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The Sun and the Origin of the Solar System. Mid-sized, G-type main sequence star Distance: 1 AU = 150 million km away Size: Actual radius 700,000 km = 100 Earths Temperature, Luminosity (surface) T = 6000 K http://www.nasa.gov/multimedia/videogallery/index.html.
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Mid-sized, G-type main sequence star • Distance: 1 AU = 150 million km away • Size: Actual radius 700,000 km = 100 Earths • Temperature, Luminosity (surface) T = 6000 K http://www.nasa.gov/multimedia/videogallery/index.html
99.86% of the total mass of the Solar System • 75% hydrogen, 23% heliun • 2% O, C, Ne, Fe
Sunspots • surface areas that are darker than surroundings (lower temperatures) • regions of intense magnetic activity
Stellar Evolution • The Sun is a middle-aged, low-mass, main-sequence star • 5 billion years ago: • Beginning of its life on main-sequence • Sun had 1/3 luminosity it has now. • 5 billion years from now: • End of its life on main-sequence • Sun will have twice the luminosity it has now.
When H is exhausted, core shrinks. • Heats up • High temperatures ignites a shell of H around the core. • Increased pressure drives the envelope of the star outward. • Creates a Red giant
Contraction of core, raises the temperature • Ignites He shell around the core • Eventually the core stabilizes • Envelope is ejected as a "planetary nebula" • The core remains as a "white dwarf"
Solar system formation • Starting point: • A cloud of interstellar gas and dust, the "solar nebula“ • Most of it (98%) is hydrogen and helium, includes dust grains of heavier material, formed in previous generations of stars.
Contraction • Accretion disk • Protostar • Condensation • Planetesimals
Asteroid Belt • Small bodies in the inner solar system • Asteroid Belt between Mars & Jupiter. • Orbits are strongly influenced by Jupiter. • Made of rock, metal, or a mix of the two.
>300,000 asteroidal objects • >150,000 with good enough orbits to give official numbers • ~15,000 asteroids with official manes • When you know its orbit, you can name it.
Examples of asteroid names • Ceres (largest – 914 km) • Eros (landed on in2001 Feb 12) • Bach • Beethoven • Lennon • McCartney • Santana • Clapton
Irregular shape • Too small for gravity to make them spherical
Composition of Asteroids • C-type: "Carbonaceous" – mostly carbon-bearing materials. ~75% of all asteroids. • S-type: "Silicaceous" - mostly of silicates (stony or stony iron). 17% of all asteroids. • M-type: "Metallic" - probably iron-rich
Asteroid Origins • fragments of larger, differentiated bodies shattered by collisions • remnants of more primordial material that never got differentiated
Impact with Earth Would disrupt climates and trigger mass extinctions
Meteoroids • Chunks of rock & iron smaller than asteroids orbiting the Sun • Sizes range from grains to 100 meters across
Meteor • Streak of light when a meteoroid enters the Earth's atmosphere • Most are tiny grains • Meteor showers are trails of debris left behind by passing comets
Meteorite • Any remnant that reaches the ground intact.
Russian Meteorite • http://www.youtube.com/watch?v=90Omh7_I8vI
Meteor Impacts • About 100 tons of meteoroids hit the Earth each day • Most are no bigger than grains of sand or smaller
Earth Impact Effects Program http://impact.ese.ic.ac.uk/ImpactEffects/
Comets Small bodies consisting of aggregates of ices mixed with rock & dust
As they approach the Sun, they heat up and the ices sublimate (go from solid to gas):
Halley's Comet • In 1705, Edmund Halley computed the orbit of the great comet of 1682 using Newton's laws • Found that orbit of 1682 comet was the same as comets seen in 1531 & 1607. • Predicted return in 1758. • Seen again on Christmas day 1758, 12 years after Halley's death
Origin of Comets • Short-period comets are from the Kuiper Belt • Long-period comets are from the Oort Cloud
Structure of Comets • Nucleus: • Dirty snowball of ices & dust • >99% the mass of the comet • Coma • Bright "head" of the comet • Low-density cloud of gas & dust sublimed off the nucleus • Extends out to 100,000 km or more
Comets have two tails • Dust Tail, dusty particles swept back in a curved path by solar radiation, white • Ion Tail, ionized atoms & molecules swept straight back by the solar wind, blue
Comet Orbits • Typically have a high degree of eccentricity http://www.windows2universe.org/comets/comet_model_interactive.html
Kuiper Belt • Region of the Solar System beyond the planets extending from the orbit of Neptune (at 30 AU) to approximately 55 AU from the Sun
Oort Cloud • Cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. • Nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun