Post on 26-Dec-2015
Where are we?
http://zebu.uoregon.edu/~js/ast122/
We are here
• ~200 billion stars.• One revolution every ~200 million years.
Side view
Top view
The Milky Way
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
> 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
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 kmMass: 1.3x1022 kmOrbit: 5.9x109 kmMade of: rock, ice Moons: 5Atmosphere: ~tenuous
CO2, CH4
Eliot Young (SwRI) et al., NASA
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)
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.
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
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)
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)
http://www.alienalley.com/andrew1.html
An interior view
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…
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
Biggest bump in the solar system: Olympus Mons, 24km high!
Mars contd:- machines on Mars...
Planetary Geology
Curiosity
Victoria crater (true color), seen by Martian rover (opportunity)
Martian landscapes
dunes
Gullies in a crater
Dust devils over dunes
Pockmarksin dry ice at the poles
It’s a tough neighbourhood out there….
Phobos, moonof Mars
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
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)
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!