UK DINOSAURS
AND DINOSAURS OF THE WORLD

New View of Solar System to Include Ceres, Pluto, Charon and 2003UB313 as Planets


British Dinosaurs

Acanthopholis
Altispinax
Anoplosaurus
Baryonyx
Becklespinax
Bothriospondylus
Camelotia
Camptosaurus
Cetiosauriscus
Cetiosaurus
Dacentrurus
Echinodon
Eotyrannus
Eustreptospondylus
Hylaeosaurus
Hypsilophodon
Iguanadon
Lexovisaurus
Macrurosaurus
Megalosaurus
Metriacanthosaurus
Neovenator
Polacanthus
Proceratosaurus
Regnosaurus
Sarcolestes
Sarcosaurus
Scelidosaurus
Thecodontosaurus
Valdosaurus
Yaverlandia

Not listed due to
doubtful evidence:


Aristosuchus
Calamospondylus
Callovosaurus
Chondrosteosaurus
Craterosaurus
Cryptosaurus
Iliosuchus

Nuthetes
Priodontognathus
Saltopus

Thecospondylus
 

The 'New' and Reduced Solar System from August 2006
Our Solar System consists of eight planets only

 
 

Pluto Moon Ceres ScaleIn August 2006, the International Astronomical Union (IAU) met to try to decide, once and for all, what Pluto was, and whether it deserved to be a planet. In doing so it became important to decide what constituted a planet.

What's the Problem with Pluto?

Pluto was discovered in 1930 although its existance was predicted mathematically due to gravitational forces which were being exerted at the edge of the solar system. However Pluto's discovery did not necessarily account for the predictions and its status has often been in doubt for various reasons. Then recent discovery of Eris in 2003 (formerly classified as '2003 UB313') caused a problem because this new 'planet' was of similar composition to Pluto but was larger than our existing 'ninth planet'. So if Pluto was a planet, surely Eris would be too. The discoveries of more bodies, such as 2005FY9 increased the problem. Why weren't these new bodies planets?

All the accepted eight planets are divided into either rocky worlds or gas giants. Pluto, being ice and rock, does not quite fit either group and is in some ways more like a comet. Pluto also lacked a normal-shaped circular orbit around the sun, having instead one which was very eliptical, more like Eris. Pluto was smaller than Mercury, Earth's moon and a variety of other satellites. Beyond the simple fact that people had got used to calling Pluto a planet, there was very little to support it's case for planetary status.


The Media Jumping the Gun

The week before a decision was made there was great media interest around the IAU meeting and prior to the final outcome, a propsal was publicised in which virtually any object with a spherical shape could have been upgraded to planetary status. A provisional number of 12 planets, increasing to 50 or more was on the horizon! This generated interest in the possible promotion back to planetary status of Ceres, the largest asteroid, which was happily thought of as a planet from its discovery in 1801 until it was reappraised 150 years later. A category of planet called 'Plutons' was also proposed which would have included any trans-Neptunian object of any decent size, including the afforementioned Eris. Ultimately these proposals were all rejected but their high-profile media coverage and the inaccurate television information (such as Channel 5 and Channel 4 News which even managed to mis-pronounce 'Charon') led to confusion.

Pluto is not a Planet

On August 24th 2006, the real definition of a planet emerged for the first time ever. It bore close resemblance to the initial proposal, but with one addition:

A planet is something around a star that can form itself into a solid sphere under the influence of its own gravity and it has cleared the neighbourhood around its orbit.

What this means is that any object which is merely the largest amongst a cloud of other objects will not count, such as Ceres, the largest asteroid of the astoid belt.

A second definition was made, which is that any object which is nearly round due to its own gravity but has not cleared its orbit (and is not a satellite of another object) is a Dwarf Planet.

Pluto has been placed in this second category of Dwarf Planet and is no longer one of "The Planets". As such there are only eight planets in our solar system. Eris also belongs in this category.

The diagram below is the best illustration of why Pluto does not belong in the family of planets. When its orbit is plotted alongside its fellow trans-Neptunian objects, it blends into this crop of icy oddballs quite happily and bears little relation to its more weighty and uniform cousins.



Pluto, Eris, Sedna, Xena, Quaoar trans-neptunian objects

Above: A graphic showing the eight main eight planets and their circular orbits, versus the eccentric orbits of the trans-Neptunian "Dwarf Planets" which now include Pluto, Eris, Quaoar, Sedna, et al.


Gavin Rymill 2006