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.
Getting closer…
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)
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
NASA, Hubble
10832 days
(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
Hydrocarbon lakes on
Titan (Cassini, radar)
Huygens
Visible image
(on its way down)
Huygens
Visible
(landed)
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
Europa
Io
(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
Valles
Marineris
1 year = 78 days
1 day = 25 hours
NASA & (http://seds.lpl.arizona.edu/nineplanets)
Biggest bump in the solar system: Olympus Mons, 24km high!
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
Visible from space
Surface
Surface temperature:
~750K
Venera 10
1 year = 225 days
1 day = 243 days!
(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)