The definition of planet has comprised many different things. Early use of the term was never strict and its meaning has blurred to include or exclude a variety of objects. By the end of the 19th century, the word planet had a more firm definition: it applied only to objects in the
Solar System, a number small enough that any differences could be dealt with on an individual basis. After 1992 however, astronomers began to discover many additional objects beyond the orbit of
Neptune, as well as hundreds of
extrasolar planets. These discoveries not only increased the number of potential planets, but expanded their variety and peculiarity. The issue of a clear definition for planet came to a head in 2005 with the discovery of the
trans-Neptunian objectEris, a body larger than the smallest then-accepted planet,
Pluto. In its 2006 response to the discovery, the
International Astronomical Unionreleased its decision on the matter. Its definition, which applies only to the Solar System, states that a planet is a body that orbits the
Sun, is
massive enough for its
own gravity to make it round, and has "
cleared its neighbourhood" of smaller objects around its orbit. Under this new definition, Pluto, along with the other trans-Neptunian objects, does not qualify as a planet. (
more...)
... that though it was decided as early as 1882 to install a lighthouse at Contendas Point on
Terceira Island, the Ponta das Contendas Lighthouse was not built and inaugurated till almost 52 years afterwards?
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