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Flashcards in FINAL EXAM Deck (304):
1

Main sequence stars are in hydrostatic equilibrium, which is a balance between gravitational forces and...

forces due to gas pressure

2

The lower-left corner of the H-R diagram contains...

hot stars that are NOT very luminous

3

The lower-right corner of the H-R diagram contains

cool stars that are NOT very luminous

4

The upper-left corner of the H-R diagram contains

hot stars that are very luminous

5

The upper-right corner of the H-R diagram contains

cool stars that are very luminous

6

While a star is in its protostar phase, its main source of energy is

nuclear fusion

7

The net result of a proton-proton chain reaction is that

four hydrogen nuclei combine to produce a helium nucleus with the release of neutrinos and radiant energy

8

Main-sequence stars with masses much greater than the Sun’s mass primarily use ____for their fusion reactions.

the CNO cycle

9

Main-sequence stars with masses of about the Sun’s mass or less primarily use ____for their fusion reactions.

the proton-proton chain

10

Stars like the Sun do not develop iron cores during their lifetimes because

their cores are not hot enough

11

Chemical elements heavier than iron are/were formed

during supernova explosions

12

Data collected over many years by the SNO in Sudbury, Ontario provided strong evidence for the standard theory of

energy production in the Sun

13

Astronomers distinguish between Type Ia supernovae and Type II supernovae by

detecting the absence or presence of hydrogen lines in their spectra

14

The atomic nuclei of oxygen that we breathe were synthesized

by a star fusing lighter nuclei in its interior.

15

As the mass of the iron core of a star increases, its diameter

decreases.

16

Astronomers determine the mass of a black hole by measuring

the orbital period and radius of a star or material orbiting the black hole

17

The more massive a black hole is, the _____ is its Schwarzschild radius.

larger

18

You observe a clock dropped towards a black hole from a high orbit, and notice that

time on the clock runs slower as it approaches the black hole, and light emitted from the clock is increasingly redshifted.

19

When the core of a star begins to run out of hydrogen, the next stage in the star’s evolution is that

the star’s core contracts and its outer layers expand

20

A planetary nebula is a remnant of

the end-stage evolution of a medium-mass star

21

When a star that has a mass of more than twenty solar masses leaves the main-sequence phase of its life, it will eventually become a

either a black hole or neutron star

22

As a contracting protostar heats up, if the core temperature reaches 10 million degrees K, then

hydrogen fusion begins and the protostar becomes a main-sequence star.

23

Reflection nebulae are

blue

24

Emission nebulae are

red.

25

When the Sun leaves the main-sequence phase of its life, it will eventually become a

white dwarf

26

A binary pulsar

closely orbits at least one other star

27

If a collapsing star has a mass less than the Chandrasekhar limit, then it

eventually becomes a white dwarf.

28

White dwarfs typically have sizes that are approximately the size of

the Earth.

29

The surface temperature of a white dwarf is approximately

tens of thousands of degrees

30

The remnant of a type II supernova is

either a black hole or a neutron star.

31

As the fusion of progressively heavier nuclei takes place in the later stages in the lifetime of a very massive star, each stage of fusion takes

progressively less time.

32

In a type II supernova, most of the energy produced in the explosion is carried away by

neutrinos.

33

A pulsar is a rotating

neutron star

34

Precision measurements on binary pulsars have provided strong evidence for

Einstein’s theory of gravity

35

If the Sun were suddenly and magically replaced by a black hole of the same mass, then the planets in our solar system would

[No change in planetary motions would occur.]

36

The escape velocity from within the event horizon of a black hole is

greater than the speed of light

37

It was first confirmed that separate galaxies existed outside our own Milky Way galaxy

in the 1900s

38

With the aid of modern telescopes, the number of galaxies currently visible is in the

billions

39

Spiral galaxies contain mostly

Population I stars and tend to be blue

40

Spiral galaxies typically contain

a lot of gas and dust

41

The expansion of the space between galaxies has an effect on light travelling through space,

shifting its wavelength towards the red end of the spectrum

42

Collisions between galaxies are much more common than collisions between individual stars because

the distances between galaxies in a cluster are comparable to their sizes, but the distances between stars in a galaxy are much greater than their sizes.

43

A quasar is

a powerful source of energy in the active core of a distant galaxy

44

Seyfert galaxies are _____ that have small, highly luminous nuclei

spiral galaxies

45

The Higgs boson was first detected

by the LHC in 2012.

