Q2 Astronomer Biography

Nicolas Lacaille

            Nicolas Louis de Lacaille was a prominent French astronomer who lived during the 18^th century. Born on the 29^th of December, 1713 in Rumigny, France, Lacaille attended school in what is now known as Mantes-la-Jolie, and eventually went on to study philosophy and rhetoric at the Collège de Lisieux, and then theology at the Collège de Navarre. After graduating, Lacaille became an Abbé, a position in the Catholic Church. Lacaille worked in a few universities as a professor throughout his life, and one of his earliest accomplishments was the correct re-measurement of the French arc of the meridian. For this, a pyramid was built in his honor.

            One of the primary desires of Lacaille was to measure the distances of the planets trigonometrically. He wished to travel to the Cape of Good Hope, at the Southern tip of Africa. His voyage was sanctioned by Roland-Michel Barrin de La Galissonière, a French governor. Lacaille stayed there for two years, making observations on a nightly basis. His observations resulted in a thorough catalog of roughly 10,000 stars. In addition, he also observed and recorded 42 nebulous objects. Along with these catalogs, Lacaille was able to successfully determine the parallax of the moon and the sun, using Mars as an intermediary. This tedious work required simultaneous observation from a partner of his in an observatory in France, Jérôme Lalande. His astronomical catalogs were published posthumously, resulting in 14 newly discovered constellations, which have since become standard. During his 2 year stay in the Cape of Good Hope, Lacaille also measured the radius of the Earth in the Southern Hemisphere. Being a very meticulous and astute calculator and mathematician, Lacaille used triangulation to determine these measurements.

            During his return to France, Lacaille realized how difficult it was to make measurements and determining positions while at sea. On his return to Paris, he produced a set of tables of the Moon’s position that was accurate enough to use for determining time and longitude by Lunars, or Lunar distances. In addition to these impressive calculations, Lacaille also produced a table of eclipses that occurred, spanning 1800 years. A colleague of his, Jérôme Lalande, said of Lacaille that during a relatively short life, he was able to make more calculations than any other astronomer until then. He also stated that the quality of his work was just as high as the quantity, and that his strong, respectable personality earned him a great deal of universal admiration.   

            In Paris in 1757, Lacaille published his Astronomiae Fundamenta Novissimus, which contained a list of 400 bright stars with their positions corrected due to atmospheric aberration. He also carried out calculations on the orbits of comets, and was actually responsible for giving Halley’s Comet its name. The crater Lacaille on the Moon was named in his honor, and the asteroid 9135 Lacaille was named after him as well. In addition, a 60 centimeter telescope in Reunion Island will be named Lacaille Telescope due to his studies of the Southern Hemisphere sky.