sun is the centre of our solar system

solar system full of planets, moons, asteroids, and comets

• all revolve around the sun at the centre

when a star forms from a nebula, gravity pulls most of the material into the new star, some may also clump together to form objects in a solar system

planet - celestial body that orbits one or more stars

each planet may also spin on its axis as it orbits the sun

planet requirements

• celestial body must orbit one or more stars, be large enough that its own gravity holds it in a spherical shape, and be the only body occupying the orbital path

order

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• sun, mercury, venus, earth, mars, jupiter, saturn, uranus, neptune

solar system formed 4.5+ billion years ago

after the sun formed, material closest to the sun developed into inner/terrestrial planets

• small, solid cores, rocky crusts

• mercury, venus, earth, mars

material further from the sun developed into the outer/Jovian planets

• large gaseous bands, cold temperatures

• jupiter, saturn, uranus, neptune

distance between planets in solar system measured in astronomical units (AU)

one AU = average distance from sun to earth

inner planets relatively close to centre of the solar system

• mars is 1.52 au from sun, vs jupiter is 5.27 au from the sun

• neptune is 30.06 au from sun

rotation

• motion of earth as it spins on its axis from west to east

• spins on axis at 1670km/hr (one full rotation takes almost a day)

revolution

• motion of earth as it orbits usn

• orbits sun at 30km/sec - one full revolution takes almost a year

sun

• contains more than 99% of mass in solar system

• composed of mainly hydrogen gas

• nuclear reactions in the sun’s core causes hydrogen to form helium

• energy is radiated to earth, keeping it warm enough to support life

solar wind

• sometimes gases from sun erupt outwards like bursting soap bubble

• resulting solar wind is full of high energy particles that would kill any life on earth they struck

• our magnetic field deflects this solar wind

  • see the deflection when we see the northern lights

asteroid - small leftover remains from the formation of the solar system

• thousands of asteroids orbit in the asteroid belt between mars and jupiter

comet - composed of ice, rock, and gas (dirty snowballs)

• leaves trail of gas and dust when in contact with sunlight

other solar system bodies

• bodies smaller than planets in our solar system

• moons found around all planets except mercury and venus

• asteroids found mainly between mars and jupiter in the asteroid belt

  • thought these are the leftovers from the formation of the solar system

• comets are rocky travelers - following orbits faroutside planets in the oort cloud

• oort cloud - at farthest reach of the sun’s gravitational pull, almost 25% of way to next nearest star, proxima centauri

trans-neptunian objects

• beyond neptune

• compoesd of fragments of material left over from formation of the solar system

• these objects orbit the sun in a larger area known as the kuiper belt

• pluto is a dwarf planet

why is pluto no longer a planet [video]

• pluto hasn’t been a planet since 2006

• demoted at the 26th general assembly of international astronomical union in prague (2006)

• only argument for keeping it was “tradition” - no scientific justification for calling pluto a planet

• it’s out in kuiper belt - asteroid belt past neptune - trillion things in belt

• nearly all are chunks of ice and rock like pluto, we just discovered pluto first

• pluto isn’t even biggest , eries - 25% bigger by mass than pluto

• haumea, makemake, ceres

• up to 100 big things in kuiper belt

• downgrade because so many big planets

• planet would stop being useful as a term

• new criteria : orbit sun, have enough gravity to pull itself into spherical shape, clear everything out of mass

  • only 0.07 times mass of everything in orbit vs earth is 1.7mil times

• dwarf planets follow only the first two criteria

• dwarf planets past neptune called plutoids

• new horizons spacecraft will go past pluto in 2015