The 13 Greatest Astronomers in History And Their Achievements

Here are 13 of the greatest astronomers in history who have shaped our understanding of the known universe and created science of astronomy.

Hipparchus was a Greek mathematician and astronomer. None of his works has survived, however, we know of them via Ptolemy, the last of the traditional Greek astronomers, who made a star catalogue in 140 AD. After seeing a Nova in 134 BC, Hipparchus catalogued the positions of 850 stars in case another popped into view. By comparing his values with some made 150 years previous, he came upon the precession of the equinoxes. He also founded the magnitude system we use today.

Ptolemy, as he's always referred to, lived and worked in Alexandria, however, he was Greek. His original works have been lost, however, his main book has come down to us by way of its translation. He drew up a star catalogue which remained the standard for hundreds of years. It was based on that of Hipparchus, however, Ptolemy extended and advanced it. He introduced the Earth-centered system of the Universe to its highest degree of perfection and, although it was wrong, it fitted the facts as he knew them. Ptolemy additionally compiled the first map of the civilised world primarily based on astronomical observations. Without his work we would know much less about ancient science than we do, he well deserves to be remembered as the "Prince of Astronomers".

Born in Pisa, Italy, and referred to as the daddy of modern astronomy, Galileo is among the greatest astronomers and figures in the history of science. His actions extended into many fields, including philosophy, mathematics and physics. Galileo is without a doubt best remembered as the first real telescopic astronomer. The first telescopes of which we have definite knowledge were made in Holland in 1608. Galileo was then at Pisa, but when he heard about the Dutch discovery he made a telescope for himself, sparing neither trouble nor expense. Galileo used the telescope to make a sequence of impressive discoveries: he noticed the craters of the Moon, the phases of Venus, the four main satellites of Jupiter and the myriad stars of the Milky Way.

Kepler broke free of the classical tradition in astronomy, preferring the methods of science to the ideas of the ancient sages. In 1600, Tycho Brahe who had compiled exact observations of Mars asked Kepler to examine its orbit. Eight years later, he discovered not only that it was elliptical, but that all the other planets have elliptical orbits too. Kepler additionally observed a star in 1604 that suddenly brightened. Now referred to as Kepler's Star, it was the last supernova observed in the Milky Way.

Hevelius was a rich brewer and councillor who made many observations in his spare time. He built a big rooftop observatory that employed a huge telescope of 130ft (40m) focal length to look at the Moon, from which he drew beautiful maps. His work in positional astronomy resulted in a star catalogue of 1,564 stars being published - probably the most complete of its day. Hevelius used a quadrant for this and was the last astronomer to do major observational work without assistance from a telescope.

Edmond Halley made monumental contributions to just about every branch of physics and astronomy. Using his knowledge of geometry and historic astronomy, Halley connected the comet sightings of 1456, 1531, 1607 and 1682 to the same object which he accurately predicted would return in 1758. Halley would be long dead by then, which is why not everybody took his prediction seriously, however, the comet was named after him nonetheless. He died in 1742 but the comet is his lasting legacy.

William Herschel, the discoverer of Uranus, was a famed observational astronomer of the 18th century. King George III, who was a powerful supporter of scientific enquiry, hired him on a wage of £200 a year and financed the development of several large telescopes. Herschel discovered Uranus in 1781, which introduced him to worldwide fame, followed by two of its moons in 1787. He additionally made about 400 telescopes, culminating in the giant 40ft (12m) reflector.

John was the son of William Herschel. He studied mathematics at Cambridge and started to help his father in 1816. In 1834 he went to the observatory on the Cape of Good Hope to survey the southern skies and, whilst there, discovered no fewer than 2,000 nebulae and 2,000 double stars. John found himself amid controversy in 1835 when the New York Sun newspaper spun a hoax to boost its sales claiming that he had discovered animals dwelling on the Moon.

Huggins founded astronomical spectroscopy, being the first to make extensive investigations of stellar spectra, and was the discipline's pioneer. In 1863 he was the first to show that stars are composed of chemical elements that occur in the solar spectrum. That same year he scored another first by measuring the redshift of Sirius, following which he measured the velocities of many stars. Huggins's spectroscope additionally proved that emission nebulae are glowing clouds of gas.

Hertzsprung discovered the two main groupings of stars - the luminous giants and supergiants, and the dwarfs now referred to as main-sequence stars. Henry Norris Russell made the same discovery independently. Both created diagrams to show the grouping of those stars, which are these days referred to as Hertzsprung-Russell diagrams. Hertzsprung additionally measured the distances to several variable stars, which he then used as a measuring stick to find the distance of the Small Magellanic Cloud.

Hubble, who trained as a legal professional, was the American observational astronomer who discovered the expansion of the Universe. In 1923-24 he used the Mount Wilson 100-inch telescope to measure the distance to 18 galaxies - an enormous success. When he compared those distances to redshift measured by others, he discovered that a galaxy's distance is proportional to its velocity. He thus showed the theory of an expanding Universe, which is key to cosmology.

Kuiper, probably the most prominent planetary scientist of his time, discovered Uranus's moon Miranda in 1948 and Neptune's Nereid in 1949. A pioneer in planetary atmospheric research, he discovered the existence of a methane-laced atmosphere above Saturn's moon Titan and carbon dioxide in the atmosphere of Mars in 1944. Kuiper is generally best remembered for his prediction of enormous swarms of comet cores and small icy bodies beyond Neptune: the Kuiper Belt.

Sir Bernard Lovell started his scientific career in cosmic ray research at Manchester University; throughout the war, he was a radar pioneer. Subsequently, he became interested in the brand new science of radio astronomy and put forward the theory of building a completely steerable radio telescope with a dish 250ft (76m) in diameter, to be set up at Jodrell Bank in Cheshire, which was at the time the only telescope capable of tracking the first Russian satellite Sputnik 1. The telescope has since pioneered research into quasars and pulsars, radio galaxies, starburst regions and active galactic nuclei. The telescope has never been idle!