46

One of the predictions of Einstein’s theory of general relativity is that light from distant stars should have its path bent by

the gravitational effect of matter between us and the source of the light.

47

Data from the WMAP and Planck satellite observatories suggest that the the universe

(a) is flat (overall). (b) has accelerating expansion. (c) will probably expand forever

48

In the first minute or so after the Big Bang, _____ could not exist because it was too hot.

atomic nuclei beyond hydrogen

49

We know that the Milky Way galaxy has spiral arms by observing the distribution of

associations of hot and luminous young stars.

50

The amount of ordinary matter in the universe is currently thought to be _____ the amount of dark matter.

much less than

51

About ____ of the mass of the solar system is contained in the Sun.

99.9%

52

The diameter of the Sun is about _____ times the diameter of the Earth

100

53

The solar nebula theory proposes that

planets form in rotating disks of gas and dust around young stars.

54

The terrestrial planets are _____ the Jovian planets

less massive than

55

The terrestrial planets are _____ the Jovian planets

more dense than

56

The terrestrial planets are typically _____ than the Jovian planets.

warmer

57

The planet Venus has ____ moon(s).

0

58

The planet _____ has dozens of moons

Jupiter

59

The ages of rocks found in the solar system are often determined by using the properties of

radioactive elements

60

The inner planets have a much higher concentration of _____ than the outer planets

iron

61

There is strong evidence that Venus was once geologically/volcanically active. T or F?

True

62

The age of the planets is about?

5 billion years

63

The process by which planetary material separates inside a planet is known as

differentiation.

64

Most of the craters in the solar system appear to have been formed about?

4 billion years ago

65

Small chunks of rock that leave a streak of light as they fly through Earth’s atmosphere are called?

meteors

66

Small chunks of rock that fly through the solar system are called?

meteoroids

67

Small chunks of rock that have landed on Earth after coming from outer space are called?

meteorites

68

The Chicxulub crater is

a large crater on Earth that is associated with the extinction of the dinosaurs

69

Mars has a higher albedo than Venus? Tor F?

False

70

The magnetic field of ____ is about 10 times stronger than Earth’s magnetic field?

Jupiter

71

Jupiter’s atmosphere is_____ Saturn’s atmosphere

warmer than

72

The largest mountain in the solar system is on the surface of

Mars.

73

Gaps in the rings of Saturn are caused by

orbital resonances with some of Saturn’s moons

74

The mass of the Milky Way galaxy is determined by carefully measuring

motions of the stars within the galaxy

75

The cosmological flatness problem is that

the early universe must have contained a very precise amount of matter in order that space-time be very nearly flat.

76

In the Milky Way galaxy, star formation is most common

in the spiral arms.

77

The fact that galaxies are generally moving away from each other is expressed by

Hubble’s law

78

The following observed properties of cosmic microwave background radiation provide strong evidence for the Big Bang theory of the formation of the universe.

its temperature and similarity in all directions

79

The cosmic microwave background radiation was first observed using

a microwave antenna

80

By the first few minutes after the Big Bang, the number of hydrogen atoms in the universe was greater than the number of helium atoms by a factor of about

3

81

The protons, neutrons, and electrons that make up the ordinary matter in our universe were formed ____ after the Big Bang

within the first few seconds

82

If the average density of the universe is large enough, then the universe

will eventually stop expanding and re-collapse into a highly compact state

83

If the average density of the universe is small enough, then the universe

will expand indefinitely

84

Which mechanism is most responsible for generating the internal heat of Io that drives its volcanic activity?

tidal heating

85

Most asteroids are

irregular in shape, and battered by impact cratering

86

Asteroids and comets in our solar system

have been studied extensively by numerous unmanned spacecraft that have flown close by them.

87

Meteor showers on Earth occur when

the Earth passes near the orbit of a comet

88

Greenhouse gases

reflect infrared light

89

Which of these planets has the lowest atmospheric pressure at its surface?

Mars

90

Which of the following is not a greenhouse gas

nitrogen (N2

91

A carbonaceous chondrite is a type of

stony meteorite

92

The nucleus of a comet resembles

a dirty snowball

93

Most comets originate

in the Kuiper belt if they have short periods and in the Oort cloud if they have long periods

94

Concerning planets orbiting other stars besides our Sun,

many have been observed, and research is ongoing

95

Main sequence stars are in hydrostatic equilibrium, which is a balance between

outward gas pressure and inward gravitational force

96

In the inner layers of the Sun, the primary way energy is transported outwards is

radiation

97

In the outer layers of the Sun, the primary way energy is transported outwards is

convection

98

Stellar models are

computer programs that use the laws of physics to calculate what the detailed properties of a star might be, based on the star’s mass and radius.

