ASTR 104 – Winter 2007 Intersession – Test 1 answers

(1) Which of the following statements about planets and stars is correct?
– Planets look smaller than stars when viewed through a telescope.
b. Planets move on the celestial sphere over time, stars basically don't.
– Stars twinkle because they burn, planets don't because they reflect light.
– Planets appear brighter in the sky than stars because they are closer to us.

(2) What is an arcminute?
– The distance a star covers in the sky in one minute.
– One minute of time, as measured with a solar clock.
c. A very small angle, equal to 1/60-th of a degree.
– The angle by which the Earth turns in one minute.

(3) What is the difference between a star of magnitude 1 and one of magnitude 5?
– That the first one is much smaller than the second one.
– That the first one is much larger than the second one.
– That the first one is much dimmer than the second one.
d. That the first one is much brighter than the second one.

(4) What is the meridian?
– The point directly overhead in the sky.
– The point on the celestial sphere where the Sun is on March 21st.
c. The line in the sky from North to South going through the Zenith.
– The path along which the Sun moves on the celestial sphere.

(5) What is right ascension?
– The maximum height along a planet's orbit, with respect to the ecliptic.
– The longitude of the point on the Earth where a telescope is located.
c. A coordinate on the celestial sphere that is a star's equivalent to longitude.
– The tilt angle between the Moon's orbit and the Earth's orbit.

(6) The latitude of Oxford is about 34° North. Does this tell us something about where Polaris is in the sky?
a. Yes, the altitude of Polaris is 34°.
– Yes, the azimuth (direction) of Polaris is 34°.
– Yes, Polaris is 34° above the celestial equator.
– No, because stars like Polaris move in the sky.

(7) When is a planet's motion called retrograde?
– When it rotates backward around its axis.
b. When it drifts Westward on the celestial sphere.
– When it moves away from us and looks smaller.
– When it rises in the West and sets in the East.

(8) Why did prehistoric astronomical sites have circular stone arrangements?
a. To mark directions where astronomical objects rise and set.
– To indicate places where stars could be seen without light pollution.
– To keep track of dates when eclipses were predicted to occur.
– To represent artistically the celestial sphere and the stars' positions.

(9) How can you approximately tell the time at night by looking at the Moon?
– The position of the Moon by itself tells you the time, because the Moon is always high at the same time.
– You can tell by looking at the color of the Moon, which changes throughout the day and night.
c. If you see what phase the Moon is in, you will know when it rises, when it is high up, and when it sets.
– The phase of the Moon changes throughout the day and night, and it tells you what time it is.

(10) What part of the world do we trace the earliest attempts to understand and make models of the Solar System to?
– Mexico and Central America.
b. Greece and the Middle East.
– Northern Europe.
– Southern Africa.

(11) Which ancient Chinese contributions to astronomy do we still use?
– Their stone circles built to track the Sun and stars.
b. The extensive records they kept of events in the sky.
– The theories they introduced for the motion of planets.
– Their mathematical tools and names for many stars and constellations.

(12) Around what time did Copernicus and Tycho Brahe live?
– The 5th century BC.
– The 2nd century AD.
c. The 1500's.
– The 1800's.

(13) How was Tycho Brahe able to establish that comets were more distant than the Moon?
– He measured the time it takes a comet to complete a full orbit.
b. He found the parallax of a comet as seen from different places on Earth.
– He measured the apparent size of a comet, as seen through a telescope.
– He applied Newton's laws and found the force of gravity felt by a comet.

(14) According to Kepler's laws, the orbit of a planet is:
– A circle, with the Sun at the center.
b. An ellipse, with the Sun at one of the foci.
– An ellipse, except during periods of retrograde motion.
– A circle, with epicycles added in to account for detailed observations.

(15) What did Galileo observe about the Sun with his telescope?
– That it does not revolve around the Earth.
b. That there are imperfections, dark spots on its surface.
– That it gets its energy from nuclear reactions.
– That it also has moons orbiting around it.

(16) Do dust particles in space feel a gravitational force pulling them towards each other?
a. Yes, all objects produce an attractive gravitational force.
– No, for gravity to act one object must be much bigger than the other one.
– No, gravity is a force that only stars and planets can produce.
– No, sometimes the force of gravity pushes them away from each other.

(17) What allowed Newton to add a few details that were not in Kepler's laws of planet motion?
– Newton had better data available on the positions of planets.
b. Newton made predictions based on general laws of motion and gravity.
– Newton realized that Kepler had made a few calculational errors.
– Newton knew what the planets and the Sun were made of.

(18) The positive particles in the core of an atom are the
– Electrons.
– Ions.
– Neutrons.
d. Protons.

(19) What force attracts protons and electrons and keeps them together to form atoms?
– Gravity.
b. The electric force.
– Inertia.
– The force of friction.

