point of light.When he looked the next night, the ‘star’ had moved - this meant that it had to be a planet. Herschel wanted to name the planet George, after King George III, but Uranus was eventually chosen.
Herschel’s partner in his discoveries was his sister Caroline (1750-1848), another great astronomer, who catalogued (listed) all the stars of the northern hemisphere.Herschel’s son John catalogued the stars of the southern hemisphere.Herschel himself added to the catalogue of nebulae. Herschel was also the first to explain that the Milky Way is our view of a galaxy shaped ‘like a grindstone.
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