Download Midterm Exam: Chs. 1-3, 7-11

EXAM I
Astronomy 311 January 9, 2014
Professor Menningen
Name:_________KEY___________
You have a full 120 minutes to complete the exam. The only allowed tool is a calculator.
Section I. (15 pts). Follow the instructions below to fill in the depicted star chart.
(a) (8 pts) A star chart for January 9 at 10:00pm appears below. Draw lines connecting the
stars of the following constellations on the provided star chart, and label them:
BIG DIPPER
CEPHEUS
TAURUS
LEO
(b) (2 pts) Use a dotted line to indicate the WINTER TRIANGLE and label it.
(c) (5 pts) Label the following stars on the chart:
POLARIS
CAPELLA
REGULUS
BETELGEUSE
PLEIADES CLUSTER
January 9, 2014
Little Dipper
Cepheus
Polaris
Cassiopeia
Leo
Capella
Andromeda
Auriga
Regulus
Pleiades
Taurus
Procyon
Betelgeuse
Winter
Triangle
Sirius
Aldebaran
Orion
Section II. (25 pts). Show all of your work, including the symbolic formula you are using,
when solving the following problems. Include the appropriate units in your answer.
A.
When the space shuttle (m = 78,500 kg) approaches the International Space Station
(m = 427,000 kg) for docking, the two centers of mass are 8.5 m apart. What is the force of
attraction between them? Report your answer in Newtons.
(6 pts)
F G
m1m2
r2
  6.67  1011 N  m 2 /kg 2 
 78,500 kg  427,000 kg 
2
8.50 m 
F  3.09  102 N  0.0309 N
B.
Astronomers detect a large planet hurtling towards our solar system from somewhere
in our galactic neighborhood and would like to determine the mass of the planet.
Fortunately this planet already has a moon orbiting a distance of 0.000835 AU with a period
of 0.0139 years. What is the mass of the planet in kg? {Depending upon how you approach
this problem, you may need to know 1.0 AU = 1.50×1011 m, 1.0 yr = 3.156×107 s,
1.0 solar mass = 1.99×1030 kg, or G = 6.67×10−11 N·m2/kg2}
(7 pts)
a3
From Kepler's Third Law, M  2 if you stick to AU and years, so
P
 0.000835 AU 
M
2
 0.0139 y 
3
 3.01  106 M   3.01  106 1.99  1030 kg   6.00  10 24 kg
or you can use the general form of Kepler's law in meters and seconds:
M
4 2  0.000835  1.50  1011 m 
3
4 a

 6.04  1024 kg
2
2
GP
 6.67  1011 N  m2 /kg 2  0.0139  3.156  107 s 
2
3
C.
When would it be the best time of the year to view a star with a right ascension of 18
hours 0 min 0 sec? Explain your answer by using the diagram. The north pole of the Earth
is pointing up out of the page in the diagram. Fill in the dates March 21, June 21, September
21, and December 21 in the boxes in the diagram and label the hours of right ascension on
the celestial sphere. [The celestial sphere is always centered on the Earth, but I drew it only for the case
(5 pts)
when the Earth is at its leftmost position in the diagram.]
Vernal equinox
0 h 23
1
Celestial Sphere
2
For when the Earth is
in the leftmost position
in the diagram
Answer and written explanation:
The best time of the year would be
June 21 or the summer solstice
because that star would be high in the
sky at midnight.
22
3
21
4
earth
5
19
sun
6
18
December 21
June 21
7
17
8
16
March 21
9
15
10
14
11
D.
20
September 21
12
13
Suppose you are standing on Mars and observing Phobos, one of its moons, move against
the background stars. You might find some of the following information to be helpful:
Diameter of Phobos: 22.2 km Orbit semi-major axis: 9377 km Orbit period: 7.66 hours
{The circumference of a circle of radius r is 2r. }
(7 pts)
a) By how far will have Phobos moved, in degrees, against the background stars during the
span of one hour?
Find the angle it moves:
 360 
 1.0 h   47.0
 7.66 h 
 t  
b) How much time will it take for Phobos to move 10° (about the distance across a closed
fist held at arm’s length) against the background stars?
Now find the time it will take for the moon to travel 10:
t

