MULTIPLE CHOICE QUESTIONS (50 pts.)Choose the BEST answer to each of the following questions using what you have learned in ASTR 101. Indicate your choice on the scantron. (2 pts. each)

1. Certain regions viewed with optical telescopes appear black, like the Horsehead Nebula in Orion. Why?

A. There are no stars here.B. Black holes limit our view.C. Dust in this region scatters visible photons out of our line of sight.D. The gas in the region absorbs all of the starlight.E. Some regions in space are completely empty.

2. The continuous spectrum (rainbow) that Mrs. Deming showed in class was produced by passing white light through a prism. The rainbow was produced as

A. different colored atoms passed through the prism and were knocked out.B. components of white light (colors) were refracted by different amounts by the prism.C. the energy was diverted and converted into visible light.D. the prism converted ultraviolet photons to visible photons.E. the prism converted infrared photons to visible photons.

3. Uranus and Neptune appear blue-green through a telescope becauseA. methane in their atmospheres absorbs mainly red photons.B. methane in their atmospheres absorbs mainly blue and green photons.C. their surfaces are covered with water and their clouds are very thin.D. both of them have very small masses compared to the Earth.E. the wind speeds are very high and produce a blue shift.

4. The single most important factor influencing a star’s evolution isA. the strength of its magnetic field.B. its rotation rate.C. its surface temperature.D. its mass.E. its diameter.

5. If there are five objects of the same size that have different temperatures, the hottest object would be the one emitting the greatest number of

A. radio photons.B. red photons.C. blue photons.D. ultraviolet photons.E. X-ray photons.

14. During the first three weeks in April we were noticing two planets very close together in the western sky about 40 minutes after sunset. Name them.

A. Venus and MarsB. Venus and MercuryC. Venus and SaturnD. Mars and SaturnE. Saturn and Jupiter

15. The oldest regions on the Martian surface as investigated during Lab #3 are those withA. fault features.B. volcanoes.C. channels.D. many impact craters.E. sand dunes.

16. Halley’s comet is named after Sir Edmund Halley because A. he was the first person to see it.B. he correctly calculated its orbital period.C. although he had nothing to do with the comet, he was famous at the time.D. Galileo discovered it and named it after his friend.E. he was the British Royal Astronomer when the comet first appeared.

17. The mass limit for a white dwarf star is 1.4 solar masses. Why?A. Above this mass the neutron pressure cannot balance gravity.B. Above this mass the electron pressure cannot balance gravity.C. Below this mass the star becomes a pulsar.D. Below this mass the star becomes a black hole.E. The star would become a supernova below this mass.

18. Sunspots appear are cooler than the surrounding photosphere becauseA. hot gas clouds in the upper atmosphere cast shadows onto the photosphere.B. magnetic fields inhibited the flow of energy rising to the photosphere from below.C. nuclear fusion has stopped in this part of the photosphere.D. large numbers of neutrinos are exiting the Sun in this region.E. this region has just produced a solar flare.

19. Between the orbits of which planets do most of the asteroids in the Solar System reside?A. Earth and MarsB. Mercury and VenusC. Mars and JupiterD. Neptune and PlutoE. Jupiter and Saturn

20. The mass of Jupiter was first calculatedA. from analysis of the motions of its moons.B. using its distance from the Sun and its rotational period.C. using its angular size and distance from Earth.D. using data from spacecraft flybys.E. by measuring the time that it takes for the Red Spot to disappear from view.

21. Today the Sun physically dips below the horizon at 7:52 PM EDT. However, it will remain visible for an additional 4 minutes. Why?

A. because we live at a northern latitudeB. due to atmospheric refractionC. due to atmospheric reflectionD. because in two years there will be a leap yearE. because the Sun is north of the Celestial Equator

22. If you know the value of (m – M) for a star, then you can determineA. the spectral class of the star.B. the star’s distance.C. the star’s diameter.D. the surface temperature of the star.E. the star’s mass.

23. In order to be classified as a planet in our Solar System, a body must orbit the Sun andA. be round.B. have at least one moon.C. clear its orbit of other objects.D. all of the above.E. only answers A and C.

24. A blue visible photon has ___________________________ a red visible photon.A. the same energy and wavelength asB. a longer wavelength and more energy thanC. a longer wavelength and less energy thanD. a shorter wavelength and more energy thanE. a shorter wavelength and less energy than

25. Ozone in the Earth’s stratosphereA. is the Earth’s most abundant atmospheric greenhouse gas.B. breaks down infrared radiation.C. absorbs much of the incoming solar ultraviolet radiation.D. forms when ordinary oxygen mixes with freon.E. has been building up as a result of industrial combustion.

SHORT ANSWER QUESTIONS (50 pts.) Using what you have learned in ASTR 101, answer the following questions as completely as you can.26. a) On the evening of May 5, the Eta Aquarid meteor shower will occur. Explain why a meteor shower like the Eta Aquarids occurs at a predicted time each year. (4 pts.)

b) Explain how an aurora is produced. (5 pts.)

EXTRA CREDIT Why does the gas tail of a comet always point away from the Sun. (2 pts.)

27. a) How do astronomers explain a pulsar’s variation in radio waves? Include a labeled sketch and be sure to explain how the radio waves are produced as well as why they appear to vary. (5 pts.)

b) Why is Io (Jupiter’s moon) volcanically active? Explain. (3 pts.)

c) You read in a magazine that an astronomer has determined that the bright star Sirius is approaching the Earth at a velocity of 8 km/sec. How was this information determined? (3 pts.)

29. a) Describe the process that is occurring now in the Sun to produce its energy and explain how the Sun’s stability is maintained against gravity. Be complete. (5 pts.)

b) Describe what will happen inside the Sun at the end of its main sequence lifetime and how this initiates physical changes as the Sun enters the next phase of its stellar evolution after the main sequence. (4 pts.)

30. a) It is theorized that Earth was struck by a sizeable asteroid or comet nucleus (at least 6 miles across) 65 million years ago. Describe how this event could produce the mass extinction that occurred at this time. (4 pts.)

b) Explain why the greenhouse effect occurs on the Earth. Include a labeled sketch with your explanation. (6 pts.)