Source : nationalgeographic
The discovery of the eighth planet Neptune was one of the high points in the development of the theory of gravity. In 1781, William Herschel, an amateur musician and astronomer, accidentally discovered the seventh planet Uranus. Uranus was observed by chance a century ago. but none of these early sightings recognized it as a planet; rather, it was simply recorded’ as a star. Herschel’s discovery indicated that there might be planets in the solar system that are too faint to be visible to the naked eye, but ready to be spotted with a telescope if we know where to look.
Until 1790, an orbit for Uranus was calculated based on observations of its motion in the decade after its discovery. But even after considering the disruptive effects of Jupiter and Saturn, it was discovered that Uranus was not moving in an orbit that exactly coincided with previous observations since 1690. By 1840, the discrepancy between the observed positions of Uranus and those predicted by its calculated orbit was about 0.03°, an angle that is barely noticeable to the naked eye, but which is still greater than the probable errors in orbit calculations. In other words, Uranus just didn’t seem to be in the orbit Newton predicted.Theory.
In 1843, John Couch Adams, a young Englishman who had just graduated from Cambridge, began a detailed mathematical analysis of the irregularities in the motion of Uranus to see if they could be caused by the attraction of an unknown planet. away from the Sun as Uranus, and then determines the mass and orbit it needed to have to account for the deviations in Uranus’ orbit. In October 1845, Adams presented his results to George Airy, the British Royal Astronomer, informing him where the sky was’ not immediately tracked. We now know that Adams’ predicted position for the new body was correct within 2 °, but Airy did not immediately follow suit for various reasons.
Meanwhile, the French mathematician Urbain Jean Joseph Le Verrier, unfamiliar with Adams or his work, attacked the same problem and published his solution in June 1846. Airy found that the position predicted by Le Verrier for the unknown planet was in 1 ° with it Of Adams agreed, suggested James Challis, director of the Cambridge Observatory, begin looking for the new object. The Cambridge astronomer, who had no current star maps of the Aquarian region where the planet was predicted, recorded the positions of all faint stars. Stars that he could observe there with his telescope. Challis’ plan was to repeat such graphs at intervals of several days, in the hope that planet would be distinguished from a motion of a star. Unfortunately he was negligent in examining his observations; Although he had actually seen the planet, he did not recognize it.
About a month later, Le Verrier suggested to Johann Galle, an astronomer at the Berlin observatory, that they search for the planet. Galle received the letter from Le Verrier on September 23, 1846 and found and identified the planet as he had new chart of Aquarian region. That night he was less than a degree from the position LeVerrier had predicted. The discovery of the eighth planet now known as Neptune (the Latin name for the god of Estosa) was a great triumph for the theory of gravity as it dramatically confirmed the theory of gravity. General validity of Newton’s laws. The honor for the discovery is duly shared by mathematicians Adams and Le Verrier.
It should be noted that the discovery of Neptune came as no complete surprise to astronomers, who had long suspected the existence of the planet due to the “disobedient” movement of Uranus. On September 10, 1846, two weeks before Neptune was actually found, John Herschel, son of the discoverer of Uranus, commented in a speech to the British Association: “We [the new planet] look like Columbus see America from coast of Spain ” . Their movements were felt with a little less certainty than before along the long-range line of our analysis with a certainty slightly lower than the ocular demonstration.
This discovery was a great advance in combining Newton’s theory with detailed observations. This work continues in our time with the discovery of planets around other stars.
