Phys 101

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https://openstax.org/details/books/astronomy .


 Show your work!  Don’t forget units ON ALL NUMBERS!   Use scientific notation and round your answers to 1 or 2 digits. Draw a diagram if you find it helpful to explain something.   Staple all pages together.  Remove any fringe from the paper edge. 

 

1. Scaling Problem: For this problem, consult the tables in Appendix E & F of the textbook for conversions, sizes, and distances.  Careful with your units. a) If Earth were the size of a tennis ball (6.5 cm diameter), what would the size of the Sun be (in meters)?  What is something approximately that large? b) If Earth were the size of a tennis ball, how far away would the sun be in this scaled down system?  What is something approximately that far away? c) If the diameter of Earth’s orbit around the Sun were the size of a tennis ball, how far away would the nearest star (distance, d = 4.2 ly) be [in km (and miles if those are easier for you to visualize)]?  What is something approximately that far away? 

 

2. Cosmic Insignificance Problem: A typical galaxy contains 100 billion stars and there are about 100 billion galaxies in the observable Universe. a) Compute the number of stars in the observable Universe.  About 5% of these stars are like our own Sun – how many Sun-like stars are out there? b) If only a tiny fraction (0.01%) of Sun-like stars host terrestrial planets like Earth, how many Earth-like planets are out there? c) Given your answer to (b), comment on the possibility of life elsewhere in the Universe. 

 

3. Relative Distances Problem: Would the constellations we know appear the same if you were transported to: a) another planet in the Solar System? b) a planet around Proxima Centauri, the sun’s nearest stellar neighbor (d=4.2 ly)? c) a planet around a star 5000 ly from the sun? 

 

Explain your answers. 

 

4. Celestial Sphere Problem: Alpha Centauri, the closest star to the sun, has R.A. and Dec. (, )= (14h 40m, -60 50’).   Is Alpha Centauri ever visible from Ellensburg?  Explain your reasoning. Name a place on Earth or list a range of latitudes from which Alpha Centauri is circumpolar (never goes below the horizon). 


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