Final Exam Review

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Final Exam Review

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

The theory that astronomers have developed to describe the formation of the universe is called the

a.	expanding cloud theory.
b.	time warp theory.
c.	galactic expansion theory.
d.	big bang theory.

Earth is unique among the planets because of

a.	its rocky surface.
b.	its oceans.
c.	its large size.
d.	the direction in which it rotates.

In the Southern Hemisphere, the summer solstice occurs when the sun is directly overhead at

a.	the equator.
b.	23.5° south latitude.
c.	23.5° north latitude.
d.	30° south latitude.

Photographs of the far side of the moon show that

a.	the far side is much rougher than the near side.
b.	there is water on the far side.
c.	the far side has active volcanoes.
d.	the far side has a smooth surface.

The tendency of a moving object to continue moving in a straight line or a stationary object to remain in place is called

a.	orbital speed.
b.	mass.
c.	inertia.
d.	gravity.

Galileo saw that much of the moon’s surface is covered with round pits called

a.	highlands.
b.	seas.
c.	craters.
d.	maria.

Day and night are caused by

a.	the tilt of Earth’s axis.
b.	Earth’s revolution around the sun.
c.	eclipses.
d.	Earth’s rotation on its axis.

A star is born when

a.	a nebula expands.
b.	helium and oxygen combine.
c.	nuclear fusion starts.
d.	a protostar begins to cool.

Both reflecting and refracting telescopes are designed to

a.	break visible light into colors of the spectrum.
b.	separate visible light from ultraviolet and radio waves.
c.	gather and focus visible light.
d.	work better with short-wavelength radiation.

10.

Because the moon rotates once for each revolution around Earth,

a.	you see some phases more than others.
b.	a different side of the moon faces Earth each day.
c.	you never see the far side of the moon.
d.	the far side of the moon is visible only during the full moon phase.

11.

You are more likely to see a solar eclipse than a lunar eclipse because

a.	the moon’s shadow covers all of Earth during a solar eclipse.
b.	new moon phases occur less often than full moon phases.
c.	only people on the daytime side of Earth can see a solar eclipse.
d.	you must be in the moon’s shadow to see a solar eclipse.

12.

How large is the moon compared to Earth?

a.	about the same diameter as Earth
b.	about one half the diameter of Earth
c.	about one fourth the diameter of Earth
d.	about one eighth the diameter of Earth

13.

When the north end of Earth’s axis is tilted toward the sun, North America will experience

a.	more indirect rays and shorter days.
b.	more indirect rays and longer days.
c.	more direct rays and shorter days.
d.	more direct rays and longer days.

14.

The hypothesis that Mars may once have had the conditions needed to support life is based on

a.	its similar size to Earth.
b.	its reddish surface.
c.	surface patterns that look like dried stream beds.
d.	the system of canals seen by Schiaparelli.

15.

The force that tends to pull together the matter in stars is

a.	gravity.
b.	nuclear fusion.
c.	expansion.
d.	nuclear fission.

16.

When the solar system formed, the spheres that lost most of their gases became the

a.	inner planets.
b.	comets.
c.	outer planets.
d.	asteroids.

17.

When are tides highest?

a.	during the moon’s first quarter phase
b.	when the sun, Earth, and the moon are nearly in a line
c.	during the moon’s third quarter phase
d.	when the moon is at a right angle to the sun

18.

The Milky Way Galaxy is a type of

a.	spiral galaxy.
b.	cloud galaxy.
c.	elliptical galaxy.
d.	irregular galaxy.

19.

The model in which Earth is at the center of the system of planets is called the

a.	solar system.
b.	heliocentric system.
c.	geocentric system.
d.	Copernican system.

20.

One of the main uses of satellites is

a.	launching deep-space expeditions.
b.	controlling the weather.
c.	photographing Earth’s surface.
d.	preventing ozone depletion.

21.

The solar wind is a stream of electrically charged particles produced by the sun’s

a.	chromosphere.
b.	photosphere.
c.	corona.
d.	core.