60 min
 7.66 h 
 10  

0.2128
h

 12.8 min


h
 360 
Section II. (28 pts) Please answer True (+) or False (O).
+ 1. An astronomical unit or 1 AU is a unit of length equal to the average distance
____
between the Sun and Earth.
O 2. As the Earth rotates, the zenith of a person standing on the equator sweeps out the
____
ecliptic plane celestial equator.
O 3. To navigators in the northern hemisphere, their latitude in degrees is equal to the
____
angle between their meridian northern horizon and the north celestial pole.
+ 4. A planet's sidereal orbital period is different from its synodic period because the
____
Earth orbits the Sun.
O 5. When observing planetary motions from Earth, the phrase "retrograde motion"
____
refers to motion of the planet away from the Sun during part of its orbit. a slow
westward motion of the planet from night to night against the background stars.
+ 6. The third quarter moon rises at close to midnight local (solar) time.
____
O 7. The protosun became a full fledged star at about the same time the planets began to
____
form. Once thermonuclear reactions began.
+ 8. Galileo disproved Ptolemy’s model of the solar system by observing the phases of
____
Venus through a telescope.
O 9. The greenhouse effect is the absorption of solar ultraviolet planetary infrared
____
radiation by gases in planetary atmospheres leading to atmospheric heating.
O 10. Because of the unique tilt of the equator of Mars with respect to its orbital plane,
____
Mars experiences almost no seasonal variation in its weather similar to Earth.
+ 11. The orbital period P of particles moving around the rings of Saturn depends on
____
their distance R from the center of the planet such that P2 is proportional to R3.
O 12. The heating of the interior of Io is caused by thermal heating from Jupiter, because
____
Jupiter emits more radiation than it receives from the Sun. continuous tidal
distortion by Jupiter and the other moons.
+ 13. Compared to those on Earth, the expected seasonal changes on Uranus will be very
____
much exaggerated, because the spin axis is almost in the orbital plane.
O 14. A comet's gas and ion tail always trails along the orbital path because of the
____
comet's motion. point directly away from the Sun regardless of the comet’s motion
Section III. (3 pts each, 132 pts total). Answer the following questions by writing the
appropriate letter in the blank to the left of the question number. Choose the BEST answer.
____ 15. If Venus has an angular diameter of 30 arcseconds when viewed from Earth at a
particular time, how does this compare with the typical 0.50° angular diameter of
the Moon?
Half a degree is about 30 arcminutes
a.1/3600 as large
b. 1/30 as large
or 30  60  1800 arcseconds so
c. 60 times larger
30 arcseconds
1
d. 1/60 as large
1800 arcseconds

60
____ 16. The best method for estimating the age of the surface of a celestial body with a solid
surface such as a terrestrial planet or a moon (other than bringing rock samples back to
Earth) is based on the idea that
a. volcanic activity occurs at a known rate, so the fewer volcanoes observed, the
younger the surface.
b. planets and other bodies are subject to impacts from space at a known rate,
so the fewer the number of craters, the younger the surface.
c. lithospheric plates form at a known rate, so the more plates observed, the
older the surface.
d. craters are weathered at a known rate, so the more eroded the craters, the
older the surface.
____ 17. At what approximate value of declination was the Sun on December 21 this year?
a. 23.5°
b. 45°
c. 0°
d. −23.5°
____ 18. The two bright stars in the constellation Gemini, the Twins, are Castor (right ascension
7h 33m, declination +31° 56’) and Pollux (right ascension 7h 44m, declination +28° 5’).
