29:50 Modern Astronomy
First Hour Exam
September 29, 2003
Form A

Read through the question and all the answers before choosing. Budget your time. There are 30 questions. No whining.

Walk with Ursus!

1. Which of the following is an indicator that the climate of Mars might have been much different in the remote past from what it is now?
   (a) The fact that the semimajor axis of the Martian orbit is now 1.88 au
   (b) The presence of dry water channels on the surface X
   (c) The fact that it possesses a very tenuous carbon dioxide atmosphere
   (d) The fact that the obliquity of the ecliptic for Mars is exactly 25.2 degrees
   (e) We have discovered extensive deposits of carbonate rocks on the surface, dating from the earliest days of the solar system.
2. If you go outside in the early evening now (8-9 PM), where will you find Mars?
   (a) In the south-to-southeastern sky X
   (b) Low in the western sky
   (c) Straight overhead, in the vicinity of the zenith
   (d) In the early evening, Mars has not yet risen
   (e) In the evening, Mars has already set
3. What is the approximate size (diameter) of Mars relative to the Earth?
   (a) About one-tenth
   (b) 3.5 times
   (c) About 10 times
   (d) About half X
   (e) About the same
4. The meridian is the astronomical term for
   (a) the line across the sky where the Sun and all the planets are to be found.
   (b) the point on the sky straight overhead.
   (c) an imaginary line on the sky that runs from due north, through the zenith to due south. X
   (d) an imaginary line on the sky from straight east, overhead to straight west.
   (e) the day of the year when day and night are of equal length.
5. Which of the following is a correct description of the location of Mars in the solar system?
   (a) It is the closest planet to the Sun.
   (b) It lies between the orbits of Venus and the Earth.
   (c) It is the next planet beyond the Earth. X
   (d) It lies at a distance of 10 astronomical units from the Sun.
   (e) It is the next planet beyond Saturn.
6. The average distance between the Sun and the Earth is defined as the
   (a) Kilometer
   (b) Parsec
   (c) Astronomical Unit X
   (d) Light Year
   (e) Solar Distance Unit
7. If you could travel between the inner planets at the speed of a fast car, how long would your trip typically take?
   (a) Many days
   (b) 4 to 5 months
   (c) Several thousand years
   (d) Several million years
   (e) Several years X
8. Planet X has an orbital period of 2 years, and orbits outside the orbit of the Earth. On September 1, we see Planet X at opposition. Which of the following is a correct description of the locations of the Sun, Earth, and Planet X?
   (a) The Earth, Sun, and Planet X make an angle of 45 degrees, with the Earth at one end, the Sun in the middle (the Apex), and Planet X on the other end.
   (b) They are on a straight line, with Planet X on one end, the Sun in the middle, and the Earth on the other end.
   (c) They are on a right angle with the Earth at one end, the Sun in the middle (the apex), and Planet X on the other end.
   (d) The Earth, Sun, and Planet X make an angle of 27.5 degrees, with the Sun at one end, the Earth in the middle (the Apex), and Planet X on the other end.
   (e) They are on a straight line with the Sun on one end, then the Earth, then Planet X. X
9. Consider Planet X again, this time on December 1. Which of the following is a correct description of the locations of the Sun, Earth, and Planet X in December?
   (a) The Earth, Sun, and Planet X make an angle of 45 degrees, with the Earth at one end, the Sun in the middle (the Apex), and Planet X on the other end. X
   (b) They are on a straight line, with Planet X on one end, the Sun in the middle, and the Earth on the other end.
   (c) They are on a right angle with the Earth at one end, the Sun in the middle (the apex), and Planet X on the other end.
   (d) The Earth, Sun, and Planet X make an angle of 27.5 degrees, with the Sun at one end, the Earth in the middle (the Apex), and Planet X on the other end.
   (e) They are on a straight line with the Sun on one end, then the Earth, then Planet X.
10. The reason for great current scientific and popular interest in Mars is
    (a) it appears the most likely object in the solar system to harbor life. X
    (b) definite evidence for the presence of life has been found.
    (c) Mars at one time had an advanced civilization of intelligent creatures.
    (d) Mars is the only other terrestrial planet in the solar system.
    (e) it is the only object other than the Earth in the solar system to possess a magnetic field.
11. Distances to stars are determined by a measurement of
    (a) color index.
    (b) stellar spectra.
    (c) stellar Class I distance indicators.
    (d) trigonometric parallax. X
    (e) absorption lines.
12. Consider the distances to the nearest stars, and how they compare with the distances between the planets. Roughly speaking, the nearest stars are how many times more distant than the planets?
    (a) 10 to 20 times more distant
    (b) several hundred thousand times more distant X
    (c) 1500 times more distant
    (d) millions of times more distant
    (e) $2.3 \times 10^{12} - 4.5 \times 10^{14}$ times more distant
13. In the horizon system of coordinates for describing the position of an object in the sky, the two coordinates are
    (a) Right Ascension and Declination
    (b) latitude and longitude
    (c) galactic latitude and longitude
    (d) altitude and range
    (e) altitude and azimuth X
14. In the Celestial Coordinate System (system fixed with respect to the stars) the two coordinates are
    (a) Right Ascension and Declination X
    (b) latitude and longitude
    (c) galactic latitude and longitude
    (d) altitude and range
    (e) altitude and azimuth
15. If you get up and go outside in the early morning, before sunrise, you can see the bright stars Betegeuse (red color, apparent magnitude = +0.41) and Capella (yellow color, apparent magnitude=+0.05). Based on this information alone, what can you say about these two stars?
    (a) Capella is hotter than Betelgeuse X
    (b) Betelgeuse is hotter than Capella
    (c) Betegeuse is more distant than Capella
    (d) Betelgeuse is more luminous than Capella
    (e) Capella is older than Betelgeuse
16. You look at two stars in the night sky and notice that one is brighter than the other. With this simple observation, you see that which of the following properties or characteristics are different for these two stars?