22.

For a solar eclipse to occur,

a.	the sun must be directly between Earth and the moon.
b.	the moon must be directly between Earth and the sun.
c.	the moon must be directly behind Earth.
d.	Earth must be directly between the sun and the moon.

23.

The asteroid belt is located

a.	between Earth and Mars.
b.	between Mars and Jupiter.
c.	between Jupiter and Saturn.
d.	between Saturn and Uranus.

24.

Reflecting telescopes differ from refracting telescopes in having

a.	no eyepiece lens.
b.	two large objective lenses.
c.	a mirror instead of an objective lens.
d.	one large objective lens.

25.

When compared to the gases around them on the sun, sunspots are

a.	hotter.
b.	the same temperature.
c.	cooler.
d.	brighter.

26.

Geosynchronous satellites above the equator

a.	revolve around Earth faster than other satellites.
b.	vary considerably in their distance from Earth.
c.	stay above the same point on Earth.
d.	follow an elliptical orbit.

27.

An equinox occurs when

a.	neither end of Earth’s axis is tilted toward or away from the sun.
b.	the north end of Earth’s axis is tilted away from the sun.
c.	the north end of Earth’s axis is tilted toward the sun.
d.	Earth’s axis is parallel to the sun’s rays.

28.

The atmospheres of the gas giant planets cannot escape into space because

a.	the gases are too heavy.
b.	the gases solidify at higher elevations.
c.	the planets have very strong gravities.
d.	although they are big, the planets have little mass.

29.

From new moon phase to full moon phase you see

a.	an increasing amount of the lighted side of the moon.
b.	a decreasing amount of the lighted side of the moon.
c.	the same amount of the lighted side of the moon.
d.	more of the lighted side, then less of the lighted side of the moon.

30.

The solar system formed from

a.	an expanding galaxy.
b.	a giant cloud of gas and dust.
c.	an enormous explosion.
d.	a black hole.

31.

Uranus is different from most other planets because it

a.	is the farthest from the sun.
b.	is mostly nitrogen and helium.
c.	rotates on its side.
d.	has the most moons.

32.

One indication that a planet may exist near another star is that

a.	the star varies in temperature.
b.	the star has a very slight back and forth motion.
c.	the star has very strong gravity.
d.	radio wave activity increases near the star.

33.

Tides are caused mainly by

a.	Earth’s rotation on its axis, which causes water to move.
b.	differences in how much the sun pulls on different parts of Earth.
c.	strong winds blowing water onto coasts.
d.	differences in how much the moon pulls on different parts of Earth.

34.

The phase of the moon you see depends on

a.	where you are on Earth’s surface.
b.	how much of the sunlit side of the moon faces Earth.
c.	how much of the moon’s surface is lit by the sun.
d.	whether or not an eclipse is occurring.

35.

Rocket propulsion is based on

a.	having a streamlined nose cone.
b.	having a three-stage booster system.
c.	hot gas being propelled out of the rocket.
d.	reducing friction as much as possible.

36.

Parallax is a method used to determine a star’s

a.	distance from Earth.
b.	temperature.
c.	composition.
d.	brightness

37.

There is enough fuel remaining in the sun to last for another

a.	1 billion years.
b.	5 billion years.
c.	10 billion years.
d.	15 billion years.

38.

When a meteoroid enters Earth’s atmosphere, it produces a streak of light called a

a.	meteor.
b.	asteroid.
c.	meteorite.
d.	comet.

39.

A supernova is the explosion of a dying

a.	medium-sized star.
b.	giant or supergiant star.
c.	protostar.
d.	nebula.

40.

Depending on its mass, a star may live from

a.	1 million to 10 million years.
b.	5 million to 100 million years.
c.	10 million to 200 billion years.
d.	10 billion to 500 billion years.

41.

Stars are classified according to their

a.	distance, size, and color.
b.	size, distance, and brightness.
c.	color, brightness, and temperature.
d.	size, brightness, and temperature.

