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!