NAME __________________________________ LAB # _________________________
Astronomy 1001 - Midterm #2 - April 4th Dr. Liliya Williams - Spring 2005
Read Instructions Carefully:
1. MARK THE ANSWERS YOU CHOOSE ON THIS TEST AS IT IS YOUR ONLY
OPPORTUNITY TO CHECK WHICH ANSWERS YOU GOT RIGHT OR
WRONG. This will not be done for you at a later time in the departmental office.
Exams will be returned in lab; be sure to include your LAB section number on each
page where indicated. Without your lab NUMBER, the return of your exam will be
delayed as well as the posting of your score.
2. Print your NAME, ID # and SECTION # on the bubble sheet where appropriate. Your
SECTION # should read 01. All three items are necessary for the proper scoring and
computer transfer of your scores.
3. Use a pencil, make your marks dark and neat, and erase thoroughly.
4. There is only one answer to each question. Choose the best answer.
5. You may use this test for scratch paper.
6. One page (1 side) of notes is allowed for the exam.
I. Multiple Choice (4 pts each)
1. The spectrum of our Sun
(a) has no absorption lines
(b) can be approximated by a blackbody spectrum at a temperature of 6000K
(c) has absorption lines due to chemical elements not found anywhere else
(d) is completely different from spectra of other stars
(e) has never been looked at
2. Sunspots appear to be darker than their surroundings because
a) they are regions of lower temperatures
b) of obscuring clouds in the solar atmosphere
c) they contain no magnetic fields
d) of interplanetary dust and gas
e) they are holes in the corona with no light coming from them
3. The temperature of Sun's corona is
(a) similar to the temperature of its photosphere
(b) much higher than the temperature of its photosphere
(c) much lower than the temperature of its photosphere
(d) unknown
(e) varies with a 24 hour period
4. Normal stars age and evolve because they
(a) gradually use up their nuclear fuel
(b) cool off with time
(c) form planets
(d) collide with other stars
(e) gradually use up their rotational energy
5. When an electron in an atom goes from a higher energy state to a lower energy state, the atom
(a) emits a photon of a specific frequency
(b) absorbs a photon of a specific frequency
(c) absorbs several photons of a specific frequency
(d) can emit a photon of any frequency
(e) can absorb a photon of any frequency
6. Astronomers can determine what stars are made of by
(a) detecting and identifying their spectral lines
(b) studying their evolution
(c) measuring the speed of the light they emit
(d) weighing them using Kepler's laws
(e) measuring their Doppler shifts
7. During the formation of a star, contraction stops when
(a) the star collapses to a black hole
(b) hydrogen burning becomes the dominant energy source
(c) the star becomes a white dwarf
(d) helium burning becomes the dominant energy source
(e) the star begins to pulsate
8. Three stars, Tom, Dick and Harry, are plotted on the HR diagram. Which one of the following statements is true?
(a) Harry is the smallest of the three stars
(b) Tom will live longer than Dick
(c) Dick will live longer than Tom
(d) Tom is the least luminous of the three
(e) Harry is the least luminous of the three
9. Referring to the same three stars on the HR diagram, pick the correct statement
(a) Tom is burning Helium in the core
(b) Harry is burning Helium in the core
(c) Tom is burning Hydrogen in the core
(d) Dick is burning Hydrogen in the core
(e) Dick has the highest core temperature of the three stars
10. Helium flash happens
(a) to low mass stars as they form and become Main Sequence stars
(b) to high mass stars as they become Red Giants
(c) to low mass stars during their Red Giant stage of evolution
(d) when high mass stars begin to fuse Helium into Iron in their cores
(e) when low mass stars begin to fuse Helium into Iron in their cores
11. Nova happens as a consequence of
(a) carbon fusion inside White Dwarf stars
(b) Red Giant stars running out of Helium in their cores
(c) Silicon to Iron fusion on the surface of the White Dwarf stars
(d) Hydrogen to Helium fusion on the surface of the White Dwarf stars
(e) Planetary Nebula getting very hot
12. A star with a Main Sequence Mass of 10 Solar Masses will probably end up as
(a) planetary nebula
(b) black hole
(c) neutron star
(d) white dwarf
(e) black hole or neutron star
13. 1.4 solar masses is the maximum mass for
(a) main sequence stars
(b) black holes
(c) neutron stars
(d) white dwarfs
(e) gas giant planets
14. Nuclear reactions in the core of the Sun require high temperatures because
(a) Helium does not exist at low temperatures
(b) Hydrogen does not exist at low temperatures
(c) Hydrogen atoms need to be ionized
(d) similarly charged Hydrogen nuclei need to be able to overcome electrostatic forces of repulsion
