Pity Poor Pluto: It’s Been Demoted (August 28, 2006)
View of Pluto (lower left) and its moon Charon from the Hubble Space Telescope. The planet was 2.6 billion miles (4.6 billion kilometers) away when the picture was take, nearly 30 times Earth’s distance from the Sun. NASA/European Space Agency.
Suddenly, every solar system poster hanging in every classroom around the world is out of date. After years of lively debate, astronomers announced some stunning news: Pluto is not a planet any more.
The International Astronomical Union’s (IAU) decision changes the list of planets for the first time since Pluto was discovered in 1930. From now on, poor Pluto will be considered a dwarf planet.
The change in Pluto’s status follows from the IAU’s new definition of a planet. To be a planet, a solar system body must be massive enough for its gravity to pull it into the shape of a ball. Secondly, the body must orbit the Sun. It also cannot share its “neighborhood” in space with any other bodies…. more…