(20) Under which of the following circumstances do atoms become ions?
– When one or more neutrons are added to them.
– At temperatures so cold that all motion freezes inside them.
– After they have emitted a photon of light.
d. When they lose one or more electrons.

(21) What is a molecule?
– An atom that has lost one or more protons.
b. The smallest unit of a chemical substance, made up of two or more atoms.
– The smallest known unit of matter, obtained by splitting an atom.
– An atoms that has captured one or more photons.

(22) When heat is transferred to an object, what kind of energy are we adding to it?
– Kinetic energy.
b. Thermal energy.
– Potential energy.
– Mass energy.

(23) What is the lowest possible temperature that can be reached?
a. 0 Kelvin.
– 0 degrees Celsius.
– 0 degrees Fahrenheit.
– There is no minimum, the temperature can always be decreased.

(24) What is the wavelength of a wave?
– The distance the wave travels in one second.
b. The distance between two crests of the wave.
– The distance between the beginning and the end of the wave.
– The distance between the wave source and the observer.

(25) If two light waves have different wavelengths, must they have also different frequencies?
– No, all forms of light have the same frequency.
– Not necessarily, the frequency depends also on other factors.
– Yes, the one with the longer wavelength has a higher frequency.
d. Yes, the one with the longer wavelength has a lower frequency.

(26) What is diffraction?
– The bending of light when it passes near a very massive object.
b. The spreading of light around edges, such as when it goes through a hole or slit.
– The blurring of an image when light traverses the atmosphere.
– The bending of light crossing the boundary between different transparent materials.

(27) Why does light produce diffraction?
a. Because it is made of waves.
– Because it is made of particles.
– Because it contains different colors.
– Because of the composition of the Earth's atmosphere.

(28) Which of these types of waves is different in nature from the others?
– X-rays.
– Microwaves.
c. Sound.
– Visible light.

(29) What does the Doppler shift of an object tell us about it?
– The mass of that object.
– The temperature of that object.
– The types of atoms that the object is made of.
d. The speed at which it is moving towards or away from us.

(30) What is a continuous spectrum?
a. One containing light of all wavelengths or colors.
– One coming from a source that emits light all the time.
– One prioduced by a moving object.
– One made from a long-time exposure with the camera.

(31) From which of the following would you receive light with an absorption line spectrum?
– Hot thin gases.
– Hot solids or very dense fluids.
– Any strongly absorbing solid material.
d. Cool gases placed between a source that emits a continuous spectrum and us.

(32) What kind of spectrum does a regular light bulb with a hot filament produce?
– An emission line spectrum.
– An absorption line spectrum.
c. A continuous emission spectrum.
– A continuous absorption spectrum.

(33) What kind of spectrum do we get from a star like the Sun?
– An emission line spectrum.
b. An absorption line spectrum.
– A continuous emission spectrum.
– A continuous absorption spectrum.

(34) Around what year were telescopes first used in astronomy?
– 3000 BC.
– 300 BC.
c. The early 1600's.
– Around 1920.

(35) What feature has made 10-m or larger mirrors for optical telescopes possible?
– A new type of glass made it possible to build thinner mirrors.
b. The larger mirrors are made of different pieces, which are connected together.
– Advances in laser techniques have enabled us to polish surfaces much better.
– Better supports are now able to support the weight of larger mirrors.

(36) What is the main reason the Hubble Telescope gives great images?
a. It is outside the Earth's atmosphere.
– It has the largest mirror ever built.
– It is closer to the stars than Earth-bound telescopes.
– It has the most sophisticated instruments currently in use.

(37) What are the direct consequences of increasing the size of a telescope mirror?
a. Ability to see fainter objects and better angular resolution.
– Ability to see fainter objects and greater image magnification.
– Better angular resolution and greater image magnification.
– Greater image magnification and ability to see a larger portion of the sky.

(38) Which of these statements about radio telescopes is correct?
a. They have to be very large because radio waves have long wavelengths.
– They are shaped like straight antennas rather than round dishes.
– They can only operate during the daytime, not at night.
– They must be located outside the Earth's atmosphere.

(39) Why are some infrared telescopes used on airplanes or in space?
– Because on the ground they would be too affected by vibrations.
b. Because IR radiation is absorbed to a large extent by the atmosphere.
– Because objects emitting IR radiation are further away in space.
– Because on the ground there is too much light pollution.

(40) What are gravitational waves?
– Sound waves that reach Earth from outer space, produced by very massive stars.
– Seismic vibrations of the ground on Earth, that affect the performance of telescopes.
– Turbulent fluctuations in the Earth's atmosphere that blur astronomical images.
d. Ripples in the fabric of space-time predicted by Einstein's theory of relativity.