Neptune: History

Neptune was formed around 4.5 billion years ago, along with the other planets in the solar system. Neptune is the fourth largest planet, after Jupiter, Saturn, and Uranus. Almost identical in size to Uranus, its sister planet, Neptune was formed, along with the other planets, from the primordial solar nebula. While the larger planets (Jupiter and Saturn) received the lion’s share of the nebula’s hydrogen and helium, Uranus and Neptune appear to have received only rock and ice.

Timeline

1788	Discrepancy between Uranus’s position and orbital tables
1834	Hussey proposes another planet beyond Uranus, is rebuffed
1836	Existence of a trans-Uranian planet generally accepted
1843	Adams outlines plan to calculate position of mysterious planet
1845	Adams solves problem, confirming the existence of the exterior planet; Le Verrier presents a second paper on Uranus’s motion, attributing its rotational irregularity to an eighth planet
1846	Challis begins search for mysterious planet, sees it but not does not recognize it; Galle and d’Arrest of the Berlin Observatory find the planet after a brief search, consensus is to name it Neptune, not “Le Verrier”
1847	Lassell’s discovery of Neptune’s moon Triton confirmed
1949	Second moon of Neptune, Nereid, discovered by Kuiper
1977	Voyager 2, NASA space probe, launched
1989	Voyager 2 flies by Neptune, discovering most of what is known of Neptune today