29:50 Modern Astronomy
First Hour Exam
September 29, 1997
Form A

1. The paths of planets about the Sun are described by one of the mathematical curves listed below. Which one?
   (a) ellipse
   (b) circle
   (c) parabola
   (d) hyperbola
   (e) hyperbolic tangent
   
2. In words, Kepler's 3rd Law of planetary motion states
   (a) the further a planet is from the Sun, the faster the velocity at which it moves in its orbit.
   (b) if a force is exerted on an object, it accelerates.
   (c) planets move around the Sun in circles.
   (d) the further a planet is from the Sun, the longer it takes to complete an orbit.
   (e) the orbits of all planets lie in the same plane.
   
3. Gravity is a force which exists between objects because they possess
   (a) electric charge
   (b) angular momentum
   (c) mass
   (d) weight
   (e) a large fraction of metal
   
4. How far away from the Earth is the Moon in units of the Earth's radius?
   (a) 3 Earth radii
   (b) 10 Earth radii
   (c) 2500 Earth radii
   (d) 60 Earth radii
   (e) 300 Earth radii
   
5. There are areas on the Moon which are relatively smooth and free of craters. The term for these areas is
   (a) Terrae
   (b) Maria
   (c) impact basins
   (d) rilles
   (e) Imbres
   
6. Over a period of many years you observe the planets move against the background stars. Which of the following planets takes the longest to complete a circuit of the heavens?
   (a) Saturn
   (b) Venus
   (c) Jupiter
   (d) Mars
   (e) Mercury
   
7. At a certain time the Sun, Moon, and Earth are all in the plane of the ecliptic and lie along a line. The Earth is between the Sun and Moon. What astronomical phenomenon occurs?
   (a) total solar eclipse
   (b) annular solar eclipse
   (c) a half moon visible on the meridian at sundown
   (d) lunar eclipse
   (e) No noteworthy astronomical phenomena are seen under these conditions.
   
8. A customary ``yardstick'' or unit of length which is employed when describing distances in the Solar System is the
   (a) mile
   (b) astronomical unit
   (c) light year
   (d) parsec
   (e) planetary distance unit
   
9. What are the relative sizes (diameters) of the Earth and Moon?
   (a) The diameter of the Moon is about 1 percent the diameter of the Earth.
   (b) The diameter of the Moon is about 10 percent that of the Earth.
   (c) The diameter of the Moon is about one fourth that of the Earth.
   (d) The Moon is very nearly the same diameter as the Earth.
   (e) The Moon is roughly twice the diameter of the Earth.
   
10. The lunar Maria are smooth and have few craters. What is the reason for this?
    (a) There is no wind and water action from the Moon's atmosphere to to produce more varied topography.
    (b) The Moon is massive enough to have its gravity deform it into an almost perfect sphere.
    (c) They have been formed by lava flows after the time of maximum meteoric bombardment.
    (d) The Maria were formed more than 8 billion years ago and time has worn down the relief that originally existed.
    (e) They consist of igneous rock formations.
    
11. The star Antares is of spectral type M and has an absolute magnitude of -4. A red dwarf star is also of spectral type M and has an absolute magnitude of +10. What characteristic of the two stars must be different?
    (a) the surface temperatures
    (b) the distances
    (c) the radii
    (d) the ages
    (e) the chemical compositions
    
12. In class there was one aspect of the discoveries from the Apollo program of manned spacecraft flights which was particularly emphasized as contributing to our understanding of the whole solar system. What was this?
    (a) Radioisotope dating of rock samples from different lunar locations.
    (b) Biological experiments on the rocks which gave evidence of possible life.
    (c) Discovery that the Moon has no atmosphere.
    (d) Discovery of frozen water in lunar caves.
    (e) Suggestive evidence that the Moon had a dense atmosphere and oceans in the remote past.
    
