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11.2 – The Sun and its Planetary Systems. To be a planet, 3 criteria must be met: Must orbit one or more stars Must be large enough that its own gravity holds it in a spherical shape Must be the only body occupying the orbital path. THE PLANETS. - PowerPoint PPT Presentation
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11.2 – THE SUN AND ITS PLANETARY SYSTEMS
THE PLANETS To be a planet, 3 criteria must be
met: Must orbit one or more stars Must be large enough that its own gravity holds it in a spherical shape
Must be the only body occupying the orbital path
This distance between planets is SO large that we don’t measure in kilometres!
Astronomical Unit (AU): equal to the average distance between the Sun and Earth (about 150 million km) Earth = 1 AU from the Sun Jupiter = 5.27 AU from the Sun
1. MOONS Also known as “satellites” All planets except Mercury and
Venus have 1 or more orbiting companions
Earth’s satellite is named the Moon More than 150 moons have
recognized in our solar system
2. ASTEROIDS Small bodies believed to be
leftover remains from the formation of the solar system
Most orbit the Sun in a band between Mars and Jupiter
Can be as small as grains of sand or up to 1000km wide (ex. Ceres)
3. COMETS Composed of ice, rock, and gas Originate from the Kuiper Belt and
the Oort Cloud Can get bumped into the inner
solar system Can see a trail of gas/dust when effected by sunlight
4. TRANS-NEPTUNIAN OBJECTS Objects that circle the Sun beyond Neptune’s
orbit Kuiper Belt
A flat disk of millions of small bodies orbiting the Sun
Believed to be made of fragments of material left over from the solar system’s formation
Dwarfs planets, similar in composition/size to Pluto, orbit in this belt Believed to be 23 objects in the Kuiper Belt
that may be considered planets
5. OORT CLOUD A spherical cloud of small icy
fragments Located at the farthest reaches of
the Sun’s gravitational influence Believed to be a source of comets Roughly 50,000-100,000 AU from
the Sun