99

Hydrogen fusion is a process in which

hydrogen nuclei join to produce heavier nuclei, with a release of energy

100

The net result of a proton-proton chain reaction is that

four hydrogen nuclei combine to produce a helium nucleus with the release of neutrinos and radiant energy.

101

Fusion reactions in a gas are rare unless the gas is extremely

hot.

102

The temperature of the Sun’s core is about

15,000,000 K.

103

Data collected over many years by the SNO in Sudbury, Ontario provided strong evidence for the standard theory of

energy production in the Sun

104

For main-sequence stars, the more massive a star is

the more luminous it is

105

For the most part, protostars form

deep inside clouds of dust and gas

106

The dramatic changes that occur towards the end of a high-mass star’s lifetime are initiated by

the star’s core running out of hydrogen

107

If the mass of Star A is significantly greater than the mass of Star B, then

the lifetime of Star A is shorter than the lifetime of Star B

108

Helium fusion in the core of a red giant star produces

carbon and oxygen

109

A planetary nebula is a remnant of

the end-stage evolution of a medium-mass star

110

Giant molecular clouds, from which stars will eventually form, are

cold and dense

111

As a contracting protostar heats up, if the core temperature reaches_____ then hydrogen fusion begins and the protostar becomes a main-sequence star.

10 million degrees K

112

“Stars” with masses of less than about 0.08 solar masses never get hot enough to fuse hydrogen into helium, and are called

brown dwarfs

113

The non-fusing core that remains immediately at the end of the lifetime of a medium mass star is called a

white dwarf

114

The main-sequence lifetime of a star depends on its

mass and luminosity

115

Eventually, a white dwarf will stop emitting light, but this is expected to take

several trillion years

116

When rotating stars contract, their rotation rates typically

increase

117

A neutron star is a remnant of a

type II supernova

118

A black hole is a remnant of a

type II supernova

119

As the fusion of progressively heavier nuclei takes place in the later stages in the lifetime of a very massive star, each stage of fusion takes

progressively less time

120

In the evolution of a very massive star, energy production declines when the core contains primarily

iron

121

The famous SN1987A, discovered by Canadian astronomer Ian Shelton, is

a Type II supernova

122

A pulsar is a rotating

neutron star

123

Precision measurements on binary pulsars have provided strong evidence for

Einstein’s theory of gravity

124

Astronomers search for black holes by examining binary systems in which an invisible component has mass greater than 3 solar masses and is a strong emitter of

X-rays

125

It was first confirmed that separate galaxies existed outside our own Milky Way galaxy

in the twentieth century

126

Spiral galaxies contain mostly

Population I stars and tend to be blue.

127

Spiral galaxies typically contain

a lot of gas and dust

128

Cosmological redshift is a result of

space between galaxies expanding

129

A common result of a galaxy collision is

gravitational distortion of one or both of the galaxies.

130

The period of the luminosity variation of a quasar provides insight into the quasar’s

size

131

According to the Big Bang theory, _____ formed about 380 thousand years after the Big Bang.

neutral hydrogen atoms

132

One of the predictions of Einstein’s theory of general relativity is that light from distant stars should have its path bent by

the gravitational effect of matter between us and the source of the light.

133

Data from the WMAP and Planck satellite observatories suggest that the the universe

(a) is flat (overall). (b) has accelerating expansion. (c) will probably expand forever.

134

We can observe the centre of the Milky Way galaxy using

radio waves

135

The amount of ordinary matter in the universe is currently thought to be _____ the amount of dark matter.

much less than

136

The Milky Way is

a spiral galaxy

137

The mass of the Sun is about ______ times the mass of the Earth

300,000

138

The solar nebula theory proposes that

planets form in rotating disks of gas and dust around young stars

139

The terrestrial planets are _____ than the Jovian planets.

smaller

140

The terrestrial planets are_____ the Jovian planets.

more dense than

141

The orbits of the planets around the Sun lie

approximately in a plane

142

The planet ____ rotates “backwards” compared to the other planets.

Venus

143

The planet _____ rotates “on its side” compared to its orbital motion.

