PHYSICS 406 - Introduction to Modern Astronomy
EXAM #3
April 10, 1996
Note: Each Question counts 2 points. 80 points correspond to
100 on the grade scale in the Syllabus
Where you find the remark: (More than one answer), providing all correct
answers leads to full credit. Only one correct answer leads to 1
point. Incorrect additional answer leads to subtraction of the first
point.
1.
You observe the spectrum of a star over several days. On the first day the spectrum
behaves well and shows single lines for the elements (A). On the second day
these lines seem to be split: one line is shifted towards blue and one towards
red (B). On the third day the spectrum is similar to day 1, and on day 4 it
is similar to day 2. What is the most likely reason for this behavior?
- There must be 2 stars close to each other which orbit about each other
such that on day 2 and 4 one of the stars moves towards us and the other away
from us.
- The star is pulsating. It is at rest on day 1, expanding on day 2, at rest
on day 3 and shrinking on day 4.
- The star is cooler on day 1 and hotter on day 2.
If you have problems with this question, check Chapter VII.3B
in the Review
2. Which planets have rings? (Two for full credit. 3 or all
4 extra credit.) Short answer:
- _______________________________________________
- _______________________________________________
- _______________________________________________
- _______________________________________________
If you have problems with this question, check Chapter VI.7 in the Review
3. Inside of one of the rings around a planet we find a "shepherd
moon". Some debris is circling between the ring and the "shepherd
moon". What happens to this debris?
- The "shepherd moon" will accelerate the debris such that it is
swept away from the planet.
- The "shepherd moon" will accelerate the debris just enough that
it is lifted back into the ring.
- The "shepherd moon" will decelerate the debris such that it falls
down on to the planet.
- The debris will collide with the "shepherd moon" and stick on
it.
If you have problems with this question, check Chapter VI.7 in the Review
4. A meteor is caused by
- a star falling to Earth
- a comet streaking across the sky
- a distant nebula
- a rock falling into the Earth's atmosphere
If you have problems with this question, check Chapter VII.8C
in the Review
5. Where are most of the asteroids in the solar system?
- in the Oort cloud
- in the gap in the planet sequence between Mars and Jupiter
- inside the orbit of Mercury
- in orbit around the Earth
If you have problems with this question, check Chapter
VI.8A in the Review
6. Refer to the following figure:
In which direction does the plasma tail of the comet point?
a. b. c. d.
If you have problems with this question, check Chapter VI.8B in the Review
7. The dust tail of comets is formed in which way?
- The comet head is running ahead of its own dust debris and therefore ahead
of its dust tail.
- Tidal forces during the passage of the sun tear dust out of the comet and
pull a tail into the sunward direction.
- Dust from the comet is driven away from the sun by solar radiation pressure
and form a tail in the anti-sunward direction.
- Dust will not form a comet tail.
If you have problems with this question, check Chapter VI.8B in the Review
8. How can a comet end? (More than one answer)
- As a supernova.
- It can break up into a meteor stream.
- A comet can turn into a planet.
- A comet may hit a planet or a moon.
If you have problems with this question, check Chapter VI.8B,C in the Review
9. When meteorite pieces were found, why was this so exciting
for scientists?
- The laws of gravitation could be studied from how fast the meteorites fell
to the ground.
- Until very recently meteorites were the only matter from outer space which
could be studied in the laboratory.
- The impact of meteorites produce most of the earthquakes.
If you have problems with this question, check Chapter VI.8C in the Review
10. Why is the observation of plenty of Iridium in 65 million
year old layers in geological formations of the Earth a clue for a huge meteorite
impact as the reason for the dinosaur extinction?
- Iridium is poisonous for dinosaurs.
- Iridium is much more abundant in meteorites than in the Earth's crust.
- Iridium is created in the melting of the Earth's crust during a meteorite
impact.
- Iridium is dug out of the Earth's interior during a meteorite impact.
If you have problems with this question, check Chapter VI.8C in the Review
11. The photosphere of the sun is
- the region where the energy is produced
- the layer of the sun from which most of the visible light comes
- the hottest part of the sun's atmosphere
- the sun's interior
- he region filled with the solar wind
If you have problems with this question, check Chapter VIII.2A in the Review
12. The Enterprise arrives at a star system with a blue star.
The crew finds that the star has approximately the same size as the sun. What
is the luminosity of this star like?
- It is less luminous than the sun.
- It has the same luminosity as the sun.
- It is more luminous than the sun.
- Can't tell, luminosity has nothing to do with colors.