From these coordinates you can see that
a. Pollux is slightly southeast of Castor. b. Pollux is slightly northeast of Castor.
c. Pollux is slightly northwest of Castor.
d. Pollux is slightly southwest of Castor.
____ 19. The ecliptic is
a. the plane midway between the celestial poles.
b. the imaginary line stretching from due north to due south that passes through the
zenith.
c. the point directly above the observer's head.
d. the path of the Sun across the celestial sphere over the course of a year.
____ 20. The Earth would NOT have seasons if
a. its axis of rotation were perpendicular to its equatorial plane.
b. its equatorial plane were perpendicular to its orbital plane.
c. its axis of rotation were perpendicular to its orbital plane.
d. the observer's zenith were perpendicular to the Earth's orbital plane.
____ 21. If the Moon is located at the vernal equinox on September 20, what is the phase of the
Moon?
a. new b. waxing crescent c. third quarter d. gibbous e. first quarter f. full
____ 22. If a tenth planet were to be discovered with a sidereal period of 200 years, what would
be the semimajor axis of its orbit?
a. 34.2 AU
P 2  a3 if the units are kept in years and AU so
b. 2828 AU
2
c. 200 AU
a  3 P 2  3  200 y   34.2 AU
d. 342 AU
____ 23. What process heated the early solar nebula as it slowly condensed toward a central
protosun?
a. rotational energy transferred to heat by friction between particles as the
nebula slowly revolved around its center
b. release of heat by collisions of particles as they gain kinetic energy in falling
toward the center of the nebula
c. release of heat as molecules formed and as gases condensed into ices
d. thermonuclear fusion in the protosun, followed by radiated heating of the nebula
____ 24. Which of the following is a necessary condition for lunar or solar eclipses?
a. The Earth must be on the celestial equator.
b. The Sun must be on the celestial equator.
c. The Sun must be close to or crossing the ecliptic plane.
d. The Moon must be close to or crossing the ecliptic plane.
____ 25. The occasional retrograde motion of Mars against the background stars is the result of the
a. observation of a slowly moving Mars from a more rapidly moving Earth
b. observation of a rapidly moving Mars from a more slowly moving Earth.
c. variable speed of Mars because its orbit is elliptical.
d. observation of Mars from the rapidly rotating Earth.
____ 26. Which of the following is NOT one of Kepler’s laws?
a. Planets move in elliptical orbits with the sun at one focus.
b. Every planet gravitationally attracts the sun and every other planet.
c. A planet sweeps out equal areas in equal amounts of time.
d. The orbital period squared of a planet is proportional to the semimajor axis cubed.
____ 27. To which of these phenomena do Newton's laws of motion NOT apply?
a. a high jumper at the Olympic Games
b. a spacecraft in circular orbit around Earth, such as communication satellites
c. light travel between Sun and Earth
d. space vehicles on a journey to Saturn (for example, Cassini)
____ 28. The term "synodic month" refers to the
a. time from one lunar eclipse to the next.
b. time from new moon to new moon.
c. month containing Easter, as defined by the ecclesiastical calendar.
d. time over which the Moon completes one orbit around Earth, relative to the stars.
____ 29. Suppose that a planet of the same mass as Earth were orbiting the Sun at a distance of
10 AU. The gravitational force onmthis
planet due to the Sun would be
1m2
G
2
a. 100 times the gravitational force
2 the Sun
2 exerts on Earth.
1 AU 
Fnew
rnew
rold

