Chapter 1 The Water Planet

1. Chapter 1The Water Planet

2. Origin of the Universe Earth, a small, rocky planet, orbits the . . . the sun, a medium sized star, . . one of billions of stars in the Milky Way galaxy, . . one of billions of galaxies in the universe.

3. Origin of the Universe Brightness of pulsating stars – cepheid variables – was used to determine distance from Earth Brighter stars = closer to Earth Dimmer stars = farther from Earth Repeated measurements determined cepheid variables were moving away from Earth Interpretation  the universe is expanding Size of the Universe: Luminosity

4. Origin of the Universe Size of the Universe: Doppler Effect Doppler Effect:The apparent change in the frequency of sound waves or light waves due to the motion of a source relative to an observer • Example: change in frequency (pitch) of a siren from passing police car

5. Origin of the Universe Doppler Effect Example: The change in frequency (pitch) of a siren from passing police car No change in frequency for sound waves when police siren and observer are stationary Higher frequency when sound waves are compressed for objects moving toward an observer Lower frequency when sound waves are stretched out for objects moving away from an observer

6. Origin of the Universe Light on Earth is a form of solar radiation and occurs at specific wavelengths from 380-750 nanometers Size of the Universe: Doppler Effect • The color of light from distant stars is stretched (“shifted”) toward wavelengths at the red end of the spectrum Shorter wavelength Longer wavelength

7. Origin of the Universe Size of the Universe: Doppler Effect • Astronomers use the degree of “red shift” to determine the distance to far away galaxies • more than 13 billion light years (distance) from Earth

8. Origin of the Universe The Big Bang Theory • Reversing the expansion of the universe suggests the universe began with an episode of rapid expansion from a much more compact form • The almost instantaneous period of rapid expansion is known as the Big Bang • Within hours of the Big Bang, simple elements (hydrogen, helium) formed as subatomic particles combined • Hydrogen – 1 proton + 1 electron • Helium – 2 protons + 2 neutrons + 2 electrons

9. Stars and Planets • Just 3 elements – hydrogen, oxygen, carbon - make up 90% of the human body (by weight) • Five more – nitrogen, calcium, phosphorus, potassium, sulfur – make up 9% more • Small amounts of many other elements needed for life • Hydrogen formed soon after the Big Bang • Other elements and complex compounds formed during the life cycle of stars

10. Stars and Planets • Gravity pulled together irregular clouds of gas and dust generated from the Big Bang to form galaxies (systems of stars) Stars and galaxies in a small section of the universe. Image taken by Hubble space telescope

11. Stars and Planets • Gas and dust material clumped together to form millions of stars (ongoing process) • Very high temperatures and pressures in the interiors of stars fuses hydrogen atoms together – nuclear fusion – to form helium • Some stars burn out when hydrogen is used up. Others can fuse elements up to iron (Fe) False color image from NASA Spitzer Space telescope showing cool gas and dust that are incubators for new stars.

12. Stars and Planets • Giant stars collapse over multiple stages, initially forming red supergiant stars • Collapse forms increasingly complex elements (e.g., carbon  oxygen) • Final stage is a massive explosion – supernova – that fuses elements together forming elements heavier than iron and blasts them through the universe Kepler’s supernova. Astronomer Kepler noted the appearance of a new star (the supernova) on October 9, 1604.

13. Stars and Planets • When stars form they are surrounded by a rotating disk of cosmic debris • Gravity pulls debris together to form planets that revolve in a consistent direction around star • Heavier, rocky planets closer to star • Lighter, gas-rich planets farther from star • Potentially thousands or millions of extra-solar planets revolve around other stars

14. Our Solar System • Solar system - sun and surrounding planets • Sun = 99.8% of total mass of the solar system • Sun 150,000,000 km from Earth Sunspots – dark spots on surface of sun Solar flare

15. Our Solar System • The solar wind is a stream of charged particles emitted from sun’s magnetic field (1,600,000 km/hr) • The solar wind affects an volume of space known as the heliosphere • Earth’s magnetic field deflects the solar wind

16. Our Solar System • Interactions of solar wind with Earth’s magnetic field generates aurora in the upper atmosphere of polar regions • Occasional solar eruptions can disrupt Earth’s magnetic field to produce electrical blackouts • Satellites in greater danger from solar flares than features on surface Aurora from Earth Aurora from space

17. Our Solar System • Eight Planets • 4 terrestrial planets (Mercury, Venus, Earth, Mars) • Jovian planets (Jupiter, Saturn, Uranus, Neptune)

18. Our Solar System • What about Pluto? • Improved technology resulted in recent discoveries of several distant objects that were similar size or larger than Pluto • International Astronomical Union (IAU) could either • Consider the new objects as new planets • OR • Classify the new objects – and Pluto – as a new group of objects • IAU chose option #2

19. Pluto • What about Pluto? • IAU adopted a new definition of the term planet: • A planet is an object that orbits a star and is massive enough (~400 km radius) for gravity to pull its material into an approximately spherical shape. A planet would have cleared the neighborhood around its orbit. • Pluto does not meet the last part of the definition and was considered a founding member of a new class of objects - dwarf planets

20. Our Solar System • Terrestrial Planets • Composed of rocks • Divided into compositional layers • Crust – composed of lighter elements (e.g., silicon, oxygen) • Mantle • Core – composed of heavier elements (e.g., iron, nickel) found in metallic meteorites The Good Earth, Chapter 2: Earth in Space

21. Our Solar System • Jovian Planets • Large, gas giants • Much of the volume of the planets is a thick atmosphere overlying oceans of liquid gases • Characterized by many moons and ring systems Jupiter and four of its largest moons. Saturn’s ring system. The gravitational pull of the moon’s keep the ring systems in place.

22. The Unique Composition of Earth Earth shares many features with other planets, so what makes it so special? • Liquid water • Gravity and a protective atmosphere • Life-sustaining gases • A strong magnetic field

23. The Unique Composition of Earth Earth’s size is sufficient to produce enough gravity to hold a thick atmosphere of gases in place • Atmosphere protects us from: • Incoming small asteroids/comets • Harmful solar radiation (x-rays, UV)

24. The Unique Composition of Earth Earth’s biosphere has altered the composition of the atmosphere to add oxygen and extract toxic carbon dioxide • Atmosphere composition effects temperature: • Higher carbon dioxide content on Venus produces temperatures of 464oC

25. The Unique Composition of Earth Composition of Earth’s atmosphere just right to absorb enough heat to keep average temperature of 15oC • Greenhouse effect: • Water vapor, carbon dioxide (0.038%) gases absorb heat • Without greenhouse effect, temperatures would be -18oC

26. The Unique Composition of Earth Earth’s magnetic field protects Earth from harmful solar wind that would strip away atmosphere Magnetic field due to molten rocks in the outer core and relatively rapid planetary rotation: • Smaller planets or slowly rotating planets have lost heat and have weak magnetic fields

27. Earth’s Moon Four theories for Moon formation: Fission: Rapid spin spun moon from Pacific Ocean. Improbable. Capture: Moon formed elsewhere in solar system but was gravitationally captured. Improbable. Condensation: Moon condensed close to earth in solar nebula formation. Improbable. Giant Impactor: Mars-sized body (Theia) impacted Earth 50 million years after initial formation. Best accounts for Earth-Moon characteristics.

28. Earth’s Moon