Friday, May 1, 2009
Pluto..
Pluto is no longer considered to be the planet. It is t be called the dwarf planet henceforth. Delegates of the 26th General assembly if the international astronomical union took this stunning decision on august 24, 2006 in the Czech capital prague. Pluto was discovered in 1930 by an U.S astronomer clyde jombaugh and name dafter the roman God of the underworld. Pluto has an icy surface composed of nitrogen and methane and weighs just the fifth of the weight of our moon. According to the new IAU definition a planet is a celestial body that is in orbit around the sun; has sufficient mass of its self gravity to overcome the rigid body forces so that it assumes a nearly round shape and has cleared the neighbourhood around its orbit. Pluto does not pass the last requirement because the its orbit crosses into Neptunes.
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This highly controversial decision is only one side of an ongoing debate. Only four percent of the International Astronomical Union voted on this, in a process that violated their own bylaws, and most are not planetary scientists. Their decision was immediately rejected by hundreds of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA's New Horizons mission to Pluto. Stern and like-minded scientists favor a broader planet definition that includes any non-self-luminous spheroidal body orbiting a star. The spherical part is important because it means an object is large enough for its own gravity to pull it into a round shape--a characteristic of planets and not of shapeless asteroids. This debate could be resolved by simply amending the IAU resolution to make dwarf planets a subclass of planets that are planets because they are spherical but are of the dwarf subcategory because they do not gravitationally dominate their orbits. In the meantime, it is perfectly reasonable to use the broader planet definition, under which our solar system has 13 planets and counting: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Haumea, Makemake, and Eris.
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