What are the Astronomers, who helped enhance our understanding of the cosmos?

We have always been looking up, peering into the sky, trying to find answers to the many questions about the universe. Many astronomers have tried to unravel the mysteries of the universe. From believing that Earth was flat and the planets revolved around it, we have come a long way. Let’s take a look at some of history’s greatest astronomers who helped enhance our understanding of the Cosmos.

From believing that the Earth was flat and the planets revolved around it, we have come a long way.Some 2000 years ago, when it was widely believed that the world was flat, Greek mathematician and astronomer Eratosthenes (276 BC-194 BC) calculated the Earth’s circumference. In those days, the very act of coming up with scientific thoughts which were at odds with the ones in existence was not encouraged. The theory that the Earth revolved around the Sun was itself considered heretical by the religious and after a trial, Italian astronomer Galileo Galilei was kept under house arrest until his death. Polish astronomer Nicolaus Copernicus didn’t publish his magnum opus “De revolutions orbium coelestium” (On the Revolutions of the Heavenly Spheres) until he was on his deathbed. Let’s take a look at some of history’s greatest astronomers who threw new light on the cosmos.


 Astronomer and mathematician Claudius Ptolemy authored several scientific teas and is noted for his Ptolemaic system. It was a geocentric (Earth-centred) model of the universe, where the sun, stars, and other planets revolved around Earth. This model was used for a long period, for over 1200 years, until the heliocentric view of the solar system was established. Although his model of the universe was wrong, his work and the scientific texts he authored helped astronomers make predictions of planetary positions and solar and lunar eclipses. “The Almagest, a comprehensive treatise on the movements of the stars and planets, was published in the 2nd Century. It is divided into 13 books. This manual served as the basic guide for Islamic and European astronomers. He also catalogued 48 constellations. 


 Nicolaus Copernicus changed the way scientists viewed the solar system. Back in the 16th Century, he came up with a model of the solar system where the Earth revolved around the Sun: it was the revolutionary heliocentric model. He removed Earth from the centre of the universe and replaced it with the Sun! He also didn’t believe in the Ptolemaic model of the planets travelling in circular orbits around the Earth. He also explained the retrograde motion of the planets (retrograde motion is when planets appear to move in the opposite direction of the stars). When the Polish astronomer was 70, he published his book “De Revolutions Orbium Coelestium” (“On the Revolutions of the Heavenly Spheres”), on his deathbed. It took over a century for his idea to gain credence.


Optical astronomy began with Galileo Galilei. Born in Italy, Galilei is credited with creating the optical telescope. In fact, what he did was improve upon the existing models. He came up with his first telescope in 1609, modelling it after the telescopes produced in other parts of Europe. But here is the catch. Those telescopes could magnify objects only three times. Galileo came up with a telescope that could magnify objects 20 times. He then pointed it towards the sky, coming up with the greatest discoveries ever. He discovered the four primary moons of Jupiter which are referred to as the Galilean moons. He also discovered the rings of Saturn. Even though the theory of Earth circling the Sun had been around since Copernicus’ time, when Galileo defended it, he was kept under house arrest till the end of his lifetime.


Danish astronomer Johannes Kepler modified the Copernican view of the solar system and changed it radically. He deduced that the planets travelled in elliptical orbits, one of the most revolutionary ideas at the time, replacing Copernicus view that they travelled in circular objects. He came up with three revolutionary laws involving the motions of planets these three laws make him a towering figure in astronomy. Kepler also observed a supernova in 1604. It is now called Kepler’s Nova.

EDMOND HALLEY (1656-1742)

“Halley’s comet is perhaps a term you would have heard quite often. English astronomer Edmond Halley never saw the comet named after him. Officially called 1P/Halley, Halley’s  comet  is a periodic comet that passes by the Earth once every 76 years (roughly). This famed comet will return in 2061. It was Halley’s mathematical prediction of the comet’s return that made him a towering figure among the list of astronomers. He said that the comet that appeared in 1456, 1531, 1607, and 1682 were all the same and that it would return in 1758. Halley was never around to witness this, but the world saw the comet and its return. The comet was later named in his honour. One of the earliest catalogues of the southern sky was also produced by Halley. In 1676, he sailed to the island St. Helena, South Atlantic Ocean. There he spent a year measuring the position of stars and came up with the first catalogue of the southern sky! Seen here is a painting of the astronomer. 


Musician-tumed astronomer William Herschel started exploring the skies with his sister Caroline quite late in his career but eventually, he compiled a catalogue of 2.500 celestial objects The German astronomer discoverest the planet Uranus and several moons of other planets it was during his mid 30s that he startet looking up and exploring the cosmos In 1759. Herschel left Germany and moved to England where he started teaching music When Herschels interest in astronomy grew, rented a telescope. He then went ahead and built himself a large telescope to watch the celestial bodies. His sister Caroline assisted him until Herschel’s death and also became the first woman to discover a comet. She eventually discovered eight of them. When Herschel found a small object in the night sky, he explored further and found out that it was a planet. The Uranus was thus discovered. He was knighted by the monarch after the discovery and was appointed the court astronomer. Following this he gave up his music career and devoted himself to the skies. He found the moons of Uranus and Saturn Craters on the moon. Mars and Mimas (Saturn’s moon) are named after the astronomer.


Known as the “census taker of the sky, American astronomer Annie Jump Cannon made stellar contributions to the field of astronomy. She classified around 3,50,000  stars manually. At a time when gender representation in astronomy was  skewed. Cannon with her impeccable contributions inspired many women to pursue astronomy. During that time, stars were classified alphabetically, from A to Q. based on their temperatures. She built a new classification system with ten categories and forever changed the way scientists classified stars by developing the Harvard system which is in use even today.

CARL SAGAN (1934-1996)

American astronomer Carl Sagan was not just a science poster boy but he was one of the most influential voices in the scientific  realm  who  made the cosmos a subject of interest for the masses. Sagan played a huge role in in the American space program. He popularised astronomy and through his talks and books motivated many to become sky watchers. He also founded the Planetary Society, a non-profit that is focussed on advancing space science and exploration. He was a professor of astronomy and space sciences and director of the Laboratory for Planetary Studies at Cornell University. His contributions include explaining the high temperatures of Venus and the seasonal changes on Mars. His book “Cosmos” is a bestseller that was also turned into a television show (hosted by Sagan) which was watched by a billion people in 60 countries. He also wrote a science fiction novel “Contact” which was adapted to the screen.

Picture Credit: Google

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