more at http://scitech.quickfound.net/astro/planet_news.html
On the qualifications for labeling a heavenly body as a “planet.” “This question has been pondered by many since the early Greeks came up with the word “planetes”. Since then the number of “planets” in our solar system has fluctuated, sometimes numbering as high as 15, before it was determined that some were actually asteroids. Topic: A fascinating travel along the “Kuiper Belt highway” at 100mph to explore the far reaches of our solar system that discovers how vast our corner of the galaxy really is.”
Public domain film from NASA, slightly cropped to remove uneven edges, with the aspect ratio corrected, and mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).
The discovery of Eris led the International Astronomical Union to change their official definition of a planet, and deem Eris and Pluto “dwarf planets,” leaving the Solar System with 8 planets instead of 9.
At the 26th IAU General Assembly in August, 2006, the IAU resolved:
(1) A 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, 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,
(c) has not cleared the neighbourhood around its orbit, and
(d) is not a satellite.
(3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as “Small Solar System Bodies”.
1 The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
2 An IAU process will be established to assign borderline objects to the dwarf planet or to another category.
3 These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs),comets, and other small bodies.
The IAU further resolves:
Pluto is a “dwarf planet” by the above definition and is recognized as the prototype of a new category of Trans-Neptunian Objects.
An IAU process will be established to select a name for this category…
A planet (from Ancient Greek ἀστὴρ πλανήτης (astēr planētēs), meaning “wandering star”) is an astronomical object orbiting a star or stellar remnant that
– is massive enough to be rounded by its own gravity,
– is not massive enough to cause thermonuclear fusion, and
– has cleared its neighbouring region of planetesimals.
The term planet is ancient, with ties to history, science, mythology, and religion. Several planets in the Solar System can be seen with the naked eye. These were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, incorporating a number of disparate objects. In 2006, the International Astronomical Union (IAU) officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of planetary mass based on where or what they orbit. Although eight of the planetary bodies discovered before 1950 remain “planets” under the modern definition, some celestial bodies, such as Ceres, Pallas, Juno, Vesta (each an object in the Solar asteroid belt), and Pluto (the first trans-Neptunian object discovered), that were once considered planets by the scientific community are no longer viewed as such…
cool nasa videos- Pluto, et al: “What is a Planet?” 2007 NASA; IAU Definition of a Planet #Space #videos #NASA #News
Originally posted 2015-03-08 13:17:14. Republished by Blog Post Promoter