SIDUS GEORGIIUM, in astronomy, a new primary planet, discovered by Dr Herschel in the year 1781. By most foreign, and even by some British philosophers, it is known by the name of Herschell, an honour which is due to the discoverer. As the other planets are distinguished by marks or characters, the planet Herschel is distinguished by an H, the initial letter of the discoverer's name, and a cross to show that it is a Christian planet. From many calculations of our best astronomers
Siege mers and mathematicians, says Dr Herschel, I have collected the following particulars, as most to be depended upon.
| Place of the node | - | 2d 11d 49' 30" |
| Inclination of the orbit | - | 43' 35" |
| Place of the perihelion | - | 172d 13' 17" |
| Time of the perihelion passage | Sep. 7. 1799 | |
| Eccentricity of the orbit | .82034 | |
| Half the greater axis | 19.07904 | |
| Revolution | 833364 siderial years. | |
From my own observations on this planet's apparent diameter, which I have found cannot well be less than 4", nor indeed much greater, we infer, that its real diameter is to that of the earth as 4,454 to 1; and hence it appears to be of very considerable bulk, and, except Saturn and Jupiter, by far the largest of the remaining planets. Its light is of a bluish-white colour, and in brilliancy between that of the Moon and of Venus. With a telescope which magnifies about 300 times, it appears to have a very well defined visible disk; but with instruments of a small power, it can hardly be distinguished from a fixed star of between the sixth and seventh magnitude. In a very fine clear night, when the moon is absent, it may also be seen by the naked eye.