(e) all of the above
15. Sun is powered by
(a) nuclear reactions converting H to He
(b) nuclear reactions converting Uranium to Lead
(c) chemical reactions, similar to burning of coal
(d) mechanical energy that comes from Sun's rotation
(e) electromagnetic energy
16. Our Sun is a
(a) white dwarf star
(b) protostar
(c) main sequence star
(d) red giant star
(e) Cepheid star
17. Neutrinos are
(a) a type of neutron
(b) a type of photon produced in the core of the Sun
(c) neutral atoms
(d) low mass particles produced in the core of the Sun
(e) small furry creatures that live on Mars
18. HR diagram of a star cluster can be used to determine cluster's
(a) age
(b) velocity away or towards us
(c) chemical composition
(d) gas content
(e) all of the above
19. Binary stars provide astronomers with their primary method for measuring stellar
(a) luminosities
(b) masses
(c) chemical composition
(d) radii
(e) temperatures
20. What causes the radio pulses of a pulsar?
(a) the star vibrates
(b) as the star spins, beams of radio radiation sweep through space. If one of the beams crosses the Earth, we observe a pulse
(c) the star undergoes periodic explosions of nuclear fusion that generate radio emission
(d) the star's orbiting companion periodically eclipses the radio waves emitted by the main pulsar
(e) a black hole near the star absorbs energy and re-emits it as radio waves
21. The strength of hydrogen absorption lines in the stellar spectra
(a) depends mostly on the abundance of Hydrogen in stars
(b) depends mostly on the core temperature of stars
(c) depends mostly on the surface temperature of stars
(d) can be used to determine ages of stars
(e) can be used to determine velocities of stars
22. If the orbit of a binary star system lies exactly in the plane of the sky, then we cannot measure
(a) orbital velocity of stars in binary
(b) temperatures of stars in binary
(c) chemical composition of stars in binary
(d) combined apparent luminosity of the stars in binary
(e) anything about these stars
23. A star has the same radius as the Sun but twice the Sun's surface temperature. This star must be _________ as luminous as the Sun.
(a) half (b) twice (c) four times (d) eight times (e) sixteen times
24. The two most abundant elements in stars are
(a) Nitrogen, Oxygen
(b) Iron, Hydrogen
(c) Carbon, Oxygen
(d) Helium, Oxygen
(e) Hydrogen, Helium
25. Which of the following is the best description of parallax?
(a) a change of radial velocity as a body moves past
(b) a reduction in gravity due to rotation
(c) a change in direction of a star as an observer changes position
(d) a distortion in the shape of a body due to the gravity of another body
(e) a change in star's radius as it pulsates
26. The Helium burning stage in the life of the Sun will be ________ than the Hydrogen burning stage because _________
(a) shorter; Helium is a less efficient fuel compared to Hydrogen
(b) longer; Helium is a less efficient fuel compared to Hydrogen
(c) same; the reason is unknown
(d) shorter; Hydrogen is a less efficient fuel compared to Helium
(e) longer; Hydrogen is a less efficient fuel compared to Helium
27. The correct order of Sun's outer layers (from surface outward) is
(a) corona, chromosphere, photosphere
(b) corona, photosphere, chromosphere
(c) photosphere, chromosphere, corona
(d) chromosphere, corona, photosphere
(e) photosphere, corona, chromosphere
28. Nuclear fusion reaction in the Sun's core
(a) transforms Hydrogen into Helium
(b) is such that the net mass of the products is somewhat less than the mass of the initial ingredients
(c) produces neutrinos
(d) is the source of Sun's energy
(e) all of the above
29. At the event horizon of a _________ the escape velocity is ________ the speed of light.
(a) main sequence star; equal to
(b) white dwarf; greater than
(c) neutron star; less than
(d) black hole; equal to
(e) X-ray binary; greater than
30. The most fundamental of a star's properties is its
(a) luminosity (b) temperature (c) radius (d) distance from the Sun (e) mass
NAME __________________________________ LAB # _________________________
Astronomy 1001 - Midterm #2 - April 4th Dr. Liliya Williams - Spring 2005
II. Short Answers (10 pts. each)
1. What defines a Main Sequence Star? How is it different from a Jupiter-type planet? How does the object's mass figure in distinguishing planets from stars?
2. Briefly describe two manifestations of the magnetic field activity in the Sun.
(over for #3)
NAME __________________________________ LAB # _________________________
Astronomy 1001 - Midterm #2 - April 4th Dr. Liliya Williams - Spring 2005
3. Give two examples of phenomena that involve special or general relativity. Briefly explain each one.
(over for #1 & #2)