Event of 1899: Phoebe, the ninth-known moon of Saturn, is discovered by U.S. astronomer William (1899)

In March 1899, U.S. astronomer William Henry Pickering identified Phoebe, Saturn's ninth-known moon, by analyzing photographic plates captured in August 1898 at the Boyden Station near Arequipa, Peru. This event marked the first time a natural satellite was discovered photographically, establishing a new method for astronomical observation.

Episodes

Background and detail

Background. Phoebe is the most massive irregular satellite of Saturn, with a mean diameter of 213 km. The satellite's retrograde orbit distinguishes it from other irregular moons, and it remained Saturn's outermost known moon for over a century until smaller moons were found in 2000.

Discovery. William Henry Pickering discovered Phoebe on 18 March 1899. The discovery resulted from analyzing photographic plates taken starting on 16 August 1898 at the Boyden Station of the Carmen Alto Observatory near Arequipa, Peru, by DeLisle Stewart. This was the first natural satellite to be discovered photographically.

Significance. The discovery marked a milestone in astronomy as the first photographic detection of a natural satellite. Phoebe's orbit is significantly different from those of other irregular moons, and it remained the outermost known moon of Saturn for more than 100 years.

People involved

Sources

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