If you have problems with this question, check Chapter VII.2A in the Review
13. What are the two elements that make up most of the material
of the Sun?Short answer
- _______________________________________________
- _______________________________________________
If you have problems with this question, check Chapter VII.2C
in the Review
14. To determine the total energy flux from the sun we measure
- the energy flux through 1 square meter at the distance of the Earth
- the temperature on the Earth's surface
- the size of the sun
- the amount of light reflected from the moon
If you have problems with this question, check Chapter VII.1D in the Review
15. How do we know what the sun consists of?
- from lines in the solar spectrum
- from a spaceprobe we have sent into the sun
- from the color of the sun's surface
- from the shape of the sunspots
If you have problems with this question, check Chapter
VII.2C in the Review
16. Which of the following is true? The solar energy captured
by the Earth is
- much more than the energy consumed by humans on Earth
- just as much as the energy consumed by humans on Earth
- much less than the energy consumed by humans on Earth
If you have problems with this question, check Chapter VII.1D in the Review
17. Why is a high temperature needed for energy production
in the core of the Sun?
- Hydrogen will not combine with oxygen at a low temperature.
- Energy is needed to overcome electrical repulsion of hydrogen nuclei.
- Electrons will not recombine at low temperatures.
- The force of gravity is greater at high temperatures.
- Speeds are less at high temperature, so there is more time for reactions
between nuclei.
If you have problems with this question, check Chapter VIII.1A in the Review
18. Name 2 possible ways to ionize neutral interstellar gas
close to the sun. (all 3: extra credit) Short answers
- _______________________________________________
- _______________________________________________
- _______________________________________________
If you have problems with this question, check Chapter IX.2 in the Review
19. We know that the Sun's energy does not result from a chemical
burning of coal. Why?
- There is no ash on the bright surface of the sun.
- There is no smoke coming out of the sun.
- No carbon absorption lines are found in the sun's spectrum.
- Even if the entire sun were made out of coal and oxygen, it would only have
had energy for 10,000 years.
If you have problems with this question, check Chapter VIII.1A in the Review
20. The bow shock of the Earth's magnetosphere is
- a magic shield against Klingon weapons around the Earth
- the supersonic boom of the Earth's magnetic field in the solar wind
- the region where the aurorae originate
- the region around the Earth where spacecraft usually reach supersonic speed
when launched from the Earth
If you have problems with this question, check Chapter
VIII.2D in the Review
(new Version on WWW!!)
21. On the Earth we cannot control nuclear fusion yet, since
we cannot contain the hot plasma which is needed for the reaction. What keeps
the hot nuclear oven contained inside the sun?
- electrical forces
- the sun's magnetic field
- the pressure resulting from the weight of material above
- the centrifugal force from the sun's rotation
- a Warp drive containment field
If you have problems with this question, check Chapter VIII.1A, B in the Review
22. Granulation on the Sun's surface is a direct evidence
of energy transport in the outer layers of the sun by
- electric currents
- convection
- heat radiation
If you have problems with this question, check Chapter VIII.2A in the Review
23. Which particles produced inside the sun in nuclear fusion
are messengers which make their way directly to the Earth?
- g-rays
- neutrinos
- helium nuclei
- positrons
If you have problems with this question, check Chapter VIII.1A, C in the Review
24. Helioseismology is
- the measurement of pressure pulses of the solar wind
- a theory which connects sunspots with earthquakes
- the use of pulsations of the sun to gather information about its interior
similar to using earthquakes
- a theory to explain the dance of the planets around the sun
If you have problems with this question, check Chapter VIII.1C in the Review
25. When an astronomer talks about a Blackbody she/he means
- the same as a Black Hole
- an object which does not reflect any light, but emits radiation due to
its temperature
- Batman at night
- the night sky
If you have problems with this question, check Chapter VII.2A in the Review
26. The sunspots are darker than the surrounding regions because
- they reflect less light
- they contain the ash from the burning processes in the sun
- they are cooler than the rest of the surface
- they are hotter than the rest of the surface
- they are holes in the solar surface
If you have problems with this question, check Chapter VIII.2A in the Review
27. How do we know that the corona is has a temperature of
1-3 million degrees?
- Because it is blue.
- Spectral lines from highly ionized iron (lost many electrons) are observed
in the corona
- The corona is the brightest part of the sun
- A spacecraft has been sent into the corona
If you have problems with this question, check Chapter VIII.2C in the Review
28. To observe stars in the process of formation in the dusty
interstellar clouds you should use
- a. an X-ray telescope.
- b. an ultraviolet telescope.
- c. an infrared telescope.
