Our Evolving Universe
Self Test 1

1. In discussing stars, parallax refers to
   1. the apparent motion of a star through the night, caused by the Earth's rotation
   2. the difficulty in seeing stellar colours with the naked eye, because of the eye's physiology
   3. the apparent motion of a star through the year, caused by the Earth's orbit
   4. the distortions in telescopic images of the stars, caused by imperfect telescope optics
   
   
2. Compared to the 30 or so nearest stars, the Sun is
   1. brighter than most
   2. fainter than most
   3. about average
   4. impossible to compare, because we have no way of knowing how bright these stars really are
   
   
3. Sirius has apparent magnitude -1.5 and absolute magnitude 1.4, while Rigel has apparent magnitude 0.1 and absolute magnitude -7. Therefore
   1. Sirius appears brighter but is really fainter (and closer)
   2. Sirius appears fainter but is really brighter (and further away)
   3. Sirius appears brighter and really is brighter
   4. Sirius appears fainter and really is fainter
   
   
4. The mass of a star can be measured
   1. only if its distance is known
   2. only if its size (radius) is known
   3. only indirectly, by estimating from other properties - there is no direct way to do it
   4. only if it has a suitable binary companion
   
   
5. The Earth's distance from the Sun (one astronomical unit) is about eight light minutes. The nearest stars are
   1. hundreds of astronomical units away
   2. thousands of astronomical units away
   3. hundreds of thousands of astronomical units away
   4. hundreds of millions of astronomical units away
   
   

out of 5.

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