Pluto was discovered in 1930 by the astronomer Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona. For many years Pluto was considered to be the ninth and outermost planet in our solar system. Pluto itself is only about two thirds the size of our own Moon.
It wasn’t until 1978 that astronomer Jim Christy discovered a large moon orbiting Pluto. The moon was named Charon. Charon is about half the size of Pluto. It’s now known that there are 5 moons orbiting Pluto. The New Horizons flyby mission determined in 2015 that these are the only moons of Pluto.
The collection of 5 moons around Pluto, along with the large size of the moon Charon compared to Pluto, create a complex and delicately balanced orbiting system. The center of mass of the Pluto-Charon orbit lies in the space between the two bodies, and they swing around this point in space in an orbit that is on its side when compared to the plane of the solar system.
As modern telescopes continued to improve, astronomers began to discover more of these small planets similar to Pluto in a vast reservoir that exists beyond Neptune. These rocky and icy bodies orbit the Sun roughly in the same plane as the planets. The region is now known as the Kuiper Belt, named after the Dutch astronomer Gerard Kuiper who proposed its existence. Many of the larger objects orbiting there are referred to as dwarf planets. More dwarf planets have now been discovered in the Kuiper Belt, and many more will be discovered by future astronomers. These discoveries have led to Pluto being “demoted” in status to a dwarf planet, which astronomers say is more consistent with the modern understanding of the solar system.
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