Neptune's first orbit: a turning point in astronomy
As Neptune nears a historic orbit around the Sun, Robin McKie recalls the dramatic story of how the icy world was discovered
Neptune rising: although discovered in 1846, we didn’t get a glimpse of this alien world until Voyager 2 swept past in 1989. Photograph: Corbis
Astronomers will celebrate a remarkable event on 11 July. It will be exactly one year since the planet Neptune was discovered. Readers should note a caveat, however. That year is a Neptunian one. The great icy world was first pinpointed 164.79 years ago – on 23 September 1846. And as Neptune takes 164.79 Earthly years to circle the sun, it is only now completing its first full orbit since its detection by humans. Hence those anniversary celebrations.
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