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Lecture 6: The origin of the solar system. Terrestrial. vs. Jovian. planets. Heavy elements (Fe,Mg,Si..). Terrestrial:. Got rocks, volcanoes, craters. Can stand on surface. smaller. Closer to the Sun. hotter. H, He. Jovian:. Mainly gas…. Bigger. Outer part of solar system. colder.
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Terrestrial vs Jovian planets
Heavy elements (Fe,Mg,Si..) Terrestrial: Got rocks, volcanoes, craters Can stand on surface smaller Closer to the Sun hotter H, He Jovian: Mainly gas… Bigger Outer part of solar system colder Pluto is a bit of an exception
Composition? Go there and get samples…. Spectroscopy…
Gas (atmosphere) Titan (Saturn) molecules Europa (Jupiter) solid
Names of the planets in order from the centre? Mercury, Venus, Earth, Mars, Jupiter, Saturn,Uranus, Neptun, Pluto Where have we (humans)landed? Moon, Earth Where have we sent unmanned spacecrafts/probes to land? Moon, Venus, Mars, Jupiter,Titan Where have we sent spacecrafts to “fly by”? All except Pluto
“ice” for astronomers...
Asteroids Eros ~20Km Hints to formation of the solar system?
„Asteroid“ is Greek for star-like – denotes small, rocky objects in solar system The first asteroid was discovered in 1801: Ceres – 940 km in diameter There may be more than 1,000,000 asteroids > 1 km in diameter The main Asteroid belt lies between Mars and Jupiter
Where do comets come from? Hale-Bopp
Comets are small, irregular, icy and rocky objects that show a tail as they approach the Sun Comets fall into two main classes: - Short period comets (P<200 yr). Source: Kuiper belt - Long period comets (P>1000 yr). Source: Oort Cloud The main parts of a comet are the nucleus, coma, tail and extended hydrogen cloud Comets are essentially dirty snowballs composed of water and other ices, silicates and organic compounds Comet impacts may have brought substantial quantities of water and organics to the planets
Solar nebula Kelvin-Helmholtz contraction Conservation of angular momentum
Remember: ice= methane, ammonia, water, carbon dioxide
dust Chemical and electric forces then gravity Planetesimals (~1 km ) chondrules protoplanets World-shattering collisions planets Total >400 million years
simulation Terrestrial planets Jovian planets: outer regions and bigger!
How could an alien from a far away planet know that there’s life on Earth? On which planets you could stand on the surface?
Why some planets have atmosphere and others don’t? Why Venus, Earth and Mars do not have light H, He in atmosphere? v 2 “average” velocity of a gas particle The distribution is broad http://jersey.uoregon.edu/vlab/Balloon/ Look here for a demo:
Potential energy Calculate escape velocity….: example of a rocket: if kinetic energy is smaller than the potential energy, rocket can’t escape Earth gravity, if it is larger it can By setting Kinetic energy=potential energy you can compute the escape velocity Exercise….
Density and average density. 3 Surface rocks on earth: 3000 Kg/m 3 Average density: 5000 Kg/m Hints to formation history…
jets T-Tauri wind