Top 10 Astronomers

Sic itur ad astra: To commemorate the Kepler mission, NASA’s first mission to search for worlds that could potentially host life, here is a post about the greatest astronomers in history, chronologically: 


Tycho Brahe (1546-1601) 


An alchemist and an astronomer, Tycho Brahe known more for the sheer volume of his observations than for his discoveries. Being a Danish nobleman, he had his own observatory/castle built by his king, from which he observed all known celestial objects. Although it has been down previously before, Brahe measured the Earth’s axial tilt more accurately than ever before. Brahe was not a Copernican, however; he proposed a stem in which the Sun orbited the Earth while the other planets orbited the Sun, while denouncing Coperinicus’ transparent rotating spheres. He observed a supernova now known as “Tycho’s supernova” and made the most precise observations of stellar and planetary positions. His death itself was surrounded in mystery, but his records of planetary motions enabled his protege (and alleged killer) Kepler to discover the laws of planetary motion and dispel the heliocentric theory for once and for all. Above, the monument to Brahe and Kepler in Prague, Czech Republic. 

Galileo Galilei (1564-1642)

A true Renaissance man, Galileo published his initial telescopic astronomical observations in 1610 in a short treatise entitled Sidereus Nuncius (Starry Messenger). In the last portion of Sidereus Nuncius, Galileo reported his discovery of four objects that appeared to form a straight line of stars near Jupiter–four first Jovian Moons. Io, Europa, Callisto and Ganymede were originally named after the members of the Medici family (Galileo’s patrons) but later renamed as Galilean satellites. By proving Venus exhibited a full set of phases similar to that of the Moon, Galileo refuted Ptolemaic pure geocentric model. Galileo also observed the planet Saturn but mistook its rings for planets, thinking it was a three-bodied system. Galileo was one of the first Europeans to observe sunspots, lunar mountains and craters and also stated that Milky Way was made up of stars, instead of nebulous as previously thought. He even observed the planet Neptune but marked it down as a dim star, thus delaying the discovery for more than three centuries.  Above: the Inquistion confronts Galileo on his beliefs. 

Giovanni Cassini (1625-1712)


An astrologer as well as an astronomer, Giovanni Cassini served as the Count Astronomer/Astronomer to King Louis XIV of France. During his time at the Court of the Sun King, he accurately measured the size of France for the first time, which turned out to be considerably smaller than expected. The amused king noted that Cassini had taken more of his kingdom from him than he had won in all his wars. Along with Robert Hooke, Cassini was credited with the discovery of the Great Red Spot in Jupiter. He was also the first to observe four of Saturn’s moons. Those moons he once named Sidera Lodoicea (Louisean Stars after the Latinized name of King Louis), are now known as Iapetus, Rhea, Tethys and Dione. Above: Cassini (arrowed) arrived at the Sun King’s court. 

Christiaan Huygens (1629-1695) 
Like many scientists of his days, Christopher Huygens is known for the discovery of many breakthroughs. In his annus mirabilis of 1655, he designed a refracting telescope, discovered the first of Saturn’s moons (Titan), formulated that Saturn is surrounded by a solid ecliptic ring, and discovered and sketched the Orion Nebula. He also observed planet Mercury’s solar transit in 1661, and wrote two monumental books Systema Saturnium and Cosmotheoros. In the latter, he speculated about life on the other planets, and imagined a universe brimming with life. A fellow of the Royal Society and of the French Academy of Sciences, he worked together with Giovanni Cassini at the newly completed Paris Observatory (opened in 1671) under the patronage of Louis XIV.  Above: King Louis and Minister Colbert visits Director Cassini and Huygens at the newly completed Paris Observatory in 1671. 

Charles Messier (1730-1817) 


Although many listings in his eponymous catalogue were discovered by his assistant Pierre Mechain, and many are not organized scientifically (by type, or location), Charles Messier left behind a lasting standard for astronomy. In 1774, he published first of his astronomical catalogues, which contained the observational data for 45 celestial objects. By the time the final version of the catalogue was published in 1781, the list of Messier objects had grown to 103. A comet hunter, Messier complied his “Catalogue des Nébuleuses et des Amas d’Étoiles” (“Catalogue of Nebulae and Star Clusters”) in frustration from his list of non-comet objects that frustrated his hunt for the comets. 