13. Imagine an asteroid formed at the very beginning of the solar system and has had no geological activity since. Based on our discoveries from other solar system objects, what would one expect for the nature of its surface?
    (a) Covered by smooth lava flows similar to the lunar Maria
    (b) Heavily pockmarked by impact craters.
    (c) Covered by a tenuous carbon dioxide atmosphere
    (d) Have a smooth water ice crust like Europa
    (e) Not be a solid object at all, but rather a dense hydrogen-helium atmosphere
    
14. Which of the following elements is the most abundant in the universe?
    (a) hydrogen
    (b) helium
    (c) iron
    (d) oxygen
    (e) carbon dioxide
    
15. What is the age of the solar system?
    (a) 32.7 million years
    (b) 500 million years
    (c) 4.5 billion years
    (d) 10.0 billion years
    (e) 25.0 billion years
    
16. Consider the planets Jupiter, Saturn, Uranus, and Neptune as a group. Which of the following attributes is true of all of them?
    (a) All are known to harbor primitive forms of life.
    (b) They are rocky objects, some of which are smaller than the Earth and the others larger.
    (c) Much more massive than the Earth and in the outer solar system.
    (d) They are composed mainly of hydrogen and helium and are closer to the Sun than is the Earth.
    (e) They differ from the Earth in that they are orbiting Centauri A, which is a different star.
    
17. Which of the following is an accurate description of the physical characteristics of Mars?
    (a) It is very similar to the Earth in diameter and mass, closer to the Sun than the Earth, and has an extremely dense, carbon dioxide atmosphere.
    (b) Mars is much smaller than the Earth, but in nearly the same orbit, and has no measurable atmosphere.
    (c) Mars is the most massive planet in the solar system and orbits nearly 10 astronomical units from the Sun.
    (d) Mars is almost entirely hydrogen and helium and has nuclear fission reactions occurring in its atmosphere.
    (e) It is about half the diameter of Earth, more distant from the Sun, and has a tenuous carbon dioxide atmosphere.
    
18. The basis of the technique of radioistope dating is the following.
    (a) Radioisotopes change their chemical composition over time. The longer the time, the more chemically complex. By seeing what elements are present, we can deduce the age of a sample.
    (b) Radioisotopes disappear (actually convert into pure energy) over a time called a half life. By seeing how many are left, we can calculate the age of a rock.
    (c) Radioisotopes emit radiation that we can measure with Geiger counters. The older a sample, the more radioactive it is. By measuring the intensity of radiation from a sample, we can determine its age.
    (d) Certain isotopes decay into daughter isotopes with a well-defined time for the transformation to occur on average. By comparing the number of daughter isotopes to the original isotopes, one can calculate how long it has been since the rock formed.
    (e) All elements decay into hydrogen, which is the most basic element. This occurs on a half life which depends on the element. By measuring the relative amount of hydrogen and the original element, we know how old the rock is.
    
19. A question of broad interest is whether Mars has now, or has ever had life. Which of the following statements is a correct description of the status of Mars as an abode for life?
    (a) Mars at the present time does not have multicellular life, but it does have primitive one-celled life forms like bacteria.
    (b) The planet now appears to be sterile, but seems to have had a dense atmosphere and liquid water up to about 3 billion years ago.
    (c) Mars has highly developed plant life which is responsible for seasonal variations in the appearance of the planet.
    (d) The planet does not now have life, and it is almost certain that it never had life because of the absence of an atmosphere and water.
    (e) It is known that life cannot possibly exist outside the Earth.
    
20. Between the orbits of Mars and Jupiter we find
    (a) the planet Venus.
    (b) most of the known asteroids.
    (c) only empty space.
    (d) the planet Uranus.
    (e) the aphelion distances of most comets.
    
21. In words, Wien's Law states the following about light emitted by a hot object.
    (a) The hotter an object, the more reddish it appears to us.
    (b) A hot solid object emits light only at certain discrete wavelengths called spectral lines.
    (c) Objects emit no radiation at all until their temperatures reach about 2000 K.
    (d) The hotter the object, the shorter the wavelength at which it is brightest.
    (e) The object will appear dark at certain wavelengths which depend on the substance of which the object is made.
    