Uranus

144

The chemical composition of the Sun’s atmosphere is _____ the chemical composition of the solar nebula.

very similar to

145

The cores of terrestrial planets are primarily composed of

iron and nickel.

146

The outer planets have a much higher concentration of ______ than the inner planets

hydrogen

147

The process by which small solid particles stick together to form larger particles, as part of the formation of planetesimals, is known as

accretion

148

Comets are

chunks of frozen gases with solid particles mixed in

149

The two moons of Mars, Phobos and Deimos, are most likely

to be captured asteroids

150

The atmosphere of _____ is extremely hot, about 90 times more dense than Earth’s atmosphere, and is about 95% carbon dioxide.

Venus

151

The atmosphere of _____ is cool, about 1% as dense as Earth’s atmosphere, and is about 95% carbon dioxide.

Mars

152

Rings are found around

Jupiter, Saturn, Uranus, and Neptune.

153

MACHOs and WIMPs are hypotheses intended to explain

dark matter

154

In the Milky Way galaxy, star formation is most common

in the spiral arms

155

The historical significance of Hubble’s law is that it helped to establish the fact that

galaxies are generally moving away from each other.

156

The following observed properties of cosmic microwave background radiation provide strong evidence for the Big Bang theory of the formation of the universe.

its temperature and similarity in all directions

157

The cosmic microwave background radiation was first observed

in the 1900s.

158

Observed fluctuations in the cosmic microwave background are currently ____ , which implies that matter was almost uniformly distributed in the early years after the Big Bang.

tiny

159

. The current temperature of the cosmic microwave background radiation is approximately

3 K.

160

If the average density of the universe is small enough, then the universe

will expand indefinitely

161

The latest observations on the overall curvature of the universe suggest that the universe

is nearly flat.

162

The tail of a comet is gas and dust

pushed off the comet by the Sun’s heat and radiation pressure.

163

The bright streak of light seen when a small object from the solar system flies through the atmosphere is caused by

frictional heating

164

The source of most meteorites is

comets

165

Most asteroids in the main asteroid location of the solar system have orbits that are

prograde, nearly circular, and near the ecliptic

166

The average spacing between asteroids in the main asteroid location of the solar system is about

1 million km

167

Asteroids in the asteroid belt are made up of

iron. (b) silicates (rock). (c) organic compounds

168

Most meteorites that strike the Earth are

stones

169

Concerning planets orbiting other stars besides our Sun,

many have been observed, and research is ongoing

170

If the lifetime of Star A is significantly greater than the lifetime of Star B, then

the mass of Star A is less than the mass of Star B.

171

The youngest stars

are typically surrounded by clouds of gas and dust.

172

Dark nebulae emit significant amounts of

infrared radiation

173

Emission nebulae emit large amounts of

red light

174

Giant molecular clouds

are regions of space in which stars form

175

Giant molecular clouds

typically contain clumps.

176

The proton-proton chain

is the major way that low-mass stars stars fuse hydrogen into helium.

177

Hydrostatic equilibrium is the state of a star when it

is on the main sequence

178

As fusion proceeds in the core of a star, the number of particles _____, and so the temperature of the core must ______to maintain core pressure.

decreases, increase

179

The helium flash is the onset of fusion of ____ in the core of a star

helium into carbon

180

Nuclear fusion takes place in a white dwarf mainly in

[Virtually no nuclear fusion occurs in a white dwarf.]

181

Planetary nebulae often appear approximately ring-like because

they are approximately spherical shells, and only appear ring-like because of our viewing perspective.

182

Distances to the most distant galaxies are determined using

Type Ia supernovae.

183

The escape velocity from a black hole is

greater than the speed of light

184

The idea that the Milky Way galaxy is disk-shaped was first proposed by

Thomas Wright and Immanuel Kant

185

Our location in the Milky Way galaxy was first established by

Harlow Shapley

186

Our location in the Milky Way galaxy was first determined using measurements of distances to

globular clusters

187

The halo of the Milky Way contains

stars, star clusters, but no gas and dust.

188

The stars in the bulge of the Milky Way are similar to the stars in the halo, but the bulge also contains

some hot, luminous stars

189

“Rotation curves” for stars at various positions in the Milky Way, first measured by Vera Rubin, do not match observed luminous matter in the galaxy. This is strong evidence for the presence of

dark matter in the Milky Way.

