If Earth's rotation were such that it completed exactly one rotation in 18 hours, how long would one day (sunrise to sunrise) be? 

18 hours

When we look at an object that is two billion light-years away, we see it...

as it was two billion years ago.

Due to engine troubles, the starship Enterprise can only go 1/10 of the speed of light. How long will it take them to reach the nearest star (about 4 light-years in distance)? 

40 years 

You are standing on the north pole. Which way is Polaris, the North Star? 

 directly overhead 

Suppose it is a full moon, as seen from the Earth. How would the Earth appear to an astronaut who was visiting the moon at that time? 

The side of the Earth facing the Moon is completely dark. 

Why is it cold in Michigan in the winter? 

The tilt of the Earth's axis means that Michigan receives less direct sunlight then. 

Like Earth, Mars rotates about its axis every 24 hours, and its axis is also inclined by about 23 degrees. Mars takes about 680 Earth days, however, to orbit the Sun. If humans establish a base on Mars, about how long in Martian days will their summer (summer solstice to fall equinox) be?

170 days 

Where on Earth can you see the sun pass directly overhead during the day and see Polaris very high in the sky at night? 

There is no such location 

In what direction will the sun rise the week of Halloween? 

south of due east 

On what day of the year does Sparty cast no shadow at noon? 

There is no such day

Why are astronauts weightless in the Space Station? 

because the Space Station is constantly in free-fall around the earth 

You are standing on a scale in an elevator. Suddenly you notice that your weight increases. From this you conclude that 

The elevator is accelerating upwards. 

Suppose you drop a 10-kg ball and a 1-kg ball on the moon from the same height and at the same time. What will happen? 

Both balls will hit the ground at the same time 

How would the gravitational force between the earth and moon change if the moon were moved 2 times farther away?

Hint: Recall that the force can be expressed as

Force = G x (mass₁ x mass₂)/(distance²)

The force becomes 4 times weaker. 

When Copernicus first created his Sun-centered model of the universe, it did not lead to substantially better predictions of planetary positions than the Ptolemaic model. Why not? 

Copernicus used perfect circles for the orbits of the planets. 

Why did Ptolomy have the planets moving on epicycles (wheels upon wheels) in his model of the universe?

To account for the occasional apparent retrograde motion of the planets 

When we see Venus in its nearly full phase, what phase would the Earth be for an observer on Venus? (Hint: draw and label a diagram of the relative positions of the Sun, Venus, and the Earth that are required to see Venus in its full phase.) 

nearly full

In which of the following situations are you not accelerating? 

Going at 100 kilometers per hour in a straight line 

Suppose the Sun shrank in size but its mass remained the same. What would happen to the Earth's orbit?

Earth's orbit would be unaffected. 

Conservation of angular momentum dictates that the orbital speed of a planet 

 is faster when it is closer to the Sun and slower when it is farther away. 

How does the gravitational force exerted by the Moon on the Earth compare to that exerted by the Earth on the Moon? 

It is the same. 

When an asteroid approaches the moon, that asteroid has gravitational potential energy. What happens to that potential energy when the asteroid impacts the moon? 

 It is converted into heat. 

The surface gravity on the Moon is about 1/6 that of Earth. What is the mass of a 72 kg person on the Moon? 

72 kg 

The mass of Jupiter can be calculated by measuring... 

...the orbital period of one of Jupiter's moons and the distance between Jupiter and that moon. 

Which of the following lists the categories of electromagnetic radiation from shortest wavelength to longest wavelength? 

gamma ray, X-ray, ultraviolet, visible, infrared, radio 

We can see each other in the classroom right now because we 

reflect visible light.

What causes stars to twinkle? 

Moving gases in Earth's atmosphere randomly bend light rays from stars. 

Hydrogen has an absorption line with wavelength 121.6 nm. Suppose you find this line in the spectrum of a star, but with a wavelength of 116.2 nm. From this you conclude that 

the star is moving towards us.

 Put the following in order from smallest to largest.

distance to Neptune, one light-month, distance to nearest star, distance to center of Milky Way 

What information is likely to be the most useful for determining the chemical composition of a distant star?

The wavelengths of the absorption lines in its spectrum 

Which of the following conditions must exist for a solar eclipse to occur? 

Moon phase is new, and the Moon is passing through the Earth's orbital plane.

About how many stars are there in the disk of our Milky Way galaxy?

100 billion 

Let's assume you could drive a car in space. About how long would it take to drive from the Earth to the Sun?

200 years 

Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color? 

Its surface is cooler than the surface of the Sun. 

You observe a full moon rising at sunset. What will you see 6 hours later? 

a full moon on or near your meridian 

Why is it summer in the Northern Hemisphere when it is winter in the Southern Hemisphere? 

The Northern Hemisphere is tilted toward the Sun and receives more direct sunlight. 

At approximately what time would a first quarter moon rise? 

noon 

Which of the following is smallest?

size of a typical planet 

Why is the daytime sky blue? 

Air molecules scatter blue light more easily than red light.

To achieve an angular resolution of 1 arcsecond at a wavelength of 400 nanometers, an optical telescope needs to have a diameter of 10 centimeters. What diameter would a radio telescope need to have to reach the same resolution, but at a wavelength of 4 centimeters?

