Lec19-Mar31

Lec19-Mar31 - 3/31/10 Discussion Ques4on The major...

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Unformatted text preview: 3/31/10 Discussion Ques4on The major planets lie in a plane and orbit the Sun in the same direc4on. This is strong evidence that Astro 109 Lecture 19: Forma4on of the Solar System March 31 A.  the solar system resulted from the collision of two medium ­sized stars. B.  the planets formed elsewhere in the Galaxy and were then captured by the Sun. C.  the solar system formed from a rota4ng cloud of gas that collapsed to form the Sun and planets. D.  aMer the planets formed, collisions between them eventually caused them all to move in the same direc4on. E.  None of the above. We do not have any idea how our solar system may have formed. Mar. 31 Key Concepts •  Solar nebula, protoplanetary disk •  Building planets: planetesimals, accre4on •  Evidence for a violent past Mar. 31 Mar. 31 Discussion Ques4on What physical process caused the solar nebula to form a disk as it collapsed? A.  B.  C.  D.  E.  Mar. 31 conserva4on of energy conserva4on of eccentricity conserva4on of angular momentum nuclear fusion Kepler’s first law Mar. 31 1 3/31/10 Seeing protoplanetary disks Mar. 31 Mar. 31 Mar. 31 Mar. 31 Mar. 31 Mar. 31 2 3/31/10 Discussion Ques4on Discussion Ques4on Which statement best describes the origin of the terrestrial planets? Which statement best describes the origin of the Jovian planets? A.  Ini4ally gentle collisions between par4cles of ice and dust led to the build ­up of massive cores which then captured a lot of hydrogen and helium. B.  Rocky dust par4cles combined to form planetesimals that later merged into a few large objects. C.  Hydrogen and helium collapsed to form large objects that later captured a lot of ice. D.  There were four solid objects in the gas cloud before it started to collapse. E.  They are debris leM over from the forma4on of the inner planets. A.  Ini4ally gentle collisions between par4cles of ice and dust led to the build ­up of massive cores which then captured a lot of hydrogen and helium. B.  Rocky dust par4cles combined to form planetesimals that later merged into a few large objects. C.  Hydrogen and helium collapsed to form large objects that later captured a lot of ice. D.  There were four solid objects in the gas cloud before it started to collapse. E.  They are debris leM over from the forma4on of the inner planets. Mar. 31 Mar. 31 Discussion Ques4on Asteroids Is there any debris leM over from the coagula4on process that created the planets? A.  No, all the material was used up in forming the planets. B.  No, all leMover material was burned up in the Sun. C.  No, all leMover material was ejected from the solar system by Jupiter and Saturn. D.  Yes, but we cannot see it because it is too small. E.  Yes, there is debris leM over in the form of asteroids and comets. Mar. 31 Mar. 31 Discussion Ques4on Most craters on the Moon were formed by Evidence for a violent past Mar. 31 A.  B.  C.  D.  E.  impacts from falling objects. volcanic erup4ons. con4nental driM. geysers. nuclear explosions. Mar. 31 3 3/31/10 Mimas Cratering Moon Mercury Mars Mar. 31 Mar. 31 Mar. 31 Mar. 31 Age of Earth’s surface Discussion Ques4on When we see that part of the surface of a planet (or moon) is less heavily cratered than other regions, we conclude that A.  there is liale volcanic ac4vity to create craters. B.  this part of the surface was protected from impacts by the planet’s slow rota4on. C.  the en4re planet must have formed aMer the age of bombardment. D.  this part of the surface is older than the rest. E.  this part of the surface is younger than the rest. Mar. 31 •  Earth is geologically ac4ve  ­ ­> few features are truly old •  Evidence for a hot past! Mar. 31 4 3/31/10 Mar. 31 Mar. 31 Chemical differen4a4on Mar. 31 Mar. 31 July 1994 Forma4on of the Moon Comet Shoemaker ­Levy 9 Impacts s4ll happen Mar. 31 Mar. 31 5 3/31/10 Mar. 31 Mar. 31 HW ques4ons Chapter 7 17. How does the size of a terrestrial planet influence the amount of cratering on the planet’s surface? 33. The surfaces of Mercury, the Moon, and Mars are riddled with craters formed by the impact of space debris. Many of these craters are billions of years old. By contrast, there are only a few conspicuous craters on the Earth’s surface, and these are generally less than 500 million years old. What do you suppose explains the difference? Chapter 8 11. What are proplyds? What do they tell us about the plausibility of our model of the solar system’s origin? Mar. 31 Mar. 31 HW ques4ons 13. What is a planetesimal? How did planetesimals give rise to the terrestrial planets? 19.  Explain how our current understanding of the forma4on of the solar system can account for the following characteris4cs of the solar system: (a) All planetary orbits lie in nearly the same plane. (b) All planetary orbits are nearly circular. (c) The planets orbit the Sun is the same direc4on in which the Sun itself rotates. 32. Suppose you were to use the Hubble Space Telescope to monitor one of the protoplanetary disks shown in Figure 8 ­8b. Over the course of 10 years, would you expect to see planets forming within the disk? Why or why not? Mar. 31 6 ...
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