1
1
b. 10 times the gravitational
 force theSun2 exerts
 on Earth.2 
so Fnew 
Fold
m1the
m2 Sunrnew
Fold force
100
100
c. 1/10 of the gravitational
exerts
on
Earth.
10
AU


G 2
d. 1/100 of the gravitational force
rold the Sun exerts on Earth.
____ 30. Suppose that observers using the Hubble Space Telescope detect around several solar-type
stars the presence of planets with the following characteristics: low density, large size,
polar diameters shorter than equatorial diameters, fluid surfaces, rapid rotation. How
would these planets be classified, in terms of our solar system?
a. asteroids
b. terrestrial planets
c. Jovian planets
d. comet nuclei
____ 31. The best way to measure the mass of a planet is to measure the
a. period and orbit radius of an orbiting moon.
b. speed of the planet in its orbit around the Sun.
c. size and rotational speed of the planet.
d. composition of the planet using spectroscopy.
____ 32. At what average speed does the Sun appear to move with respect to the stars in order
to move through one full circle in one year?
a. about 1° per day
360o
 0.986o /day  1o /day
b. 15° per hour
365 d
c. about 13° per day
d. The Sun never appears to move with respect to the stars in the sky.
____ 33. More than any other, which physical parameter probably controlled the early evolution
of the planetary system and dictated the characteristics of the planets that eventually
formed?
a. overall rotation of the nebula
b. density of hydrogen gas in the nebula
c. mix of chemical constituents
d. temperature distribution within the nebula
____ 34. A theory of the origin of the solar system must take into account all important general
properties of the planets. These include three of the four properties listed below. Which
one is NOT an important general property of the planets?
a. The planets are grouped by size and composition into two general groups:
terrestrial and Jovian.
b. The planets all have cratered surfaces.
c. The terrestrial planets all orbit much closer to the Sun than do any of the Jovian
planets.
d. All of the planets orbit the Sun in the same direction and in nearly the same plane.
____ 35. In the year 2005, an inhabitant of a planet orbiting a distant star observed the flash of
the first nuclear explosion on Earth, which occurred in July 1945. Approximately how
far away is his solar system from Earth? (1 pc = 3.26 ly)
a. 60 pc
The planet must be 60 light years from Earth,
b. 6.0 pc
1 parsec
c. 18.4 pc
d  60 ly 
 18.4 pc
d. 196 pc
3.2616 ly
____ 36. The theory that seems to account most satisfactorily for the origin of the Moon at the
present time is that
a. a large object collided with Earth and ejected the material that formed
the Moon.
b. the Moon formed from material spun off from Earth when Earth was molten
and spinning rapidly, early in its history.
c. the Moon formed by accretion elsewhere in the solar system and was captured
later by Earth.
d. the Moon formed from material already in orbit around Earth.
____ 37. Astronomers sometimes announce that they have discovered a new solar system beyond
our own, or a new galaxy beyond our own. Which choice correctly describes the terms
"solar system" and "galaxy"?
a. A solar system is a large assemblage of stars similar to the Sun, whereas a galaxy is
much larger and consists of all different types of stars.
b. A solar system consists of an immense number of stars (i.e., suns), and a galaxy is a
cluster of many such systems.
c. A galaxy consists of planets and other objects orbiting around a single star,
whereas a solar system is a system consisting of an immense number of stars.
d. A solar system consists of planets and other objects orbiting around a star,
whereas a galaxy is a system consisting of an immense number of stars.
____ 38. Which planets rotate about their axes in a retrograde direction, opposite to their orbital
directions?
a. Mercury, Mars, and Uranus
c. Venus, Uranus, and Pluto
b. Venus, Uranus, and Neptune
d. Mercury, Venus, and Neptune
____ 39. The 1908 Tunguska event was
a. a giant fireball in Siberia created by the impact of a small asteroid.
b. an intense meteor shower that occurred when Earth passed through the tail of
comet Tunguska.
c. collision of a series of comet fragments with the planet Jupiter.
d. the successful landing of a Russian space probe on the surface of Venus.
____ 40. What does the surface of Europa, a moon of Jupiter, look like?
a. entirely ice, with fractures and ridges going in every direction and no features
more than about 100 m high
b. entirely ice, with light and dark areas containing many impact craters and parallel
ridges up to about 1 km high
c. rocky and densely cratered, except for a few large, dark, relatively uncratered plains
d. We don't know; the surface is hidden below a dense layer of clouds.
____ 41. The physical structure of Saturn's rings is
a. a thin, solid ring of rock and ice that is partly transparent.
b. hot, ionized gas in a current sheet within the planet's magnetosphere.
c. a thin but extensive gas cloud over the equator.
d. a sequence of many hundreds of separate rings made of ice and
rock particles.
____ 42. What causes the banded structure on Jupiter's visible "surface"?
a. an underlying rising and falling convection pattern, stretched into bands by
Jupiter's rapid rotation.
b. an underlying north-south flow pattern, stretched into bands by Jupiter's rapid
rotation.
c. the "sweeping" of Jupiter's clouds through magnetic field lines from Jupiter's
magnetosphere.
d. the breakup of strong eastward flows, due to Jupiter's rapid rotation by
underlying mountain ranges.
____ 43. Water has been discovered on Mars. In what state is it likely to be?
a. only as atmospheric water vapor, never condensing out as liquid water or solid ice
b. as a liquid flowing along the numerous flood valleys and meandering stream beds
c. in permafrost, polar icecaps, and atmospheric vapor
d. as a liquid and vapor in numerous hot surface fissures and geysers
____ 44. The severe atmospheric conditions that quickly destroyed spacecraft, which were softlanded on the surface of Venus, were
a. intense sunlight, including UV, very high pressures, and very low temperatures.
