The solar system and a lot of science-y words Astronomy 115, Spring 2013.

The solar system and a lot of science-y words

Astronomy 115, Spring 2013

Comparing the Sun and Earth

Comparing the Sun and Earth

size:

1) The radius of the Earth is r = 6371 km

2) The radius of the Sun is R = 7x105 km

R

Comparing the Sun and Earth

mass:

1) The mass of the Sun is m = 2 x 1030 kg

2) The mass of the Earth is m = 6 x 1024 kg

3) The ratio of Sun to Earth masses = 3.3 x 105

If the Sun weighed as much as the aircraft carrier Independence………

The Earth would only weigh as much as two members of its crew….

What is the densest round object in the solar system?

1. Jupiter2. Earth3. Sun4. Venus

Comparing the Sun and Earth

density:

1) The density of the Sun is d = 1.4 g cm-3

2) The density of the Earth is d = 5.5 g cm-3

1 paper clip weighs about 1 gram (g)

1 cubic centimeter (cm-3) is about the size of a sugar cube

Water has a density of 1 g cm-3 while lead is 10.8 g cm-3

Comparing the Sun and EarthComposition:

Earth (rocks)

34.6% iron

29.5% oxygen

15.2% silicon

12.7% magnesium

2.4% nickel

1.9% sulfur

Earth (air)

78% nitrogen

21% oxygen

0-4% water

1% argon

0.035% carbon dioxide

0.0017% methaneSun

92.1% hydrogen

7.8% helium

0.1% carbon or oxygen

0.001% iron

Comparing the Composition of the Earth and Planets:

Earth

34.6% iron

29.5% oxygen

15.2% silicon

12.7% magnesium

2.4% nickel

1.9% sulfur

Jupiter

92.1% hydrogen

7.8% helium

0.1% carbon &

oxygen

0.001% iron

Neptune

(Atmosphere)

83% hydrogen

15% helium

2% methane

(Interior)

?? water ice

?? silicon

?? iron

?? oxygen

Jupiter is almost exactly like the Sun, while the Earth, and to a lesser degree, Neptune are different.

Comparing the Sun and Earth

Time and Evolution:

The Earth

102 -104 s lightning, storms

104 -105 s tides, diurnal cycle

107 s seasons

1011 - 1012 s ice ages, climate changes

1015 - 1016 s plate tectonics, magnetic polarity reversals, evolution

1017 s age of Earth (4.5 billion years)

The most significant changes to surface conditions on the Earth were brought about by loss of some atmospheric gases and the

emergence of life.

Changes in the Earth’s atmosphere

Time and Evolution:The Early Earth

atmosphere similar to solar composition

100x thicker than today

hydrogen-helium

4.5-3.5 billion years (by) ago

The Young Earth

hydrogen/helium lost

oceans form/ CO2 from volcanic activity

CO2 dissolved in oceans

3.5 – 0.5 by

The Living Earth (0.5 by to Present)

nitrogen dominates as CO2 is lost/modern atmospheric density

plants evolve (photosynthesis begins) - oxygen concentration increases - feedback with sun’s evolution.

animals adapt to O2 metabolism - move to land

O2 in atmosphere: life’s smoking gun/impossible without

Comparing the Sun and Earth

Time and Evolution:

The Sun

104 s Convection at visible surface

105 - 106 s Flares – solar events – Oscillations

2x106 s Solar rotation

107 - 108 s Magnetic cycle

1015 - 1016 s Energy transport – Changes in core

1017 s Age of Sun (4.5 billion years)

2x1017 s Sun becomes a red giant/stellar death

Temperature Scales

K = 273 + (°F - 32)/1.8

Comparing the Sun and Earth

Temperature:

SunSurface 5000 – 10000 K (visible)

Atmosphere 2 million K (Corona)

Core 15 million K

EarthSurface 300 K (average ground)

Atmosphere 300 – 1000 K (ground to top)

Interior 3000 – 7700 K

K = 273 + (°F - 32)/1.8

273 K = 32°F, 373 K=212° F, and 273 K = 0°C

Put the following regions of the Sun in order from hottest to coldest

1. Core, atmosphere, surface2. Core, surface, atmosphere3. Surface, atmosphere, core4. Surface, core, atmosphere5. Atmosphere, core, surface6. Atmosphere, surface, core

Energy Production from the Sun:

The Sun dominates the energy ‘budget’ of the solar system

• How much energy does the Sun produce?• How does the energy reach us?

• How does it produce that energy?

Energy• Types of energy

– Kinetic energy (energy of motion)– Thermal energy (energy of heat)– Electromagnetic energy– Gravitational energy– Chemical energy– Nuclear energy

• For big energies: joule (J)• For small energies: electron-volt (eV)

[Note: 1 eV = 1.6x10-19 J]

Energy and Power

• Power is energy per time, orwatt (W) = joules (J) /seconds (s)

• Power Companies use kilowatt-hours as unit of energy or 1000 x (J/s) x hr

1 kWh = 3.6 x 106 J

How much energy do we use?

A typical power bill in the Seattle area will be for about 1200 kilowatt hours (kWh) in one month, or about 400 kWH per person.

The USA as a whole uses

400 kWh x 12 month x 3.0 x 108 people = 1.44 x 1012 kW h

How does that compare with the Sun?