AST309_Midterm1_Review_v4

AST309_Midterm1_Review_v4 - Midterm Review (v.4) There will...

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Midterm Review (v.4) s There will be 21 questions: 15 short answer like our quizzes and 6 requiring longer responses. s Know the following formulas: o Kepler’s 3 rd Law: P 2 = a 3 where P is the orbital period and a is the semimajor axis; o Enclosed Mass: M encl = (RV rot 2 ) / G o Schwarzchild Radius: R = 3km (M BH / B Sol ) (so a Black Hole with 10x the Sun’s Mass will have a radius of 30 km) s Not all of the questions will come from the following study guide, so we need to review these questions + lecture info + notes on website including Gamma Ray Bursts #1 … IOW, everything. Also, just because a question is asked about one aspect, e.g., #13, doesn’t mean he might not ask about one of the others instead. s Note that some of the below is from my own studies (e.g., AST 301) or conjecture. I have marked these by putting them in italics – you can choose to use them or not. s Notes in Arial are courtesy of Jeff Becker and Katie Lane – thanks! 1. Overview the details of Jupiter beginning to migrate inwards, including possible causes and effects. Describe the final state of our Solar System in this case. If, as we believe may have happened in some exosolar systems, Jupiter were to migrate inwards, it could be due to a number of possible causes: gravitational interaction with other stars, gravitational interaction with other planets, and gravitational drag. Gravita- tional Drag is exacted on an inward migrating planet due to interaction with the disc of material such as gas and dust surrounding it and slowing it down as it passes through this disc, creating a wake behind the planet. There is no 2 nd body involved here. The planet is not dragging another along. The planet is being slowed down by the gas and dust because there is so much of it. The question then is what becomes of Jupiter in this scenario. Possible results are: a. It keeps going until it falls into the sun, or b. It stops somewhere in a closer orbit. Several mechanisms for the latter have been suggested, including (1) Running out of disk with which to interact, possibly due to solar wind activity; (2) Magnetic fields from the disk interacting with and braking the planet’s sun- ward fall until it goes into close orbit; (3) Tidal locking with the sun acting to park the planet in close orbit.
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Whether Jupiter kept falling in or slowed into near orbit, it would have huge effect upon other planets on the way, clearing out other planets including our own as it goes, either: a. Flinging them to larger orbits or even out of the solar system altogether. b. Colliding with them; c. Tearing them apart with its gravitational field; d. Capturing them and turning them into satellites; 2. What is the difference between proper motion and radial velocity of a star? Proper motion
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This note was uploaded on 05/01/2008 for the course AST 309 taught by Professor Johnlacy during the Spring '08 term at University of Texas at Austin.

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AST309_Midterm1_Review_v4 - Midterm Review (v.4) There will...

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