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Formation of the Solar System
• The stages of solar system formation start with a protostar embedded in a gas cloud, then to an early star with a circumstellar disk, to a star surrounded by small "planetesimals" that are starting to clump together to a solar system like ours today.
Formation of the Solar System
www.jwst.nasa.gov/birth.html Credit: Shu et al. 1987
protostar circumstellar disk
planetesimals home
Structure(from the inside out)
• Central star
• Inner “terrestrial” planets
• Asteroid belt
• Outer “gas giant” planets
• Outer “ice giant” planets
• (Dwarf planets)
• Trans-Neptunian objects (Kuiper belt, scattered disk, Oort Cloud)
• Miscellaneous
The Sun
• “Yellow dwarf”, 1.4 million km in diameter
• Fuses 620 million tonnes/sec of H
• 8.3 light-minutes away
Mercury
• Innermost planet, 4,880 km in diameter
• Very dense, with its own magnetic field
• Enigmatically large iron core
• Recent evidence for volcanism
Venus
• Regarded as Earth’s “Evil Twin”
• Surface T: 460°C, P: 92 Bar
• Subject to runaway greenhouse effect
• Extensive resurfacing due to volcanism
Mars
• Diameter: ~6800 km (= Earth’s core)
• Same surface area of all Earth’s continents
• Deserts, ice caps, canyons, giant volcanoes
• Upper hemisphere may be giant impact basin
Asteroid Belt
• Small bodies: asteroids/minor planets
• >50% mass: Ceres, Vesta, Pallas, Hygiea
• Protoplanets that orbited too fast to acrete
• Mainly loosely-bound piles of rubble
Jupiter
• Largest body after the Sun (D: ~143,000 km)
• Primarily H, He, with putative rocky core
• High-energy storms in its atmosphere
• At least 63 moons
Saturn
• Second-largest planet, diameter ~121,000 km
• Prominent set of rings
• 53 officially-named moons
• Hosts largest moon in the system, Titan
Uranus
• Larger of the two “ice giants”, D ~51,000 km
• Gas atmosphere + contains H20, NH3, CH4
• Axis of rotation inclined almost 90
Neptune
• Second “ice giant”, D ~49,000 km
• Same composition as Uranus (H20, NH3, CH4)
• Tenuous ring system, 13 known moons
Dwarf Planets
• Currently 5: Ceres, Pluto, Haumea, Makemake, Eris
• Most occur beyond Neptune (except Ceres)
• Best known is Pluto (former planet)