22. Which of the following statements about the composition of Jupiter and the Jovian planets is correct?
    (a) They differ slightly from the chemical composition of the Earth in that the elements Scandium and Zirconium are overabundant by a factor of 5-10.
    (b) The chemical compositions of Jupiter and the Jovian planets differ markedly from both the Earth and the Sun.
    (c) The most abundant elements in all of them are nitrogen and oxygen.
    (d) We have no direct information about the chemical compositions of Jupiter and the Jovian planets.
    (e) They are very similar to the Sun in chemical composition.
    
23. The main portion of the mass of Jupiter is in what form?
    (a) a heavy iron and silicon core.
    (b) gaseous hydrogen
    (c) a substance called liquid metallic hydrogen that does not exist on Earth.
    (d) liquid nitrogen.
    (e) liquid hydrogen similar to that used in rocket engines on Earth.
    
24. The largest moon of the planet Saturn is Titan. What is its claim to fame?
    (a) It is the only planetary satellite with an atmosphere.
    (b) It is the only place other than Earth where volcanos are erupting.
    (c) It is about to be disrupted and swept up into the ring of Saturn.
    (d) It is significantly larger than the next largest planetary satellite, Ganymede.
    (e) It is responsible for the formation of Saturn's ring.
    
25. The term planetesimal is used to describe
    (a) small solid objects in the early solar system which were building blocks for the present planets
    (b) small planet-like objects which presently exist in orbits between Venus and Mars.
    (c) The gas cloud from which the solar system formed.
    (d) Small objects which orbit the major planets.
    (e) Very cold, distant planets beyond the orbit of Pluto and the major planets.
    
26. Which of the following astronomical phenomena has been seriously considered as the event responsible for the extinction of the dinosaurs?
    (a) a huge solar flare which made the Earth virtually uninhabitable.
    (b) a nearby star which became a supernova, bathing the Earth in deadly radiation.
    (c) the motion of the Sun into a dense interstellar cloud with poisonous gases.
    (d) a collision between an asteroid and the Earth.
    (e) combustion of the atmosphere which the Moon had until that time.
    
27. Roughly, how many times more distant are the stars than the Sun? By ``times'' I mean a number for the ratio of the distance to a nearby star to the distance to the Sun.
    (a) tens of times more distant
    (b) hundreds of times more distant
    (c) a few hundred thousand times more distant
    (d) many millions of times more distant
    (e) We have no good idea for the distances of the stars.
    
28. Which of the following lists the basic, fundamental technique for determining distances to the nearest stars?
    (a) the inverse square law
    (b) the Baade-Wesselink technique
    (c) Use of the spectrum to determine the distance
    (d) measurement of the apparent magnitude
    (e) stellar parallax
    
29. Consider two identical stars. One is at a distance of 10 parsecs. The other is 100 parsecs away. Which of their characteristics is different?
    (a) absolute magnitude
    (b) apparent magnitude
    (c) luminosity
    (d) spectral type
    (e) mass
    
30. The Hertzsprung-Russell Diagram is a graph of
    (a) apparent magnitude versus absolute magnitude
    (b) apparent magnitude versus spectral type
    (c) absolute magnitude versus spectral type
    (d) mass versus luminosity
    (e) age versus spectral type
    
31. Space Aliens have concocted a fiendish plot to destroy the Earth and all its inhabitants. Fanning out from their base in the Oort Cloud where they continue to hold Elvis Presley, they slightly perturb the orbits of millions of Oort cloud comets so that these comets will come into the inner solar system at next perihelion passage, impacting the Earth. After hearing this information, what should be your reaction and why?
    (a) Enjoy life while you can. The comets will arrive at perihelion in about 30 years
    (b) Continue planning for the next Hawkeye football game; these comets will not arrive for millions of years.
    (c) Begin warning the authorities (they're here! they're here!); the comets are a danger but can be easily dissipated with the addition of heat which will turn them into water vapor.
    (d) Total despair; most of the comets will arrive in your lifetime and cannot be eliminated by any known force.
    (e) Consternation: the comets will not arrive in your lifetime but your great-grandchildren will have a nasty surprise.
    

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