Where are we?
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Transcript of Where are we?
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Where are we?
http://zebu.uoregon.edu/~js/ast122/
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We are here
• ~200 billion stars.• One revolution every ~200 million years.
Side view
Top view
The Milky Way
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Comparison of different stars
Stars come in a wide range of sizes
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And different emission temperatures…
• Typical star b.b. temperatures range from 3000K to 20,000K.
• Some stars look bluer, some look redder.
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Getting closer…
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The Sun
uv image
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Some details about the sun:
Gravitational collapse - high pressure, temperature
Thermonuclear reaction: 4H+ He + 2e+ + 2n + 26.5MeV
(1eV = 1.6 x 10-19J)
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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%
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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.
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Sunspots and coronal loops:jets of plasma trapped by sun’s magnetic field
NASA (uv image from TRACE)
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We are very small!
(NASA, TRACE)
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Sunspots II
Royal Swedish Academy of Sciences Vacuum telescope
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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
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Structure of the Solar System
> 70,000 objects with radius >1 km, including dwarf planets> 35,000 Kuiper Belt objects greater than 100 kmLargely composed of frozen ices (volatiles - methane, water, amonia)
Kuiper belt - Neptune to ~55AU
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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.
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Pluto (demoted 2006):
Radius: 1137 kmMass: 1.3x1022 kmOrbit: 5.9x109 kmMade of: rock, ice Moons: 5Atmosphere: ~tenuous
CO2, CH4
Eliot Young (SwRI) et al., NASA
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Neptune:
Radius: 24,766 kmMass: 1.0x1026 kgOrbit: 4.5 x 109 kmMade of: ices (H20, CH4, NH3), rock, hydrogen (15%) heliumAtmosphere: yes Moons: 13 known
-Internal heat source radiates twice the energy it receives
-Fastest winds in solarsystem > 2000km/hr
1 day = 16 hours1 year = 60,225 days
(http://seds.lpl.arizona.edu/nineplanets)
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Uranus:
Radius: 25,559 kmMass: 8.7x1025 kgOrbit: 2.9 x 109 kmMade of: ices, rock,
hydrogen, heliumAtmosphere: yes Moons: 27
n.b. axis of rotation parallel to plane of orbit!
(http://seds.lpl.arizona.edu/nineplanets)
Day: 17 hoursYear: 30,700 days
1 season = 1 year.
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Saturn:
Radius: 60,268 kmMass: 5.7x1026 kgOrbit: 1.4 x 109 kmMade of: hydrogen, helium
ice, and rockAtmosphere: yes Moons: 62
Least dense planet
0.7 g cm-3 (water = 1)
NASA, Hubble
(http://seds.lpl.arizona.edu/nineplanets)
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
10832 days
1 year = 10832 days1 day = 11 hours
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Titan: Saturn’s largest moon
Hydrocarbon lakes onTitan (Cassini, radar)
Radius: 2576kmAtmos. Pressure ~1.5 barTemp ~-200oC
Only known body (other than Earth) to have stable lakes
HuygensVisible image(on its way down)
HuygensVisible(landed)
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Jupiter:
Radius: 71,492 kmMass: 1.9x1027 kgOrbit: 7.8 x 108 kmMade of: hydrogen (90%),
helium (10%), ice, and rock
Atmosphere: yes Moons: 61
Day: 9.8 hoursYear: 4,333 days
Europa Io(http://seds.lpl.arizona.edu/nineplanets)
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http://www.alienalley.com/andrew1.html
An interior view
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The Asteroid belt
Region where Jupiter’s gravity prevented formation of planetsMade of rock and ice.Largest object: Ceres (~950 km radius)
Frequent asteroid collisions a major Earth hazard…
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Mars:
Radius: 3,397 kmMass: 6.4x1023 kgOrbit: 2.3 x 108 kmMade of: rockAtmosphere: yes (CO2)Moons: 2
1 year = 78 days1 day = 25 hours
NASA & (http://seds.lpl.arizona.edu/nineplanets)
VallesMarineris
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Biggest bump in the solar system: Olympus Mons, 24km high!
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Mars contd:- machines on Mars...
Planetary Geology
Curiosity
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Victoria crater (true color), seen by Martian rover (opportunity)
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Martian landscapes (not true color)
dunes
Gullies in a crater
Dust devils over dunes
Pockmarksin dry ice at the poles
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It’s a tough neighbourhood out there….
Phobos, moonof Mars
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Earth:
Radius: 6,678 kmMass: 5.9x1024 kgOrbit: 1.5 x 108 kmMade of: rockAtmosphere: yes (nitrogen, oxygen, argon)Moons: 1
Specific density 5.52
(http://seds.lpl.arizona.edu/nineplanets)
Densest planet insolar system
1 day = 25 hours1 year = 365.25 days
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Venus:
Radius: 6,052 kmMass: 4.9 x 1024 kgOrbit: 1.1 x 108 kmMade of: rockAtmosphere: yes (CO2)Moons: No
Surface pressure:90 atm
Surface temperature:~750K
1 year = 225 days1 day = 243 days!
Visible from space Surface
Venera 10
(http://seds.lpl.arizona.edu/nineplanets)
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Mercury:
Radius: 2,440 kmMass: 3.3x1023 kgOrbit: 5.8 x 107 kmMade of: rockAtmosphere: yes (unstable)Moons: No
Temperatures vary from 90K to 700K - largest range in solar system
(http://seds.lpl.arizona.edu/nineplanets)
1 year = 88 days1 day = 59 days!