Changes

According to the [[International Astronomical Union]], it no longer qualifies as a [[planet]] because it has not cleared its orbit of other objects. But the IAU decided that under circumstances at least one observer calls suspicious. (See below.)

According to the [[International Astronomical Union]], it no longer qualifies as a [[planet]] because it has not cleared its orbit of other objects. But the IAU decided that under circumstances at least one observer calls suspicious. (See below.)

In 2015 the U.S> spacecraft ''New Horizons'' passed through the Plutonian system. The [[United States]] thus became the first nation-state to complete a reconnaissance of the original nine named planets. ''New Horizons'' found many signs that are ''not'' consistent with the conventional favored theory of Pluto's origin. Pluto has mountains that have not eroded. That suggests the body is active. Pluto also has a frozen lake of carbon monoxide that no one has yet been able to explain.

In 2015 the U.S. spacecraft ''New Horizons'' passed through the Plutonian system. The [[United States]] thus became the first nation-state to complete a reconnaissance of the original nine named planets. ''New Horizons'' found many signs that are ''not'' consistent with the conventional favored theory of Pluto's origin. Pluto has mountains that have not eroded. That suggests the body is active. Pluto also has a frozen lake of carbon monoxide that no one has yet been able to explain.

== Discovery ==

== Discovery ==