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1. Review for Midterm II Please press “1” to test your transmitter. • 1 • 2 • 3 • 4 • 5 :10 0 of 5

2. The pre-birth phase of a star is called … • Baby star • Pre-star • Starillo • Protostar • supernova :10 0 of 5

3. 0 Protostars Protostars = pre-birth state of stars: Hydrogen to Helium fusion not yet ignited Still enshrouded in opaque “cocoons” of dust => barely visible in the optical, but bright in the infrared.

4. Dense pockets gas in a giant molecular cloud which ultimately form stars, are called … • Starlets • Globules • Open star clusters • Star pockets • protostars :10 0 of 5

5. 0 (Bok) Globules Compact, dense pockets of gas which may contract to form stars. ~ 10 – 1000 solar masses; Contracting to form protostars

6. From Mercury to Neptune, the average density of the planets … • Steadily decreases • Steadily increases • Remains almost constant. • Increases throughout the terrestrial planets, then decreases. • Decreases throughout the terrestrial planets, then increases. :10 0 of 5

7. 0 Condensation in the Early Solar System The Condensation Sequence Only condensed materials could stick together to form planets Temperature in the protostellar cloud decreases outward. Lighter substances condense at lower temperatures. Further out → Protostellar cloud is cooler → lighter metals with lower melting point condensed → change of chemical composition throughout solar system → Average density of planets decreases outwards!

8. Planets orbiting stars other than our sun are scientifically called … • Alien Worlds • Extragalactic planets • Extra-universalplanets • Extrasolar planets • Jovianplanets :10 0 of 5

9. 0 Extrasolar Planets All stars have gone through basically the same formation process as the sun. → Many stars should have planets! → planets orbiting around other stars = “Extrasolar planets” Extrasolar are very hard to image directly. Detection using the “wobbling” technique: Look for “wobbling” motion of the star due to the gravitational pull of the planet on the star.

10. How did the Jovian planets grow? • Only by random encounters with rocky clumps in the protoplanetary cloud. • First by random encounters with rocky clumps, then by gravitational attraction. • First by gravitational attraction of gas and dust, then by random encounters with rock and gas clumps. :10 0 of 5

11. The Story of Planet Building Planets formed from the same protostellar material as the sun. Rocky planet material formed from clumping together of dust grains in the protostellar cloud. Mass of more than ~ 15 Earth masses: Mass of less than ~ 15 Earth masses: Planets can grow by gravitationally attracting material from the protostellar cloud Planets can not grow by gravitational collapse Earthlike planets Jovian planets (gas giants)

12. What is differentiation? • Centrifugal forces flinging heavy metals out to the outer layers of a planet, while lighter materials remain near the core. • The sun’s gravity pulling heavier metals towards it, while lighter ones remain at the opposite side. • Heavier metals sinking to the cores of planets, while the lighter ones remain in the crust. :10 0 of 5

13. 0 The Growth of Protoplanets As rocks melted, heavier elements sink to the center → differentiation → Terrestrial planets have heavy-metal (iron) cores and mantles of lighter substances

14. Near the Earth’s center, we find … • A core of solid iron. • A core of liquid iron. • A core of liquid silicon-based rocks. • A core of solid silicon-based rocks. • A core of pure gold. :10 0 of 5

15. 0 Earth’s Interior (II) Basic structure: Solid crust (light [Si-based] materials) Solid mantle (light elements, iron-poor) Liquid core (iron-rich) Solid inner core (iron-rich) Earth’s interior gets hotter towards the center. Earth’s core is as hot as the sun’s surface; metals are liquid near the core.

16. Earth’s Interior 0 Direct exploration of Earth’s interior (e.g. drilling) is impossible. Earth quakes produceseismic waves. Earth’s interior can be explored throughseismology: Seismic waves are bentor bounce off transitions between different materials or different densities or temperatures.

17. Earth quakes, tsunamis, and volcanic activity on Earth occur predominantly near … • large oceans. • the core of the Earth. • the centers of large continents. • the boundaries of tectonic plates. • the top of the atmosphere. :10 0 of 5

18. 0 Geological activity around the Pacific Earthquakes: Kobe (Japan) Volcanism: Mt. St. Helen Volcanism: Pinatubo (Philippines) Earthquakes: San Francisco

19. Volcanoes related to subduction zones are found … • Only on Earth. • Only on Mars. • Only on Venus. • Only on Mercury. • On all terrestrial planets. :10 0 of 5

20. Volcanism on Earth (II) 0 Shield Volcanoes Found above hot spots: Fluid magma chamber, from which lava erupts repeatedly through surface layers above. All volcanoes on Venus and Mars are shield volcanoes

21. The Alps have been formed by the collision between … • The North American and the South American Plate • The Pacific Plate and the Eurasian Plate • The Eurasian and the North American Plate • The Afrian and the Eurasian Plate • The Afrian and the Indian-Australian Plate. :10 0 of 5

22. 0 Earth’s Tectonic History

23. 0 History of Geological Activity Surface formations visible today have emerged only very recently compared to the age of Earth.

24. X-rays from space interact with the atmosphere primerily through … • The dissociation of ozone molecules. • Inducing rotations of air molecules in the troposphere. • Inducing vibrations of air molecules in the troposphere. • Ionizing atoms and molecules in the Exosphere and Thermosphere. • Not at all: X-rays traverse the atmosphere nearly unabsorbed. :10 0 of 5

25. 0 The Electromagnetic Spectrum Wavelength Frequency High flying air planes or satellites Need satellites to observe

26. 0 The Temperature Structure of Earth’s Atmosphere Exosphere: Heated by UV and X-rays from space Thermosphere: Heated by X-rays from space Stratosphere: Heated by UV radiation from space Top of Ozone Layer Ozone Layer Altitude Troposphere: Heated by greenhouse effect Temperature Atmosphere gets colder at larger distance from heat sources.

27. The most essential step in the greenhouse effect is … • The dissociation of ozone molecules by ultraviolet light. • The ionization of air molecules by X-rays. • The heating of air molecules by gamma-rays. • The absorption of infrared light by complex molecules in the stratosphere. • The absorption of optical light by complex molecules in the stratosphere. :10 0 of 5

28. The Interactions between Light and Molecules 0 Infrared Causes asymmetric molecules to rotate This is the essential step of the Greenhouse Effect! Carbon dioxide (CO2) / Water vapor (H2O) / any other asymmetric molecules (greenhouse gases)

29. Which of the following is a greenhouse gas? • Hydrogen (H2) • Oxygen (O2) • Nitrogen (N2) • Ammonia (NH3) • All of the above. :10 0 of 5

30. 0 Greenhouse Gases Gases consisting of compounds of two or more different types of atoms: • CO2 (carbon dioxide) • H2O (water vapor) • CH4 (methane) • NH3 (Ammonia) Most common gases in Earth’s atmosphere (N2, O2) do not contribute to the greenhouse effect.