10 kilometers 

You are somewhere in the solar system. The surface is hot as coals and heavily cratered. Although the sun is extremely bright, the sky is black and you can see stars. Where are you? 

Mercury 

You are somewhere in the solar system. It is extremely cold, and the sun looks like a small dot of light, compared to how it looks from Earth. You are standing on an icy surface, and an icy moon looms in the sky. Where are you? 

Pluto 

You are somewhere in the solar system. Although you are standing on a rocky surface, gravity is extremely weak. There is no atmosphere, and the object you are standing on is about the size of a city. Where are you?

Asteroid 

You are somewhere in the solar system. Nearby is an active volcano, and the surface around you is coated with a frost of sulfur dioxide. Jupiter looms in the sky overhead. Where are you? 

Io 

You are somewhere in the solar system. The atmosphere is hazy, and is composed of nitrogen, methane, and ethane. The temperature is cold, (-180 degrees C), you are standing on an icy surface, and there is a nearby lake of what appears to be liquid methane. Where are you? 

Titan 

Why do Uranus and Neptune appear blue? 

Their atmospheric methane absorbs red and reflects blue light 

You analyze a rock that contains small amounts of potassium-40 (half-life: 1.25 billion years) and argon-40. There is three times as much argon-40 as potassium-40. How old is the rock? 

2.5 billion years 

Analysis of which of these rocks would give the oldest age? 

Samples from meteorites 

How does the Earth's Moon compare with other moons?

It is much larger than other moons relative to the size of the planet it orbits. 

According to radioactive dating of meteorites, approximately how old is the solar system? 

4.6 billion (4.6×10⁹) years 

Which of the following lists the ingredients of the solar nebula, from most abundant to least abundant? 

light gases (H, He), hydrogen compounds (H₂O, CH₄, NH₃), rocks and metals 

What is the leading scenario for the formation of the Moon?

It formed from the material ejected during a giant impact on the young Earth. 

According to our present theory of the formation of the Solar System, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system?

Ice, metal, and rock could all condense in the outer solar system, while only metal and rock could condense in the inner solar system. 

What is the main disadvantage of the transit method for finding extrasolar planets?

One can only find planets in edge-on orbits. 

How do astronomers think that the "hot Jupiters" around other stars were formed? 

They formed as gas giants beyond the frost line and then migrated inwards. 

What is the main evidence that an asteroid or comet impact led to the mass extinction of dinosaurs?

A thin layer of the rare element iridium found in rocks around the world, dated to about 65 million years ago. 

You are looking for extrasolar planets using the Doppler technique. What features are most important for you to measure? 

The wavelengths of lines in the spectrum. 

What type of extrasolar planet is most easily detected by measuring the star's Doppler shift? 

Jupiter-sized planets with short orbital periods 

Which of the following has the hottest surface temperature? 

 Venus 

Which of the following show evidence for ancient river beds?

Mars

 Which of the following properties is common to all the greenhouse gases? 

Absorb infrared light 

Earth's atmosphere contains only small amounts of carbon dioxide because 

carbon dioxide dissolves in water, and most of it is now contained in the oceans and carbonate rocks. 

Why does Venus have such a great difference in temperature between its "no atmosphere" temperature and its actual temperature? 

It has a large amount of carbon dioxide in its atmosphere. 

What would happen to Earth's temperature if you covered the entire surface of the Earth with (white) ice?

Its average temperature would go down.

Which of the following is not strongly heated by tides? 

the Moon 

Which of the following best describes the origin of ocean tides on Earth? 

Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the Earth. 

Why didn't a planet form where the asteroid belt is now located? 

Gravitational tugs from Jupiter prevented material from collecting together to form a planet. 

How often, on average, is the Earth struck by an asteroid or comet large enough to cause mass extinctions?

once every 100 million years 

Assume an asteroid about 100 meters in size hits the Moon directly. About how large across is the resulting crater?

1 kilometer 

 What is the main reason that we observe few large craters on the surface of the Earth, compared to other terrestrial planets?

Craters on Earth have been erased by weathering and tectonic activity. 

How often, on average, do boulder-sized (1 meter) objects enter the Earth's atmosphere? 

once a day 

What percentage of the mass of the solar nebula consisted of elements other than hydrogen and helium? 

2 % 

What is the main difference between the human-caused rise in carbon dioxide levels over the last 200 years and other episodes of climate change in Earth's history?

The recent human-caused rise is much faster than other episodes of climate change. 

I am tending bar and offer you the choice of two different kinds of whiskey. One is radioactive and one is not. Which one is legal for me to sell you, assuming you are of age?

Radioactive whiskey 

What is the most massive body in the Solar System that is not classified as a planet or moon?

Eris 

There are several reasons that Venus is hotter than Earth. Which of the following reasons is unimportant?

The total amount of carbon on Venus. 

Suppose that Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be:

About 60 degrees F cooler: well below the freezing point of water.     

According to the leading theory of Solar System formation, why do all the planets orbit the Sun in the same direction and in nearly the same plane?