    (a) absolute magnitude
    (b) apparent magnitude X
    (c) surface temperature
    (d) distance
    (e) luminosity
17. A solid, opaque object can be heated to different temperatures. What happens to the light emitted by this object as the temperature increases?
    (a) The spectrum changes from a continuous spectrum to an emission line spectrum
    (b) The object becomes bluer, and stays at the same brightness.
    (c) The power radiated in infrared radiation increasingly dominates that emitted at ultraviolet wavelengths.
    (d) The object gets brighter and the light shifts to shorter wavelengths. X
    (e) The object gets brighter and the light shifts to longer wavelengths.
18. Light emitted by an incandescent light bulb and that from a low density, hot Helium gas look very similar to the human eye. How do the spectra compare?
    (a) The light bulb has an emission line spectrum, the helium a continuous spectrum.
    (b) Both light sources have emission line spectra, but the wavelengths are entirely different.
    (c) The light bulb has a continuous spectrum, the helium an emission line spectrum. X
    (d) The spectra are also very similar.
    (e) Both have continuous spectra, but the light bulb emits in the ultraviolet and the helium gas in the infrared.
19. Wien's Law expresses a relationship between
    (a) the temperature of a hot object and the degree of agitation of the atoms of which it is made.
    (b) the type of spectra emitted by gases and solids, and their temperatures and the backgrounds against which they are observed.
    (c) the temperature of a hot object and the wavelength at which it is brightest. X
    (d) the distance to a star and its angular shift against background stars.
    (e) the apparent magnitude and absolute magnitude of a star.
20. In class, we imagined looking up in the night sky at the stars in the constellation of Cygnus. The brightest stars often were very distant, while some of the closest stars are very faint. This simple observation reveals an important fact about stars. What is it?
    (a) There must be opaque clouds in the space between the stars.
    (b) The lifetimes of stars are very long.
    (c) Stars must be very similar in their luminosity.
    (d) The greater the distance to a star, the greater its luminosity.
    (e) Stars have an enormous range in their luminosities. X
21. Which of the following are (both) units used in expressing stellar distances.
    (a) parsec and astronomical unit
    (b) astronomical unit and light year
    (c) parsec and light year X
    (d) astronomical unit and Gauss
    (e) light year and Tesla
22. The difference between the apparent magnitude of a star and its absolute magnitude is a measure of a star's
    (a) distance X
    (b) luminosity
    (c) temperature
    (d) age
    (e) color
23. In class I discussed an important 11 year cycle. This is a cycle of/in
    (a) the brightness of the most luminous stars.
    (b) the time of the vernal equinox.
    (c) the tilt of the Earth's axis.
    (d) the number of sunspots. X
    (e) the strength of the Earth's magnetic field.
24. Imagine that the obliquity of the ecliptic for the Earth were actually 40 degrees, with all other astronomical properties being the same. If you lived in Iowa (same latitude) which of the following differences in basic astronomical phenomena would you observe?
    (a) a longer year, greater temperature differences between summer and winter.
    (b) winter and summer solstices would occur on different days, Sun would be lower at noon in June, higher at noon in December
    (c) planets would not be confined to a band across the sky, altitude angle of Sun at noon would be the same all year
    (d) greater temperature differences between summer and winter, Sun higher at noon in June, lower in December X
    (e) the length of the day would be greater than 24 hours, summer and winter would have more similar temperatures.
25. The fossils at the Coralville Resevoir and Lake MacBride are from the Devonian Period, 375 million years ago. What fraction of the way back to the formation of the solar system was the Devonian Period?
    (a) 1 %
    (b) 25 %
    (c) 8 % X
    (d) 75 %
    (e) 0.01 %
26. Two days out of the year, the Sun is on the celestial equator. What two days are these?
    (a) March 22 and September 22 X
    (b) June 22 and December 22
    (c) March 7 and August 7
    (d) April 7 and November 7
    (e) February 3 and July 3
27. The resolution of a telescope is determined by two quantities. What are they?
    (a) wavelength of the light and focal length of the telescope
    (b) wavelength of the light and the declination of the object being studied
    (c) diameter of the telescope and the focal length of the telescope
    (d) diameter of the telescope and perfection of the mirror
    (e) wavelength of the light and diameter of the telescope X
28. Suppose you were project manager for a manned spacecraft to Mars mission. You get to choose the years when the mission will be carried out. Would 2012 be a good year for the mission? Pick the right answer and the right reasons.
    (a) No: that year will be close to solar maximum X
    (b) Yes: Mars will be at another close approach to Earth that year.
    (c) No: Mars will be at its most distant in thirty years at that time
    (d) No: The Earth's magnetic field will be too strong for safe spacecraft operation.
    (e) Yes: in that year, a voyage out and back will be possible within 14 months.
29. Sunspots are
    (a) cool regions of different chemical composition.
    (b) cool regions of strong solar magnetic field. X
    (c) obscuring clouds on the surface of the Sun.
    (d) hot regions that emit radiation at x-rays.
    (e) isolated regions where nuclear reactions are not occurring.

30. At different times of the year we see different constellations in the evening sky. What property of the Earth and Solar System is responsible for this phenomenon?
    (a) the rotation of the Earth on its axis
    (b) the fact that all the plaents orbit the Sun in nearly the same plane
    (c) the orbital motion of the Earth around the Sun X
    (d) the Solar System is moving rapidly through space so we see different stars at different times
    (e) it takes the Sun one year to complete an orbit around the Earth.