If you have problems with this question, check Chapter X.1 in the Review
29. If we obtain a spectrum from a bright nebula with interstellar
gas we get
- a continuous spectrum like from an incandescent body
- a spectrum with bright lines
- nothing, interstellar gas does not emit any light
If you have problems with this question, check Chapter IX.4 in the Review
30. If you were at "you are here" in the following
figure, what would you see?
- The star would look redder than it really is.
- A blue reflection nebula.
- Absorption lines produced by the dust particles.
- A red interstellar gas cloud.
If you have problems with this question, check Chapter IX.4 in the Review
31. Assume a star with ten times the mass (i.e. ten times the
fuel) of the sun. According to the Mass-Luminosity relation this star is about
3000 times as luminous as the sun. This star will
- reach the same age as the sun
- live longer than the sun
- live shorter than the sun
If you have problems with this question, check Chapter VII.3B and X.3B in the
Review
32. Stars are formed out of thin interstellar gas. Which of
the following conditions are favorite for star formation? (More than one)
- a high temperature of the gas
- a fast rotation of the nebula
- a low temperature of the gas
- a strong magnetic field
- a high density of the gas
- a low density of the gas
If you have problems with this question, check Chapter X.1 in the Review
33. You see two stars (A and B) in the sky that appear equally
bright. From an astronomy book you learn that star A is 3 times as far away
as star B. What do you conclude about the luminosity of the two stars?
- The luminosity of both stars is the same.
- B is 9 times more luminous than A
- B is 3 times more luminous than A
- A is 9 times more luminous than B
- A is 3 times more luminous than B
If you have problems with this question, check Chapter VII.1A, D in the Review
34. What is plotted on a Hertzsprung-Russell diagram?
- Luminosity and temperature of stars.
- Mass and size of stars.
- Temperature and distance of stars.
If you have problems with this question, check Chapter VII.4A in the Review
35. Where on the Hertzsprung-Russell diagram below do you find
the White Dwarfs?
a. b. c. d.
If you have problems with this question, check Chapter VII.4A in the Review
36. Where on the Main Sequence in the Hertzsprung-Russell diagram
above do you find the stars that live for the longest time?
a. b. c. d.
If you have problems with this question, check Chapter VII.4A in the Review
37. A (cool) red giant star has the same luminosity as a (hot)
blue giant. What can you conclude?
- This cannot be true. One of the stars is cheating.
- The red giant is the bigger star.
- The blue giant is the bigger star.
- Both stars have the same size.
If you have problems with this question, check Chapter VII.2A, 4A in the Review
38. The sun is shining so steadily because the pressure generated
by heat from nuclear fusion in the sun's core is just balancing the weight of
the material above. Imagine that by a fluctuation there is not enough heat generated
for a short while. What happens in the sun's core?
- The core will be compressed and therefore become hotter, which will increase
the nuclear reactions again.
- The core will shrink and the nuclear reactions will cease altogether.
- The core will expand in order to re-ignite the nuclear reactions.
- Heat will flow from the outer layers of the sun into the core to re-ignite
the nuclear reactions.
If you have problems with this question, check Chapter VIII.1A in the Review
39. The collapse of a gas cloud into star formation can be
triggered by
- a star passing through the cloud
- a shock wave from a supernova compressing the cloud
- magnetic forces
- centrifugal forces
If you have problems with this question, check Chapter X.1 in the Review
40. What is the reason that Population I stars have more heavy
elements than Population II stars?
- Population I stars are second generation stars and inherited the heavy
elements from material processed already in earlier stars.
- Population I stars are more massive than Population II stars.
- Population II stars have lost all their heavy elements to their planets.
- Population I stars have been bombarded with many meteorites which provided
the heavy elements.
- Population I stars have been treated by an alien spaceship with an any-ion
beam.
If you have problems with this question, check Chapter VII.2B in the Review
Bonus
Question 1: Refer to the drawing. Close to the sun, interstellar gas atoms loose
one of their electrons and become ions. Imagine a situation where the interplanetary
magnetic field is perpendicular (out of the plane in the drawing) to the solar
wind while taken along with the wind. Which velocities can the interstellar
ions gain from the solar wind and the magnetic field?
- Interstellar ions are picked up with exactly the solar wind velocity.
- Interstellar ions can reach up to twice the solar wind velocity after they
are picked up.
- Interstellar ions will only move along the magnetic field with their original
velocity.
- Interstellar ions won't move at all, because they are not influenced by
the solar wind and the magnetic field.
If you have problems with this question, check Chapter IX.2 in the Review
Bonus Question 2: The hydrostatic equilibrium in the sun is
maintained between
- electrical forces and gravity
- gas pressure and electrical forces
- gas pressure and nuclear forces
- gas pressure and the weight of material above
If you have problems with this question, check Chapter VIII.1B in the
Review