Homeworks 1
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Homeworks 1 is the attempted solution to our second task[1] in the course Introduction to Astrophysics. This assignment is due on Wednesday 09/09/09 and was assigned on 09/01/09.
Problem 1
List in order of increasing size and give the approximate size of the following objects: An atom, a biological cell, a cluster of galaxies, the Earth, a galaxy, the Local Group of galaxies, a neutron, a neutron star, a person, the Solar System, our sun. Note: you may have to look in other books besides your textbook to get all this information.
Problem 2
The nearest star outside the solar system is about 4 light years away.
- How far away is the star in kilometers?
- Suppose you travel to the nearest star in a rocket ship moving at 100 km per hour (100 km/hr is
about 62 mi/hr, a typical automobile speed on a Florida highway). How many years will it take you to get to the star?
- Suppose you travel to the star at 10 km per second (the speed of a rocket in orbit around the Earth). How many years will it take you to get to the star?
Problem 3
Use the size of the Astronomical Unit in kilometers and the length of the year in seconds to calculate how fast the Earth moves in its orbit in kilometers/second.
Problem 4
Describe the essential differences between the Ptolemaic, Copernican, and Keplerian descriptions of planetary motion.
Problem 5
Use Newton’s laws to show that the orbits of planets are ellipses.
Notes
References
- B.W. Carroll & D. A. Ostlie (2007). An Introduction to Modern Astrophysics. Addison Wesley. ISBN 0-8053-0402-9