42.

Conditions required for life on Earth include

a.	alternating day and night cycles.
b.	extreme differences in elevation.
c.	polar ice caps.
d.	liquid water.

43.

Meteoroids usually come from

a.	debris from other planets.
b.	solar winds.
c.	beyond the solar system.
d.	comets or asteroids.

44.

The chemical composition of a star can be determined using a(n)

a.	refracting telescope.
b.	spectrograph.
c.	satellite.
d.	reflecting telescope.

45.

What do all of the inner planets have in common?

a.	They have the same period of revolution.
b.	They have the same period of rotation.
c.	They have the same diameter.
d.	They are small and have rocky surfaces.

46.

Scientists think the moon was formed when

a.	a large object struck Earth, and material from both bodies combined.
b.	gravitational forces attracted materials from outer space.
c.	meteoroids collected and solidified within the pull of Earth’s gravity.
d.	gases from Earth escaped from the atmosphere and condensed.

47.

The Hertzsprung-Russell diagram shows that main sequence stars

a.	are mostly hot and dim.
b.	are mostly cool and bright.
c.	increase in brightness as they increase in temperature.
d.	decrease in brightness as they increase in temperature.

48.

Copernicus explained that

a.	the sun is at the center of the system of planets.
b.	the sun and the planets revolve around Earth.
c.	the geocentric system is correct.
d.	there are only six planets.

49.

The heliocentric system gained support when Galileo observed that

a.	one side of the moon always faces Earth.
b.	most of the smaller planets are closer to the sun.
c.	Venus goes through phases similar to those of Earth’s moon.
d.	the orbit of each planet is an ellipse.

50.

Solar prominences

a.	are cooler than the rest of the chromosphere.
b.	link different parts of sunspot regions together.
c.	cannot be seen during an eclipse.
d.	are hotter than the rest of the chromosphere.

51.

When stars begin to run out of fuel, they first become

a.	red giants or supergiants.
b.	supernovas.
c.	white dwarfs.
d.	neutron stars.

52.

A range of colors formed when white light passes through a prism is called a

a.	lens.
b.	photograph.
c.	spectrum.
d.	ray.

53.

The sun produces energy by

a.	attracting it with the force of gravity.
b.	nuclear fission.
c.	burning fuels such as oil.
d.	nuclear fusion.

54.

It’s a basic law of physics that for every force, or action, there is

a.	a decreased force, or reaction.
b.	an equal force in the same direction.
c.	an increased force, or reaction.
d.	an equal and opposite force, or reaction.

55.

Much of what scientists know about the moon has come from

a.	revolving around the moon.
b.	studying the moon through telescopes.
c.	astronauts walking on the moon.
d.	studying moon rocks gathered by astronauts.

56.

What shape are the orbits of most comets?

a.	long, narrow ellipses
b.	circles
c.	nearly circular ellipses
d.	spherical

57.

The lifetime of a star depends on its

a.	temperature.
b.	brightness.
c.	mass.
d.	magnitude.

58.

More than half of all stars are members of groups of two or more stars called

a.	galaxies.
b.	eclipsing binaries.
c.	star systems.
d.	star clusters.

59.

The electromagnetic spectrum is

a.	all of the colors of light you can see with your eyes.
b.	all of the different types of electromagnetic waves.
c.	a band of colors formed when white light passes through a prism.
d.	the distance between the crest of one wave and the crest of the next wave.

60.

During what phase can a lunar eclipse occur?

a.	new moon
b.	first quarter
c.	waxing gibbous
d.	full moon

61.

Earth has seasons because

a.	Earth rotates on its axis.
b.	the distance between Earth and the sun changes.
c.	Earth’s axis is tilted as it moves around the sun.
d.	the temperature of the sun changes.

62.

Galileo thought that the dark, flat parts of the moon’s surface were

a.	oceans.
b.	deserts.
c.	mountains.
d.	craters.

63.

