English mathematician and theoretical astronomer John Couch Adams was born on June 5th, 1819, near Launceston, in Cornwall. Under the guidance of his maternal uncle, the Rev. John Couch Grylls, and using the facilities of the Mechanics’ Institute, Devonport, to further his studies privately, at the age of 2o he entered St. John’s College, Cambridge. He excelled at mathematics to the point of achieving the exalted position of Senior Wrangler (nothing to do with cows or denim, it’s the top scoring maths graduate of the year) in 1843.
Two years previously he had already begun to be intrigued by the possibility of a planet beyond Uranus, as the following nineteenth century “note to self” shows:
“Formed a design . . . of investigating . . . the irregularities in the motion of Uranus, . . . in order to find whether they may be attributed to the action of an undiscovered planet beyond it . . . “
Adams’ study of the perturbations of Uranus’ motion first led him to conclude that an unknown planet beyond Uranus, located at double the distance from the Sun, might exert the necessary influence on Uranus if it was big enough, and in the right place. Following his obtaining more precise observations from the Astronomer Royal, a more refined prediction of how to locate the eighth planet was made, which Adams took to Greenwich Observatory and left for the attention of the aforementioned Astronomer Royal.
At the same time, Urban Le Verrier had also been on Neptune’s trail, and had predicted a location within one degree of that determined by Adams. Unfortunately for the reputation of British astronomy, the lack of accurate star charts meant that looking for an object moving against the background involved a painstaking wait for two lots of observations to be undertaken, recorded and compared. But Le Verrier’s calculations were in the hands of Dr Johann Galle at the Berlin Observatory and, despite beginning his search two months later than the British team (led by James Challis), with typical German efficiency he discovered the planet on the first night of observation, through the rather obvious method of having accurate star charts to hand.
2002 – Discovery of trans-Neptunian object 50000 Quaoar. Potentially a dwarf planet (it has a diameter of about 1000 km, but more information on its mass is needed before a decision can be made) I’m mentioning it mainly because 50000 is a nice round number, and partly because Quaoar was the first TNO to be detected directly from Hubble Space Telescope images.
1980 – Launch of Soyuz T-2.