更新1: 呢套纪录片中文名系(篮地球)
系讲海洋生物架~!
A pla
as defined by the International Astronomical Union (IAU)
is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity
not massive enough to cause thermonuclear fusion
and has cleared its neighbouring region of plaesimals.[1][2] The term pla is an ancient one having ties to history
science
myth
and religion. The plas were originally seen as a divine presence; as emissaries of the gods. Even today
many people continue to believe the movement of the plas affects their lives
although such a causation is rejected by the scientific munity. As scientific knowledge advanced
the human perception of the plas changed over time
incorporating a number of disparate objects. Even now there is no uncontested definition of what a pla is. In 2006
the IAU officially adopted a resolution defining plas within the Solar System. This definition has been both praised and criticized
and remains disputed by some scientists. The plas were initially thought to orbit the Earth in circular motions; after the development of the telescope
the plas were determined to orbit the Sun
and their orbits were found to be elliptical. As observational tools improved
astronomers saw that
like Earth
the plas rotated around tilted axes and shared such features as ice-caps and seasons. Since the dawn of the Space Age
close observation by probes has found that Earth and the other plas share characteristics such as volcani ***
hurricanes
tectonics and even hydrology. Since 1992
through the discovery of hundreds of extrasolar plas (plas around other stars)
scientists are beginning to observe similar features throughout the Milky Way Galaxy. Under IAU definitions
there are eight plas in the Solar System (Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
and Neptune) and 270 extrasolar ones.[3] The Solar System also contains at least three dwarf plas (Ceres
Pluto
and Eris). Many of these plas are orbited by one or more moons
which can be larger than *** all plas. Plas are generally divided into o main types: large
low-density gas giants and *** aller
rocky terrestrials.