Some astronomers think Pluto should not be called a planet because it

a.	is too far away.
b.	has such a large moon.
c.	is so small.
d.	cannot be seen without a telescope.

64.

One piece of evidence that supports the big bang theory is the observation that most galaxies are moving

a.	toward our galaxy.
b.	toward each other.
c.	in random directions.
d.	away from each other.

65.

Earth’s rotation takes about

a.	365 days.
b.	6 months.
c.	24 hours.
d.	1 month.

66.

Spectrographs help astronomers determine the

a.	position of a star in the sky.
b.	temperature of a star.
c.	distance to a star.
d.	diameter of a star.

67.

A light-year is

a.	365 days.
b.	the distance light travels in a year.
c.	the distance from Earth to Proxima Centauri.
d.	the amount of light the sun produces in a year.

68.

One complete revolution of Earth around the sun takes about

a.	one rotation.
b.	one season.
c.	one year.
d.	one eclipse.

69.

What color are the hottest stars?

a.	blue-white
b.	yellow
c.	red
d.	orange

70.

The brightness of a star depends on its

a.	distance and temperature.
b.	size and temperature.
c.	color and temperature.
d.	distance and color.

71.

Venus and Earth are much alike in terms of

a.	their size and density.
b.	their rates of rotation.
c.	their atmospheres.
d.	their direction of rotation.

72.

Scientists think that our universe is approximately

a.	1 to 5 million years old.
b.	1 to 2 billion years old.
c.	10 to 15 billion years old.
d.	100 to 200 billion years old.

73.

The amount of the lighted side of the moon you can see is the same during

a.	new moon and full moon phase.
b.	new moon and first quarter phase.
c.	first quarter and third quarter phase.
d.	full moon and third quarter phase.

74.

Instruments left on the moon to measure heat flow show that

a.	the center of the moon is molten.
b.	most of the moon’s interior is very hot.
c.	the moon’s interior has cooled almost completely.
d.	the moon has high seismic activity.

75.

Scientists have discovered that life forms on Earth exist

a.	in a very narrow range of conditions.
b.	in a very wide range of conditions.
c.	only in moderate temperatures.
d.	in moist or humid habitats only.

76.

What do the first four outer planets have in common?

a.	They are much larger than Earth and are made mainly of gases.
b.	They are about the same size as Earth and are made mainly of gases.
c.	They are much larger than Earth and are solid.
d.	They are about the same size as Earth and are solid.

77.

The two factors that combine to keep the planets in orbit are

a.	gravity and orbital speed.
b.	orbital speed and mass.
c.	mass and inertia.
d.	gravity and inertia.

78.

What solar feature can increase the solar wind, sometimes causing electrical power problems on Earth?

a.	prominences
b.	sunspots
c.	core emissions
d.	solar flares

79.

Europa is considered a good place to look for life because

a.	there may be liquid water under its icy crust.
b.	its equator has tropical temperatures.
c.	volcanic activity keeps it warm.
d.	it is the same size as Earth.

80.

Aside from Earth, which inner planet once had water on its surface?

a.	Mercury
b.	Europa
c.	Venus
d.	Mars

81.

All stars begin their lives as parts of

a.	nebulas.
b.	protostars.
c.	pulsars.
d.	double stars.

82.

Eclipsing binary stars can sometimes be identified because

a.	they are brighter than any single stars.
b.	they are all white dwarfs.
c.	they become dimmer at regular intervals.
d.	they are cool red stars.

83.

What layer are you looking at when you look at a photograph of the sun?

a.	photosphere
b.	chromosphere
c.	corona
d.	prominence

84.

When do neap tides occur?

a.	at new moon
b.	when the sun’s pull is in the same direction as the moon’s
c.	when the sun’s pull is at right angles to the moon’s
d.	at full moon

85.

Pluto is different from the other outer planets because it

a.	is almost entirely made of gases.
b.	is much larger than the others.
c.	has the most moons.
d.	is small and has a solid surface.

86.

