Technically, there was never a scientific definition of the term Planet before When the Greeks observed the sky thousands of years ago, they discovered objects that acted differently than stars. These points of light seemed to wander around the sky throughout the year. We get the term "planet" from the Greek word "Planetes" - meaning wanderer.

In the 1600's scientists began to use telescopes to view our solar system. As technology got better, scientists discovered more planets orbiting our Sun such as Uranus in 1781, Neptune in 1846 and Pluto in Then, in 1991, advances in telescope technology enabled scientists to discover many more objects in a disk-shaped cloud beyond Pluto called the Kuiper Belt. These objects were classified as Kuiper Belt Objects (KBO) partly because they are smaller than Pluto. This classification of KBO seemed to work fine as long as objects weren't bigger than Pluto.

It was the recent discovery of an object larger than Pluto within the Kuiper Belt that changed everything. Is this object, now named Eris, our 10th planet since it is larger than Pluto? This discovery and the naming of this new object prompted the IAU to discuss a scientific definition for the term planet. What if Eris is given planet status? Then our solar system could grow to dozens of planets as more and more Kuiper Belt Objects are discovered. Try remembering all those planet names. But if Eris is not a planet, then is Pluto still a planet?

Astronomers of the International Astronomical Union (IAU) voted on and passed the first scientific definition of a planet in August According to this new definition, an object must meet three criteria in order to be classified as a planet.

1.It must orbit the Sun. 2.It must be big enough for gravity to squash it into a round ball. 3.It must have cleared other objects out of the way in its orbital neighborhood. To clear an orbit, a planet must be big enough to pull neighboring objects into the planet itself or sling-shot them around the planet and shoot them off into outer space.

The problem for Pluto is the fact that its orbit is in the Kuiper Belt along with 43 other known Kuiper Belt Objects (KBOs).

1.It is in orbit around the Sun 2.It has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape 3.It has not cleared the neighborhood around its orbit. 4.It is not a satellite (a moon)

Pluto is the second closest dwarf planet to the Sun Discovered in 1930 by Clyde W. Tombaugh in Flagstaff. It was considered the 9 th planet until It is the second largest dwarf planet. Pluto Day = 6.4 days Pluto Year = 248 years

Pluto has 5 moons: Charon, Styx, Nix, Kerberos and Hydra Charon is the largest of the moons. Charon is also so large that Pluto-Charon are sometimes considered a double object, a double dwarf planet or a binary system.

In Roman mythology, Pluto (Greek: Hades) is the god of the underworld. In Greek mythology, Charon is the ferryman of Hades who carries souls of the newly deceased across the rivers Styx and Acheron that divided the world of the living from the world of the dead. Styx -river that formed the boundary between Earth and the Underworld. Nix - Greek goddess of the night Kerberos – Greek name for Cerberus – three headed hellhound. Hydra - gigantic, nine-headed water-serpent killed by Hercules

New Horizons launched on Jan. 19, 2006 Pluto closest approach on July 14, It takes one-way radio transmission from Pluto to Earth in July 2015: 4 hours, 25 minutes.

Eris is the largest dwarf planet in the Solar System, exceeding Pluto’s mass by 28%. Eris is the object the precipitated the definition of the category "dwarf planets" and the demotion of Pluto. Eris (Latin Discordia) is the Greek goddess of strife and discord. Revolution (Year) : Earth Years Rotation (Day) : hours

Ceres is by far the largest of the asteroids, comprising more than a third of the total mass of the main asteroid belt. Ceres is also the smallest of the dwarf planets. Discovered in 1801 by Guiseppe Piazzi. Visited in 2015 by the NASA Dawn Mission. Rotation (Day) – 9.1 hours Revolution (Year) – 4.6 Earth Years

Discovered in 2005 by a team of astronomers at the Palomar Observatory in San Diego. One of the largest known objects in the outer solar system, just slightly smaller and dimmer than Pluto. Scientists think it is about two-thirds the size of the more well- known dwarf planet. It orbits beyond the range of Pluto, but closer to the sun than Eris. Makemake is named for the god of fertility in Rapanui mythology. The Rapanui live on Easter Island in the southeastern Pacific Ocean. Rotation (Day) – 22.5 hours Revolution (Year) – 310 Earth Years

Discovered in 2003 by a team of astronomers at the Palomar Observatory in San Diego. Haumea is the third closest dwarf planet from the Sun and is unique in its elongated shape making it the least spherical of the dwarf planets. Named for the Hawaiian goddess of childbirth and fertility. Its two moons were named for daughters of the goddess, Hi'iaka and Namaka. Rotation (Day) – 3.9 hours Revolution (Year) – 281 Earth Years

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