Conservation of angular momentum ensures that any rotating, collapsing cloud will end up as a spinning disk. 

How does the Sun produce the energy that heats our planet? 

Hydrogen nuclei are fused into helium nuclei, producing energy 

About how long does a star like the Sun live on the main sequence? 

10¹⁰ (ten billion) years 

Why doesn't fusion occur in the Sun's corona, even though it is approximately the same temperature as the Sun's core?

The density in the corona is too low 

If fusion in the core of a main sequence star were to suddenly (over a short time scale) speed up and release more energy, what would happen? 

The core would expand and cool down 

A star's luminosity is the 

total amount of light that the star radiates each second. 

If the Pleiades cluster was 2 times farther away, its stars would appear to be 

1/4 as bright 

Which one property of a star will determine all other characteristics of that star over the course of its lifetime?

Mass 

Which statement is the most correct in comparing a spectral type G main sequence star to a spectral type O main sequence star? 

The G star is dimmer, cooler, smaller, and will live longer than the O main sequence star. 

Consider a star of mass 2 M_sun that has a luminosity 16 times greater than the Sun. How does its main-sequence lifetime compare to that of the Sun? 

8 times less 

What properties do stars belonging to the same cluster have in common? 

B and C 

Use the following Hertzsprung-Russell diagrams of four hypothetical clusters to answer the next question.

Which star cluster is the oldest?

Where were the elements, other than hydrogen and helium, in the solar system produced? 

In the interior of stars 

What property is common to all main sequence stars? 

All are fusing hydrogen into helium 

Approximately what fraction of a star's lifetime is spent on the main sequence? 

90% 

What happens immediately after hydrogen is used up in the core of a star?

The star contracts and heats up 

 Why does helium fusion require higher temperatures than hydrogen fusion? 

Helium nuclei have a larger charge than hydrogen nuclei, and repel each other more strongly 

Do stars with iron fusion occurring in their cores exist? 

No, iron fusion does not release heat 

What is the fate of a main-sequence star that has 20 times the Sun's mass? 

It will explode and leave behind either a neutron star or black hole. 

Which of the following represents evidence for the formation of heavy elements (via nuclear fusion) in stars?

The lower concentrations of heavy elements in old main sequence stars 
The higher abundance of elements with even numbers of protons in the Universe 
The lifetimes of stars 
The large enrichments of heavy elements in giant stars, planetary nebulae, and supernova remnants 

All of the above 

For a white dwarf to become a nova, it is necessary for it to

be in a binary system 

Which of the following stars will become a white dwarf the soonest? (Assume that main sequence stars are at the midpoint of that evolutionary stage, i.e., that they have fused half of the hydrogen in their cores to helium.)

A one solar mass red giant star 

How will the Sun die? 

In a planetary nebula explosion, leaving behind a white dwarf 

Which of the following is most likely to produce a white-dwarf supernova? 

a binary consisting of a white dwarf and a red giant star 

Black holes are formed by 

Supernovae from the most massive stars 

Suppose our Sun were to collapse to a black hole. How would the Earth be affected? 

The Earth's orbit would be unchanged. 

Some X-ray binaries are candidates for black holes because 

The object in the center of the accretion disk is too massive to be a neutron star 

What is a black hole? 

A collapsed object with such strong gravity that not even light can escape it. 

What is a nova? 

The explosion of an accreted layer of hydrogen and helium on a white dwarf. 

How were neutron stars discovered? 

By accident, when radio pulsations were detected from one. 

Stars with different spectral types show different absorption lines. This is because 

The stars have different temperatures.

Suppose a cluster of stars with masses from 0.1 to 30 M_sun was formed. How would this cluster look 100 million years later? 

All of the bright blue stars would be gone. 

Consider the information given below about three main sequence stars. 

Star A will be a main sequence star for 3 billion years total. 
Star B has the same luminosity as the Sun. 
Star C has a spectral type of M. 

Which star has the greatest mass?

Star A 

Why is gravitational contraction not a workable explanation for the luminosity of the Sun?

Gravitational contraction cannot supply enough luminosity over the Sun's main sequence lifetime 

The energy from sunlight hitting the Earth today was produced in the core of the Sun about how long ago?

10,000 years 

What is the fundamental difference between the energy production by the Sun and nuclear power plants on Earth?

The Sun uses fusion to produce energy, while power plants use fission 

You want to produce the output of a 10 Megawatt (10^7 Watts) power plant using solar panels. Assuming the panels have 100% efficiency and the flux of solar radiation is 1000 Watts/square meter, what approximate area needs to be covered with solar panels?

A football field 

Which of the following classes of star is the most numerous in the Galaxy?

low-mass main sequence stars 

Consider the iron found in our blood. Where was most of it formed?

About half was formed in white dwarf supernovae and half in massive star supernovae

What happens when a white dwarf exceeds the maximum mass allowed by degeneracy ('chair') pressure?

It goes supernova 

Assume that Earth-like planets have the same chance of forming around any star, and that we can detect all such planets with the same efficiency. If so, the first Earth-like planet outside the Solar System is likely to be found around what kind of star?

A main sequence M star