How are elliptical galaxies and spiral galaxies different?

a.	Elliptical galaxies have almost no gas or dust.
b.	Elliptical galaxies vary more in shape than spiral galaxies.
c.	Spiral galaxies have almost no gas or dust.
d.	Spiral galaxies contain only old stars.

87.

Saturn’s rings are made up mostly of

a.	nitrogen and helium.
b.	ice and water vapor.
c.	volcanic dust particles.
d.	chunks of ice and rock.

88.

One major use of space stations is

a.	to launch trips to the moon.
b.	to obtain better photographs of Earth.
c.	to conduct scientific research.
d.	to monitor the activities of other satellites.

89.

Black holes form from stars that

a.	collapse extremely fast.
b.	lose all their gravitational attraction.
c.	were more than 40 times the mass of the sun.
d.	had first turned into white dwarfs.

90.

Putting rockets into space was made possible by the development of

a.	gunpowder fuels.
b.	taller single-stage rockets.
c.	smaller single-stage rockets.
d.	multistage rockets.

Completion

Complete each sentence or statement.

91.

Earth rotates on its axis about once every ____________________ hours.

92.

What happens to the universe in the future depends on the total force of gravity pulling the galaxies together, which depends on the total ____________________ of the universe.

93.

By studying moon rocks, scientists learned that ____________________ had struck the surface.

94.

A meteoroid that hits Earth’s surface is called a ____________________.

95.

A satellite that revolves around Earth at the same rate that Earth rotates is in a ____________________ orbit.

96.

The darkest part of the moon’s shadow is called the ____________________.

97.

The sun’s ____________________, which looks like a halo, can usually be seen only during a solar eclipse.

98.

All stars begin as part of a large amount of gas and dust called a(n) ____________________.

99.

If life were found on other worlds, it would be called ____________________.

100.

Galileo called the dark, flat parts of the moon ____________________ because they looked like seas.

101.

The brightness a star would have if it were at a specific distance from Earth is the star’s ____________________.

102.

Magnetic storms are a result of an increase in solar wind caused by explosions called ____________________.

103.

Seasons on Earth are caused by the ____________________ of Earth’s axis as Earth revolves around the sun.

104.

The force that pulls the moon toward Earth is called ____________________.

105.

According to the ____________________ theory, the moon was formed when a Mars-sized object collided with Earth.

106.

The times that day and night are of equal length are called ____________________.

107.

Tides are caused by the force of ____________________ from the sun and moon acting on Earth’s waters.

108.

The lighted half of the moon faces away from Earth during the ____________________ phase.

109.

Any object that revolves around another object in space is called a ____________________.

110.

When a large ____________________ strikes Earth, it can create a crater.

111.

The middle layer of the sun’s atmosphere is the ____________________.

112.

A lunar eclipse can only occur during the ____________________ phase.

113.

A protostar becomes a star when energy is released by the process of ____________________.

114.

The sun’s energy comes from the process of ____________________, in which hydrogen atoms form helium.

115.

Nuclear fusion occurs in the ____________________, or center, of the sun.

116.

A loop of gas that links different parts of sunspot regions is a ____________________.

117.

The device astronauts used to study extremely weak moonquakes was a ____________________.

118.

Astronomers use ____________________ magnitude to compare the brightnesses of stars.

119.

The atmospheres of the gas giants are composed mainly of ____________________.

120.

A spectrograph breaks the light from an object into a(n) ____________________, or range of different colors, and photographs it.

121.

The most massive stars collapse to form ____________________ when they die.

122.

The length of a star’s life is determined by its ____________________.

123.

Few comets pass near Earth because their ____________________ are so elliptical.

124.

The apparent change in position of an object when viewed from two different places is called ____________________.

125.

The sun and moon seem to move mainly because of the ____________________ of Earth on its axis.

126.

The distance between the crest of one wave and the crest of the next wave is the wave’s ____________________.

127.

The type of light humans can see is ____________________ light.

128.

