Chapter 8Components: The SunComponents: The PlanetsPlanets with Distance to ScaleWhat about Pluto?Asteroids and CometsAsteroids and CometsOrbits and Spins of the PlanetsOrbits and Spins of the PlanetsBode’s RuleSlide 11Slide 12Slide 13Composition of the PlanetsComposition of the PlanetsFormation of Solar SystemsFormation of the Solar SystemSlide 18Interstellar CloudsHow did a cloud become a disk?Formation of Solar NebulaCondensation in the Solar NebulaCondensationSlide 24Formation of the PlanetsFrom what raw materials do planetary systems form?Why are Jupiter and the other gas giants so big?Jupiter’s Giant GravityFormation of Satellite SystemsFormation of Atmospheres and Cleaning Up the MessExoplanetsExoplanets: Method 2 - Doppler ShiftDoppler Shift MethodExoplanets: Method 3 - Gravitational LensingExoplanets: Method 4 - TransitsSlide 36Slide 37Known Systems with at least 4 ExoplanetsChapter 8Survey of Solar SystemsComponents: The Sun•The Sun: Heart of our Solar System.•Ball of burning gas sustained by nuclear fusion.•Contains most of the mass of the Solar System (700 times the mass of all other bodies put together)•The gravity of the Sun is what holds all the planets in their orbits. (Rule #1)•Composed mainly of Hydrogen (71%) and Helium (27%), with trace amounts of nearly all other elements.Components: The Planets•Eight planets: Terrestrial: Mercury, Venus, Earth, Mars Jovian: Jupiter, Saturn, Uranus, Neptune•Nearly circular orbits. •Emit no visible light, simply reflect it.•Jovian planets have deep hydrogen-rich atmospheres.•Jupiter is 10 times the radius of Earth, and 318 times the mass. (still less dense than Earth)Planets with Distance to ScaleWhat about Pluto?•Pluto doesn’t seem to fit either category nicely. •It’s orbit is more eccentric and tilted from the ecliptic more than other planets.•After discovering half a dozen objects similar in size, it was either 14+ planets or 8 planets.•New rules for what makes a planet. 1) In orbit around the sun 2) Sufficient mass to pull itself into a spherical shape 3) Has “cleared the neighborhood” around its orbit•New designation called “dwarf planets” for Pluto (and friends)•Even dwarf planets can have moons. Pluto has 4.Asteroids and Comets•Asteroids: Rocky/metallic bodies orbiting the sun that are far smaller than planets.•Most asteroids are found in the “asteroid belt” between Mars and Jupiter.•Ceres: Largest body in the asteroid belt. •Has a spherical shape, contains 25% the entire mass of the asteroid belt.•Ceres is a dwarf planet, just like Pluto.Asteroids and Comets•Kuiper Belt: Similar to asteroid belt, but made mostly of ice.•Many dwarf planets orbit in the Kuiper belt, including Pluto. •Kuiper belt is past the orbit of Neptune, around 50 AU from the sun.•Some objects come from even FURTHER out, giving clues to what’s out there. Comets.•Comets have highly elongated orbits and many spend most of their time in the Oort Cloud. (may extend to 100,000 AU)Orbits and Spins of the PlanetsSaturnJupiterVenusMercury•The planets lie in a straight line across the sky, the ecliptic.•No planet’s orbit is tilted by more than 7º from the ecliptic.•All planets orbit the Sun the same direction, counter clockwise (when viewed from above the North pole)Orbits and Spins of the Planets•Rotation of the planets is (generally) in same direction as orbit of planets. Moons follow this same pattern for their orbits around their parent planet.•Venus spins backward relative to other planets. Uranus is tilted sideways, perhaps due to some catastrophic impact.•Dwarf planets often have highly inclined orbits with large axial tilts.•Kuiper belt objects have inclined orbits up to about 45º but average out to the same plane as the ecliptic. •Comets can come from ANY direction.•Conclusion: Kuiper belt is a disc, Oort cloud is a sphere.Bode’s Rule•Not a Law or a Theory.•No scientific basis for these ideas, but simulations often produce similar results.•Orbits stable over billions of years generally have factors of 1.5 to 2 between the orbital size of neighboring planets.How many terrestrial planets are there? How many jovian planets?A. 3, 5B. 4, 4C. 4, 5D. 5, 4E. 5, 3Which of the following is true regarding the orbits and rotations of the planets?A. All planets orbit the same direction, and most rotate the same directionB. All planets rotate the same direction, and most orbit the same directionC. All planets orbit and rotate the same directionD. Most planets orbit and rotate the same directionWhich planets are the exceptions to consistent direction of rotation of other planets?A. Earth and VenusB. Venus and MarsC. Mars and UranusD. Venus and UranusE. Mercury and MarsComposition of the Planets•Can look at the spectrum produced by the planet, but this only tells us about atmosphere or surface rocks.•Density of the planet tells us about what’s on the inside. (Find mass using orbital motion of a moon, find radius using angular size + known distance)•Comparing densities has its issues: 1. Multiple “correct” answers 2. Densities change based on pressures involvedComposition of the PlanetsDensity3.9 - 5.5 g/ccDensity0.7 - 1.7 g/ccFormation of Solar Systems•All planets orbit in the same plane.•Most planets rotate in the same direction as they orbit.•Outer planets: Very similar composition to the Sun.Inner planets: Same composition as outer planets, minus compounds with low vaporization temperatures.•All bodies in the Solar system seem to have formed around the same time, around 4.6 billion years ago, with the smaller bodies cooling first.•The Sun has a similar age as well (based on rates of fuel consumption)•Any theory of how the Solar System formed must explain these observations.Formation of the Solar System•Current favored theory: Solar Nebula Theory•Proposed in 1700s by a German philosopher and a French mathematician.•The solar system formed from a rotating flattened disk of dust and gas.•The center of the disk became the sun, and the outer parts became the planets.•Nothing about this process is unique to our Solar System, so we can look for other systems forming to follow the same steps.How do the compositions of the Jovian planets compare to the Terrestrial planets?A. The compositions are nearly identicalB. The compositions are similar, but the Jovian planets lack materials with high vaporization