b. very low temperatures, a near vacuum, and corrosive alkaline clouds and mist.
c. high temperatures, low atmospheric pressure, and intense UV radiation from the Sun.
d. high temperatures, high pressures, and corrosive acid clouds and mist.
____ 45. What mechanism controls the direction in which a comet's ion tail is aligned in space?
a. The flow of solar wind past the comet's head.
b. The gravitational attraction of the tail material toward the Sun.
c. The gravitational attraction of the tail material toward the giant planet Jupiter.
d. Its direction of motion because the tail simply trails behind the comet in its orbit.
____ 46. Which of the following statements is NOT true for asteroids?
a. Some asteroids occupy the same orbit as Jupiter.
b. The total mass of all asteroids is much smaller than the mass of the Earth.
c. Only a minority of all asteroids are actually in the "asteroid belt."
d. Some asteroids have orbits that carry them inside the Earth's orbit.
____ 47. The densities of the four Galilean satellites of Jupiter are
a. all low, typical of rock and ice, because they formed in the outer solar system.
b. very low because, as with Jupiter, they are composed mostly of hydrogen.
c. high (rocky) for the two inner satellites, low (rock and ice) for the two
outer satellites.
d. all high, typical of rock, because they are planetary satellites (similar to
our Moon).
____ 48. Neptune's predominantly blue appearance is caused by
a. preferential scattering of the blue end of the solar spectrum by Neptune's
atmosphere, similar to the process that causes the blue sky on Earth.
b. the absorption of reflected sunlight at the red end of the spectrum
by methane in its atmosphere.
c. the fact that solar light has lost much of its red light by scattering in the interplanetary medium by the time it reaches Neptune.
d. auroral emissions caused by solar wind particles exciting the atoms and
molecules in Neptune's high atmosphere.
____ 49. The Great Red Spot is
a. a large, long-lived, high-pressure storm in Jupiter's atmosphere.
b. the colored polar cap of Jupiter.
c. clouds of dust-laden gas upwelling above the top of a massive volcano on
Jupiter’s surface.
d. a type of storm in Jupiter's atmosphere that can last for a few months at a
time before disappearing.
____ 50. Triton, the largest moon of Neptune, closely resembles
a. the Galilean satellite Io
c. the terrestrial planet Mercury
b. Pluto and other large Kuiper belt objects
d. an iron-rich asteroid.
____ 51. What is Olympus Mons?
a. A gigantic volcano on Mars that was formed as hot material rose from the deep
interior of the planet and forced the surface upward as it reached the crust.
b. A relatively high altitude region of Venus’ surface that is dotted with congealed
lava domes and other volcanic features.
c. The largest satellite of Saturn, featuring a thick nitrogen atmosphere and a weather
system driven by liquid methane.
d. a region of Triton, a moon of Neptune, where nitrogen geysers were observed
erupting hundreds of meters above the surface and leaving dark streaks of “soot”
____ 52. The scarps on Mercury’s surface are
a. ring-like features that formed upon impact around many of its craters.
b. jumbled mountains that suggest Mercury was blown apart by a large impact
and then reassembled by gravity.
c. rows of active volcanoes that formed because of the large tidal forces exerted
on Mercury by the Sun.
d. enormous, long cliffs that formed when the planet cooled and shrank.
____ 53. A friend who says that he is an astronomer claims that he was outside at midnight a few
weeks ago looking at Mercury. What should be your response?
a. “Oh, you must have been in Australia or South America since Mercury can
be seen at midnight only from the southern hemisphere."
b. "You must be mistaken, because Mercury NEVER appears in our midnight sky."
c. "Really! Have you just purchased a new telescope? Mercury can be seen at
midnight only through a telescope."
d. "Congratulations, you have been fortunate enough to see Mercury on a very rare
occasion."
____ 54. Planetary geologists agree that the amount of water in the rocks of Venus and Earth
plays a key role in explaining the differences in surface features between the two
planets because
a. the wetter rocks on Venus absorb more CO2.
b. the wetter rocks on Earth allow a thinner crust with plate tectonics.
c. the drier rocks on Venus are softer and melt at a lower temperature.
d. the drier rocks on Earth are stiffer and melt at a higher temperature.
____ 55. One of the striking features of the overall surface of Mars is
a. the presence of active volcanoes and lava flows over the whole surface, including
near to the poles, where these flows melt the icecaps regularly.
b. the remarkable similarity of surface features across the whole of the planet,
including uniform distribution of craters and ancient river valleys.
c. the uniform distribution of water-ice frost over the whole surface, hidden in the
shade of rocks, both winter and summer.
d. the two very distinct hemispheres, one of them lower and smoother than its
counterpart and almost free of craters.
____ 56. Saturn appears to emit heat as infrared radiation in excess of the energy absorbed from
sunlight. The most likely major cause of this heating is
a. condensation of helium into droplets that fall into the planet, releasing
gravitational energy as heat.
b. the radioactive decay of naturally occurring isotopes in the atmosphere and
interior of Saturn.
c. energy released from the continuous shrinking and condensation of this fluid planet.
d. remnant heat from the original formation of the planet.
____ 57. A meteor shower occurs when
a. the Earth’s orbit crosses through the asteroid belt.
b. the Earth passes through debris strewn along a comet's orbit.
c. a meteor is about to get married.
d. the Earth passes through a portion of the spiral arm of the Milky Way galaxy.
____ 58. What is the Roche limit?
a. The maximum size of an orbiting moon.
b. The minimum orbit distance of a moon before tidal forces break it up.
c. The minimum mass that a ring system can contain in a stable configuration.
d. The maximum speed of an orbiting moon.