Astronomers can determine the temperature of a star by using an instrument called a(n) ____________________.

129.

Of all the planets, only ____________________ is known to have liquid water.

130.

The solar wind pushes gas away from a comet. Gas and dust form the comet’s ____________________.

131.

According to the big bang theory, the universe formed about ____________________ years ago.

132.

A dying giant star can suddenly explode, becoming a(n) ____________________.

133.

Astronomers can detect a binary star system called a(n) ____________________ when one star dims and brightens.

134.

The first object to form in our solar system when a nebula collapsed was the ____________________.

135.

The moon’s average density is about the same as the density of Earth’s ____________________ layers.

136.

Regions on the surface of Mars have patterns that appear to have been made by ____________________.

137.

Most ancient astronomers thought that all celestial objects revolved around ____________________.

138.

A device that detects radio waves from objects in space is called a(n) ____________________ telescope.

139.

A galaxy that does not have a regular shape is classified as a(n) ____________________ galaxy.

140.

The round pits on the moon are called ____________________.

141.

____________________ rockets make it possible to travel into space.

142.

A(n) ____________________ galaxy has a characteristic pinwheel shape.

143.

Kepler discovered that Mars’ orbit is a(n) ____________________.

144.

Telescopes work by detecting forms of ____________________ radiation.

145.

A tide with the least distance between low and high tides is called a ____________________ tide.

146.

The planets that are closer to the sun than Earth are Venus and ____________________.

147.

The moon can be seen from Earth because ____________________ reflects off the moon.

148.

The tendency for an object in motion to remain in motion is called ____________________.

149.

The only outer planet with a solid surface is ____________________.

150.

A rocket burns fuel to produce ____________________, which create a force that moves the rocket when it is expelled.

Short Answer

Use the diagram to answer each question.

151.

Where is the moon in relation to Earth and the sun during phase B?

152.

Approximately how much time passes between H and B?

153.

Which two phases are gibbous moons?

154.

In phase E, from what direction is the sun shining?

155.

Number the phases of the moon in the order that they occur, beginning with the new moon as number 1.

156.

What are the phases shown in A and D called?

Use the diagram to answer each question.

157.

Compare our sun to Alpha Centauri A in terms of color, brightness, and surface temperature.

158.

Describe three features of the star Deneb.

159.

State how Barnard’s star and Mira are similar.

160.

Name the stars on the diagram that are blue or blue-white.

161.

Using the figure, name a star that is very dim and red in color.

162.

Suppose you wanted to observe the star Aldebaran. What clues would you use to help you identify it?

Use the diagram to answer each question.

163.

What objects are found at 5? Why are they not considered to be planets?

164.

Name object 9 and explain why it appears different from the other gas giant planets.

165.

What is object 7? Compare its size and orbit to those of the planets.

166.

Write the name of the planet that is labeled with each number. 1________ 2________ 3________ 4________

167.

Explain how inertia and gravity combine to keep the planets in their orbits.

168.

Which planet is closer to the sun, the one labeled 10 or the one labeled 11? Is it always closer to the sun?

Use the diagram to answer each question.

169.

How many tides will occur on Monday? How many are high tides? How many are low tides?

170.

Predict the height of the next low tide that will occur after the 5.9-m tide on Thursday.

171.

Are the tides approaching a spring tide or a neap tide? Explain.

172.

What is the difference in height between low tide and high tide on Wednesday?

173.

If you were piloting a ship to a town on Baffin Bay, what would be the best day and time to arrive at the town? Explain.

174.

Describe how the height of the tides changes from Monday to Thursday.

Use the diagram to answer each question.

175.

What is a supernova?

176.

When a star begins to run out of fuel, what two types of stars can it become?

177.

What happens to small and medium stars when they run out of fuel?

178.

How does a neutron star form?

179.

How does a star’s life begin?

180.

What determines whether a star will form a black hole when it dies?

Use the diagram to answer each question.

181.