William Herschel (1738-1822)


A Hanoverian émigré to England, William Herschel was obsessed with music and telescopes since young. Working as a lowly music teacher in Bath, he discovered the planet Uranus in 17981 using a small homemade telescope. He named the new planet Georgium Sidus (Georgian Star) after his king, George III, but the French vocally protested it, and the planet was known as ‘Herschel’ until the name ‘Uranus’ was universally adopted. Handsomely rewarded in England and knighted, Herschel became the King’s Astronomer, and retired to become a telescope maker–his primary hobby. He, however, coached his sister Caroline (above) to become one of the greatest astronomers of her day. Caroline Herschel became the first woman to discover a comet. William himself went to measure the Sun’s motion, and to become discoverer of the  sunspots and the infrared range of sunlight. 

Thomas James Henderson (1798-1844) 


The first Astronomer Royal for Scotland, Thomas Henderson was the first person to measure the distance to a star (Alpha Centauri, the nearest stellar system to Earth). Working at the British Observatory at the Cape of Good Hope, he made a number of stellar observations for which he is mainly remembered today. The 1830s version of the “space race” was to be the first person to measure the distance to a star using parallax, a task which is easier the closer the star. Doubts about the accuracy of his instruments kept him from publishing, but after he was beaten to the punch by Frederic Wilhelm Bessel (who measured 10.4 light years to Sirius) in 1838, Henderson published his results, thus claiming his rightful spot in history.  

William Lassell (1799-1880) 


Although he is today remembered as the pioneer of the age of “Grand Amateurs” in astronomy, WIlliam Lassell appeared as if he is least suited for this avocation–he is a career beer brewer from Liverpool. When “Le Verrier’s Planet” (later to be named Neptune) was first observed in Berlin, Lassell used the new planet’s co-ordinates, published in The Times, to discover its satellite (Triton) and its ring. Within a month of Neptune’s discovery (and before the planet was even named), Lassell announced his discoveries to The Times. Two years later in 1848, he independently discovered Hyperion (a moon of Saturn) and in 1851, he discovered Ariel and Umbriel, two moons of Uranus. Lassell also pioneered the use of an equatorial mount and built a 48-inch (1,200 mm) telescope on Malta. 


Urbain Le Verrier (1811-1877)


Best remembered for his discovery of planet Neptune, le Verrier was a mathematician first. From the illustrious Director chair at the Paris Observatory (its first director was Cassini, no less), Le Verrier predicted the existence of a then unknown Transuranian planet using only mathematics and astronomical observations of the known planet Uranus. Unknown to Le Verrier, similar calculations were made by an Englishman John Couch Adams, but le Verrier announced his prediction two days before Adams’s final solution. Encouraged greatly by his success, le Verrier went on to predict an unknown planet closer to the Sun than Mercury, which he tentatively named Vulcan. This prediction became his long-lasting, and controversial legacy, triggering a wave of false detections, which lasted until 1915, when Einstein explained Mercury’s anomalous motion with his theory of general relativity.  


Clyde Tombaugh (1906-1997)


On the New Horizon spacecraft, launched for a flyby of Pluto in 2014, is a container inscribed: “Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system’s ‘third zone’. Adelle and Muron’s boy, Patricia’s husband, Annette and Alden’s father, astronomer, teacher, punster, and friend: Clyde W. Tombaugh (1906-1997).” Best known for discovering the planet/dwarf planet Pluto, Clyde Tombaugh was working at the Lowell Observatory in Arizona while he was given the job to search for the Planet X (the trans-Neptunian planet), which had been predicted by the observatory’s founder Percival Lowell and William Pickering. Using the photographers taken by the observatory’s 13-inch astrograph, he found Planet X on Tuesday, February 18, 1930, using images taken in January of the same year. The name “Pluto” was suggested by an English schoolgirl, which was chosen because it was after the Roman god of the Underworld (who was able to render himself invisible) and because Percival Lowell’s initials PL formed the first 2 letters. 


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