It is now official. Scientists meeting in Prague have demoted the planet Pluto to the secondary status of dwarf planet. The decision was based on the fact that Pluto’s orbit overlaps with that of Neptune, which disagrees on the third required characteristic of being a planet. In fact, during the same meeting, scientists redefined a planet as a celestial body which
- is in orbit around the Sun
- is large enough that it takes on a nearly round shape
- has cleared its orbit of other objects
We understand the ambiguity when we consider the previous definition of a planet: a celestial body moving in an elliptical orbit round a star. (Oxford Dictionary). A quote from the BBC’s article on the subject explains the history behind the debate:
Pluto’s status has been contested for many years. It is further away and considerably smaller than the eight other “traditional” planets in our Solar System. At just 2,360km (1,467 miles) across, Pluto is smaller even than some moons in the Solar System.
But the real reason for Pluto’s demotion came with a discovery in 2003, which seemed to indicate that if Pluto was in fact a planet, then a number of other celestial bodies should be considered a planet, adding about 20 new planets to our Solar System.
The critical blow for Pluto came with the discovery three years ago of an object currently designated 2003 UB313. After being measured with the Hubble Space Telescope, it was shown to be some 3,000km (1,864 miles) in diameter: it is bigger than Pluto.
One thing is for sure, my kids are now going to have to learn new rhymes for the names of the eight planets of the Solar System: “My Very Expensive Mercedes Just Smashed Up a Nissan”. Or the less common “My Very Elderly Mother Just Sat Upon a Needle”. Gone are the days of ‘New Porches’ and ‘North Poles’. Too sad.
Information on Pluto (From the BBC’s article)
It was named after the god of the underworld in Roman mythology.
Orbits Sun every 248 years
Diameter of 2,360km
Has at least three moons
Rotates every 6.8 days
Gravity about 6% of Earth’s
Surface temperature -233C
Nasa probe visits in 2015
- A Newsvine Seed by Ekibitz: Pluto is Not a Planet Anymore
- A BBC News report on the subject: Pluto loses status as a planet