The Greatest Astronomers
Ever since the dawn of humankind, we have looked out upon the cosmos in awe of the glory of the heavens above. Here we list some of the greatest astronomers who have shaped our understanding of the known universe.
While the spectacular views offered by our night sky haven't changed a great deal over the aeons, our understanding of them has. Knowledge of our universe has gradually expanded over the last few thousand years thanks to the efforts of the greatest astronomers through the ages.
Hipparchus (c190 - 120BC)
Hipparchus was a Greek mathematician and astronomer. None of his works has survived, but we know of them through Ptolemy, last of the ancient 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 earlier, he discovered the precession of the equinoxes. He also founded the magnitude system we use today.
Claudius Ptolemaeus (AD120 - 180)
Ptolemy, as he is always known as, lived and worked in Alexandria, but he was Greek. His original works have been lost, but his main book has come down to us by way of its translation. He drew up a star catalogue which remained the standard for centuries. It was based on that of Hipparchus, but Ptolemy extended and improved it. He brought the Earth-centered system of the Universe to its highest degree of perfection and, though it was wrong, it fitted the facts as he knew them. Ptolemy also compiled the first map of the civilised world based upon 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".
Galileo Galilei (1564 - 1642)
Born in Pisa, Italy, and known as the father of modern astronomy, Galileo is one of the greatest astronomers and figures in the history of science. His activities extended into many fields, including philosophy, mathematics and physics. Galileo is certainly 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 or expense. Galileo used the telescope to make a series of spectacular discoveries: he saw the craters of the Moon, the phases Venus, the four main satellites of Jupiter and the myriad stars of the Milky Way.
Johannes Kepler (1571 - 1630)
Kepler broke free of the classical tradition in astronomy, preferring the methods of science to the thoughts of the ancient sages. In 1600, Tycho Brahe who had compiled precise observations of Mars asked Kepler to examine its orbit. Eight years later, he found not only that it was elliptical, but that all the other planets have elliptical orbits too. Kepler also observed a star in 1604 that suddenly brightened. Now called Kepler's Star, it was the last supernova seen in the Milky Way.
Johannes Hevelius (1611 - 1687)
Hevelius was a wealthy brewer and councillor who made many observations in his spare time. He constructed a large rooftop observatory that employed an enormous telescope of 130ft (40m) focal length to observe the Moon, from which he drew exquisite maps. His work in positional astronomy led to a star catalogue of 1,564 stars be published - the most complete of its day. Hevelius used a quadrant for this and was the last astronomer to do major observational work without the aid of a telescope.
Edmond Halley (1656 - 1742)
Edmond Halley made enormous contributions to almost every branch of physics and astronomy. Using his knowledge of geometry and historical astronomy, Halley linked the comet sightings of 1456, 1531, 1607 and 1682 to the same object which he correctly predicted would return in 1758. Halley would be long dead by then, which is why not everyone took his prediction seriously, but the comet was named after him nonetheless. He died in 1742 but the comet is his lasting legacy.
William Herschel (1738 - 1822)
William Herschel, the discoverer of Uranus, was a renowned observational astronomer of the 18th century. King George III, who was a strong supporter of scientific enquiry, employed him on a salary of £200 a year and financed the construction of several large telescopes. Herschel found Uranus in 1781, which brought him worldwide fame, followed by two of its moons in 1787. He also made about 400 telescopes, culminating in the enormous 40ft (12m) reflector.
John Herschel (1792 - 1871)
John was the son of William Herschel. He studied mathematics as Cambridge and began to assist his father in 1816. In 1834 he went to the observatory at the Cape of Good Hope to survey the southern skies and, while there, discovered no fewer than 2,000 nebulae and 2,000 double stars. John found himself in the midst of controversy in 1835 when the New York Sun newspaper spun a hoax to boost its sales claiming that he had found animals living on the Moon.
William Huggins (1824 - 1910)
Huggins founded astronomical spectroscopy, being the first to make intensive 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 also proved that emission nebulae are glowing clouds of gas.
Ejnar Hertzsprung (1873 - 1967)
Hertzsprung discovered the two main groupings of stars - the luminous giants and supergiants, and the dwarfs now known as main-sequence stars. Henry Norris Russell made the same discovery independently. Both created diagrams to show the grouping of these stars, which are today known as Hertzsprung-Russell diagrams. Hertzsprung also measured the distances to several variable stars, which he then used as a measuring stick to find the distance of the Small Magellanic Cloud.
Edwin Hubble (1889 - 1953)
Hubble, who trained as a lawyer, 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 achievement. When he compared these distances to redshift measured by others, he found that a galaxy's distance is proportional to its velocity. He thus confirmed the idea of an expanding Universe, which is fundamental to cosmology.
Gerard Kuiper (1905 - 1973)
Kuiper, the most distinguished 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 usually best remembered for his prediction of enormous swarms of comet cores and small icy bodies beyond Neptune: the Kuiper Belt.
Sir Bernard Lovell (1913 - 2012)
Sir Bernard Lovell began his scientific career in cosmic ray research at Manchester University; during the war he was a radar pioneer. Subsequently, he became interested in the new science of radio astronomy and put forward the idea of building a fully 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!