Where are we? http://zebu.uoregon.edu/~js/ast122/
The Milky Way We are here Top view Side view • ~200 billion stars. • One revolution every ~200 million years.
Comparison of different stars Stars come in a wide range of sizes
And different emission temperatures… • Typical star b.b. temperatures range from 3000K to 20,000K. • Some stars look bluer, some look redder.
The Sun uv image
Some details about the sun: Gravitational collapse - high pressure, temperature Thermonuclear reaction: 4H+ He + 2e+ + 2n + 26.5MeV (1eV = 1.6 x 10-19J)
Sun Facts I: • Diameter: 1.4 million km • Age: 4.5 billion years (lifetime 11 billion years) • Mass: 2 x 1030 kg (330,000 x Earths) • (99.8% of mass of solar system) • Density: 1.41 (water = 1) • Composition (by mass): Hydrogen: 73%, Helium: 25%, • Others: 2%
Sun facts II: • Distance from Earth: 149.6 million km. • Distance to nearest Star: 9.46 million million km. • Luminosity: 4 x 1026 J s-1 (390 billion billion Megawatts). • Solar Cycle: 8 - 11 years. • Temperature at Surface: 5,800°C (10,500 °F). • Temperature of Core: 14 million°C (22.5 million °F) • Pressure at core: 250 billion atmospheres (2.5 x 1016 Pa) • Every second 700 million tons of hydrogen converted to • 695 million tons helium, and 5 million tons of energy.
Sunspots and coronal loops: jets of plasma trapped by sun’s magnetic field NASA (uv image from TRACE)
We are very small! (NASA, TRACE)
Sunspots II Royal Swedish Academy of Sciences Vacuum telescope
Structure of the Solar System Solar system formed from cloud of gas/debris from supernova Oort cloud - extends out 50,000 AU (1000 x Pluto’s orbit) (nearly a light year, 25% of distance to nearest star) Voyager 1: 125AU, edge of heliosphere, 17km/s, 36 years, = 17 light-hours from Earth
Structure of the Solar System Kuiper belt - Neptune to ~55AU > 70,000 objects with radius >1 km, including dwarf planets > 35,000 Kuiper Belt objects greater than 100 km Largely composed of frozen ices (volatiles - methane, water, amonia)
Structure of the Solar System Dwarf planet (plutoid): 1) is in orbit around the Sun. 2) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (near-spherical) shape. 3) has not cleared the neighborhood around its orbit. 4) is not a satellite.
Pluto (demoted 2006): Radius: 1137 km Mass: 1.3x1022 km Orbit: 5.9x109 km Made of: rock, ice Moons: 5 Atmosphere: ~tenuous CO2, CH4 Eliot Young (SwRI) et al., NASA
Neptune: • Radius: 24,766 km • Mass: 1.0x1026 kg • Orbit: 4.5 x 109 km • Made of: • ices (H20, CH4, NH3), • rock, hydrogen (15%) • helium • Atmosphere: yes • Moons: 13 known • Internal heat source • radiates twice the • energy it receives • Fastest winds in solar • system > 2000km/hr • 1 day = 16 hours • 1 year = 60,225 days (http://seds.lpl.arizona.edu/nineplanets)
Uranus: Radius: 25,559 km Mass: 8.7x1025 kg Orbit: 2.9 x 109 km Made of: ices, rock, hydrogen, helium Atmosphere: yes Moons: 27 n.b. axis of rotation parallel to plane of orbit! Day: 17 hours Year: 30,700 days 1 season = 1 year. (http://seds.lpl.arizona.edu/nineplanets)
Saturn: Radius: 60,268 km Mass: 5.7x1026 kg Orbit: 1.4 x 109 km Made of: hydrogen, helium ice, and rock Atmosphere: yes Moons: 62 Least dense planet 0.7 g cm-3 (water = 1) NASA, Hubble 10832 days Below molecular hydrogen and helium layer, a layer of metallic hydrogen: - a liquid soup of ionized protons and electrons. - occurs for pressures > 4 x 109 Pa (http://seds.lpl.arizona.edu/nineplanets) 1 year = 10832 days 1 day = 11 hours
Titan: Saturn’s largest moon Radius: 2576km Atmos. Pressure ~1.5 bar Temp ~-200oC Only known body (other than Earth) to have stable lakes Huygens Visible image (on its way down) Huygens Visible (landed) Hydrocarbon lakes on Titan (Cassini, radar)
Jupiter: Radius: 71,492 km Mass: 1.9x1027 kg Orbit: 7.8 x 108 km Made of: hydrogen (90%), helium (10%), ice, and rock Atmosphere: yes Moons: 61 Day: 9.8 hours Year: 4,333 days Io Europa (http://seds.lpl.arizona.edu/nineplanets)
An interior view http://www.alienalley.com/andrew1.html
The Asteroid belt Region where Jupiter’s gravity prevented formation of planets Made of rock and ice. Largest object: Ceres (~950 km radius) Frequent asteroid collisions a major Earth hazard…
Mars: Radius: 3,397 km Mass: 6.4x1023 kg Orbit: 2.3 x 108 km Made of: rock Atmosphere: yes (CO2) Moons: 2 1 year = 78 days 1 day = 25 hours Valles Marineris NASA & (http://seds.lpl.arizona.edu/nineplanets)
Mars contd:- machines on Mars... Curiosity Planetary Geology
Victoria crater (true color), seen by Martian rover (opportunity)
Martian landscapes dunes Gullies in a crater Dust devils over dunes Pockmarks in dry ice at the poles
It’s a tough neighbourhood out there…. Phobos, moon of Mars
Earth: Radius: 6,678 km Mass: 5.9x1024 kg Orbit: 1.5 x 108 km Made of: rock Atmosphere: yes (nitrogen, oxygen, argon) Moons: 1 Specific density 5.52 Densest planet in solar system 1 day = 25 hours 1 year = 365.25 days (http://seds.lpl.arizona.edu/nineplanets)
Venus: Radius: 6,052 km Mass: 4.9 x 1024 kg Orbit: 1.1 x 108 km Made of: rock Atmosphere: yes (CO2) Moons: No Surface pressure: 90 atm Surface temperature: ~750K 1 year = 225 days 1 day = 243 days! Surface Visible from space Venera 10 (http://seds.lpl.arizona.edu/nineplanets)
Mercury: Radius: 2,440 km Mass: 3.3x1023 kg Orbit: 5.8 x 107 km Made of: rock Atmosphere: yes (unstable) Moons: No Temperatures vary from 90K to 700K - largest range in solar system 1 year = 88 days 1 day = 59 days! (http://seds.lpl.arizona.edu/nineplanets)