Pluto “demoted”
This is the latest news which shocked the astronomical world when it was announced on 24 August 2006. International Astronomical Union (IAU) declared on Thursday onwards that there are only eight (8) planets which orbit around the sun; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. So, what happened to Pluto? After seven decades as the ninth and outermost planet, it’s now “demoted” to a category known as dwarf planets, which comprises of 2003 UB313 (Xena which was themed the ‘tenth’ planet) and large asteriod Ceres. Pluto was discovered on February 18 1930 by a 24-year-old American astronomer, Clyde Tombaugh.
IAU’s ruling will rewrite schoolbooks and reshape notions about space topography. All the while throughout the years, we were taught that Pluto is a unique planet; taking more than 200 years to complete its orbit and orbiting at a tilted angle as compared to the other 8 planets. Well, I think their decision to scrap the title was a hard one. But, by doing so, it will stop the inclusion of larger than Pluto objects found in the Kuiper Belts as planets. As telescopes get better, we will be seeing further. It would be better than having to modify textbooks every year like the tenth, eleventh, twelveth, etc.. planets.
A sidetrack, Pluto now has three moons: Charon, discovered in 1978, and the tiny Nix and Hydra, spotted in 2005 by US astronomers using the orbiting Hubble Space Telescope. Charon is about half the size of Pluto, you can see the quite bright ’star’ in the picture. Nix and Hydra can be spotted as tiny stars at the right side of the photo. However, even though the ruling has changed, it does not matter to Pluto or me. Pluto will still continue to orbit the sun as it always does. I’ll always remember Pluto as the unique planet.
Following extract is obtained from Physorg.com
When is a planet not a planet?
Following is the text approved by the International Astronomical Union (IAU) at an assembly in Prague on Thursday that defines a planet and other Solar System objects.
The resolution reduces the number of acknowledged planets from nine to eight, downgrading Pluto to the new status of “dwarf planet.”
“Contemporary observations are changing our understanding of planetary systems, and it is important that our nomenclature for objects reflect our current understanding.
“This applies, in particular, to the designation ‘planets’. The word ‘planet’ originally described ‘wanderers’ that were known only as moving lights in the sky. Recent discoveries lead us to create a new definition, which we can make using currently available scientific information.
“The IAU therefore resolves that ‘planets’ and other bodies in our Solar System be defined into three distinct categories in the following way:
“(1) A ‘planet’ (1) is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
“(2) A ‘dwarf planet’ is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape (2), (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
“(3) All other objects (3) except satellites orbiting the Sun shall be referred to collectively as ‘Small Solar-System Bodies’. (…)
“Pluto is a ‘dwarf planet’ by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.
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