Identify the objects in area D. Explain why they appear to be darker than the other parts of the sun.

182.

Identify area F. Describe what happens in this area.

183.

Identify area B. Describe its appearance during a total solar eclipse.

184.

Identify area C and define it.

185.

Identify area E and define it.

186.

Identify area A. When is this area visible to the human eye?

Essay

187.

Explain why it is warmer near the equator than it is near the poles.

188.

Why do people on Earth always see the same side of the moon?

189.

What is a space station? Name some uses of space stations.

190.

Define parallax and explain how astronomers use it to measure distances to stars.

191.

Name three conditions needed for life as we know it to exist. Where in the solar system are these conditions found?

192.

Describe what happens to a small star, a medium star, and a giant star when each runs out of fuel.

193.

Explain how day and night occur.

194.

Explain the difference between apparent magnitude and absolute magnitude of stars.

195.

Compare and contrast a reflecting telescope and a refracting telescope.

196.

Compare and contrast spiral and elliptical galaxies.

197.

Explain how a spectrograph provides information about a star’s chemical composition.

198.

Describe how scientists think the moon was formed.

199.

Describe how the solar system probably formed.

200.

Why do scientists think Europa might be a good place to look for extraterrestrial life?

201.

Explain how a lunar eclipse differs from a solar eclipse.

202.

What are two reasons the sun is important?

203.

Explain why some scientists do not consider Pluto to be a planet.

204.

Explain why spring tides are higher than all other tides.

205.

Explain why the outer planets did not lose the gases in their atmospheres.

206.

How are Earth and Venus similar? How is Venus different from Earth?

207.

What caused Galileo to accept the theory that the planets revolve around the sun?

208.

Algol is a star system with two stars. Explain why one star sometimes seems to disappear.

209.

Explain what happens as a three-stage rocket is launched and travels up into space.

210.

Describe the differences among a meteoroid, a meteor, and a meteorite.

Modified True/False

Indicate whether the sentence or statement is true or false. If false, change the identified word or phrase to make the sentence or statement true.

211.

Europa’s surface is made of liquid water.

212.

The four inner planets are gas giants.

213.

Scientists learned much about the moon by studying rocks brought back by astronauts.

214.

The phases of the moon depend on how much of the lighted side of the moon can be seen from Earth.

215.

Pluto has more moons than any other outer planet.

216.

Sunspots are areas on the sun that are cooler than the gases surrounding them.

217.

The brightness of a star as seen from Earth is its apparent magnitude.

218.

The surfaces of the largest planets are solid.

219.

A solar eclipse occurs when the moon moves directly between the sun and Earth.

220.

Gases expelled from the rear of a rocket push the rocket in the same direction as the gases.

221.

A reflecting telescope uses a mirror to focus light onto a small area.

222.

Most galaxies are moving away from each other, which means the universe is contracting.

223.

The beginning of spring in the Northern Hemisphere is marked by the vernal equinox.

224.

A star that has no fuel but glows faintly is a black dwarf.

225.

Day and night are caused by Earth’s revolution on its axis.

226.

The moon’s average density is greater than the density of Earth’s outer layers.

227.

Earth is at the center of the solar system in the geocentric model.

228.

A comet or asteroid can break up to form a chunk of rock called a meteoroid.

229.

Maria are low areas, once flooded with lava, on the moon’s surface.

230.

A tide with the greatest distance between low and high tides is called a neap tide.

231.

The sun is part of an elliptical galaxy.

232.

Chunks of ice and dust that usually have long elliptical orbits are called comets.

233.

A star system has at least three stars.

234.

The part of the sun that can be seen in a photograph is the photosphere.

235.

The solar system was formed after the Milky Way galaxy was formed.

236.

Radio waves are shorter than waves of visible light.

237.

Stars with less mass will last longer than stars with more mass.

238.

The inner planets are large and have rocky surfaces.

239.

Astronomers measure distances to stars in units called kilometers.

240.

Astronauts and equipment are launched into space mainly by space stations.