Astronomy and Exploration (1700-1800s)
The first correct theories of how the Solar System formed appeared in the 1700s. In 1734, Swedish physicist, Emanuel Swedenborg suggested that the planets could have once originated from the mass as the Sun and, in 1755, German philosopher Immanuel Kant argued that the Solar System had once been a large cloud of gas, a nebula. This theory was popularised by French astronomer Pierre-Simon Laplace's nebula hypothesis, published in 1796. Kant was also one of the first to argue that some of the nebula which had been discovered could be separate 'island universes', or galaxies.
In 1750, French astronomer Nicolas Louis de Lacaille observed fourteen new constellations from his observatory on the peak of Table Mountain in South Africa. Unlike Keyser and Houtman who had kept to the Greek tradition of naming constellations after animals and people, Lacaille named most of his constellations after scientific and artistic instruments, which he believed to reflect the spirit of the time. These were; The Air Pump, The Net, The Laboratory Furnace, The Microscope, The Telescope, The Clock, The Painter's Easel, The Sculptor's Workshop, The Sculptor's Chisel, The Compass Box, The Compasses, The Carpenter's Square, The Octant and finally, The Mensa which is Latin for table and refers to Table Mountain. Lacaille was one of the first to break Ptolemy's Argo Navis constellation into the three parts we use today. He also eliminated the constellation Robur Carolinum, the Charles Oak, first introduced by English astronomer Edmund Halley to honour King Charles II.
The Star Garden
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The Air Pump The Microscope
French astronomer Pierre Charles Le Monnier added a final constellation in 1776, the Turdus Solitarius. It was debatable which bird it was supposed to represent. In 1806, English physicist Thomas Young renamed it the Mocking Bird and sixteen years later, Scottish artist Alexander Jamieson changed it to Noctua, the owl.
The known size of the observable universe doubled in 1781, when German-British astronomer William Herschel discovered Uranus. Herschel was also the first to map the shape of the Milky Way. He did this by assuming that brighter stars are closer and duller ones are further away. He saw that the Sun is moving towards the constellation of Hercules and suggested that the galaxy has a central 'Sun' which the Solar System orbits.
Herschel's galaxy
The 18th century ended with another astronomical measurement. In 1797, English physicist Henry Cavendish weighed the Earth. He did this by measuring the faint gravitational attraction of a number of objects in the laboratory. Once he could compare the different forces exerted by different masses, he could calculate Newton's proportionality constant and use it to work out the mass of other objects. The mass of the Earth was calculated to be about 6x10^24 kilograms (this is six million, billion, billion), which is very close to the value accepted today.
The 19th century began with the discovery of the largest asteroid, Ceres, which was discovered by Italian astronomer Giuseppe Piazzi in 1801. German astronomer Johann Elert Bode had already predicted that there should be a planet there and Ceres was accepted as such for the next fifty years. When other asteroids were discovered it was suggested that what would have been a planet had been prevented from forming by the gravitational pull of Jupiter.
Just over fifty years since Herschel's discovery, the known size of the universe increased once again, this time by a factor of over 8000. This occured shortly after German astronomer Friedrich Bessel became the first to measure stellar parallax in 1838. Stellar parallax is the apparent movement of the stars due to the Earth's change in position and is what Bradley was looking for when he discovered stellar aberration. Bessel knew that if he could measure the angle that the stars appeared to move, then he could determine how far away they are using trigonometry. Stars that are closer should appear to move more than those that are very far away. Bessel determined that 61 Cygni is about 10.4 light years away, this was quickly followed by Russian astronomer Friedrich Georg Wilhelm von Struve's announcement that Vega is about 26 light years away. Both were correct to within one light year (Lang, 2006, pp.23).
In 1845, Irish astronomer William Parsons had described the spiral structure of Andromeda, and in 1888, Welsh astronomer Isaac Roberts was the first to photograph it.
Isaac Roberts' photograph of Andromeda
German astronomer Johann Galle was the first to observe Neptune in 1846, following calculations made by French astronomer Alexis Bouvard and French mathematician Urbain Le Verrier. Its largest moon, Triton was discovered two and a half weeks later by English astronomer William Lassell. Our knowledge of the Solar System expanded once again when American astronomer Asaph Hall discovered the moons of Mars, Phobos and Deimos in 1877.
References
Lang, K.R., 2006, 'A companion to astronomy and astrophysics: chronology and glossary with data tables', Springer, New York, pp.23