190

A MACHO is

a massive astrophysical compact halo object

191

A WIMP is

a weakly-interacting massive particle

192

Elliptical galaxies contain mostly

Population II stars and tend to be red

193

The mass of every observed elliptical galaxy

might be more or less than the mass of the Milky Way galaxy.

194

Lenticular (S0) galaxies

have very large nuclei and barely visible spiral arms

195

An irregular galaxy

contains a chaotic mix of gas and dust with no obvious nucleus and no spiral arms.

196

The number of elliptical galaxies we observe is _____ the number of spiral galaxies we observe

about half

197

Superclusters

are formed of clusters of galaxies grouped together

198

The Big Bang theory explains in detail

how the universe was in a very hot dense state in the past and has expanded ever since.

199

The Hubble time

gives an approximation for the age of the universe

200

There is plenty of good evidence for the Big Bang theory, including the abundance of

hydrogen and helium in the universe

201

Astronomers made a startling observation in 1998, that about 4 billion to 5 billion years ago

the expansion of the universe began to accelerate

202

The Jovian planets have orbits that are typically

farther from the Sun than the terrestrial planets

203

Pluto is no longer considered to be a planet because

it has not “cleared its orbit;” that is, it is not the only body of its size at its approximate distance from the Sun.

204

Kepler’s first law states that

the orbit of each planet is an ellipse, and the Sun is at one focus of the ellipse

205

Kepler’s third law relates a planet’s ______ to its ______.

distance from the Sun, orbital period

206

The planet in our solar system with the smallest density is

Saturn.

207

The planet in our solar system that is closest to the Sun is

Mercury

208

The planet in our solar system that is farthest from the Sun is

Neptune

209

Which planet has the highest reflectivity (albedo)?

Venus

210

Which planet has the highest surface temperature?

Venus

211

Which planet has the highest surface atmospheric pressure?

Venus

212

The age of the solar system is about

4.6 billion years

213

Some evidence of intense bombardment in the solar system by leftover debris is

many impact craters on terrestrial planets and nearly all satellites.

214

Impact craters differ from volcanic craters because impact craters

have floors that are lower than surrounding terrain

215

The structure of the Earth’s core is studied by analyzing

the propagation of earthquake waves

216

The theory of plate tectonics (continental drift) was proposed by

Alfred Wegener in 1912

217

The theory of continental drift proposes that

long ago the continents were very close together, and they have been gradually drifting apart ever since.

218

Where major continental plates meet, one finds an increase in

volcanic activity and earthquakes.

219

More volcanoes are found on _____ than on any other planet

Venus

220

Besides a planet’s primary atmosphere, another main source of gases in the atmospheres of most planets in the solar system is

volcanic activity

221

The planets that still have much of their primary atmospheres are

all Jovian planets

222

The most abundant gas in the atmosphere of Venus is

carbon dioxide

223

A planet can lose its atmosphere if

its surface is too hot

224

The temperature of a planet is determined primarily by the planet’s

distance from the Sun and its reflectivity

225

Mercury’s atmosphere

is almost nonexistent

226

The most abundant gas in Earth’s atmosphere is

nitrogen

227

Venus has a much higher surface temperature than Earth, primarily because

of the greenhouse effect

228

The concentration of oxygen in the Earth’s atmosphere increased dramatically about 2 billion years ago because

of the appearance of blue-green algae

229

The atmosphere of Mars is

much less dense than the atmosphere of Earth, because Mars has a smaller surface gravity

230

Tidal forces exerted by the Moon on the Earth cause

two tidal bulges, one each on the sides of the Earth facing towards and away from the Moon.

231

On Earth there is a high tide and a low tide approximately

twice per day.

232

Tidal forces cause the Earth’s rotational rate to _____ by about 0.002 seconds per century.

decrease

233

Tidal forces cause the Moon (and many other satellites in the solar system) to have synchronous rotation. This means that the Moon’s rotational period is synchronized with

the Moon’s orbital period

234

The rings around the planet Saturn have gaps, the largest of which is named after the astronomer

Cassini

235

The rings of Saturn were discovered by the astronomer

Galileo

236

The rings of Jupiter were discovered by

the Voyager 1 space probe

237

The rings of Saturn are about

100 m thick

238

The gaps in the rings of Saturn are caused by

resonant gravitational attraction from the satellite Mimas

239

Comets

slowly shift their position in the sky from night to night and remain visible for a few days up to a few months

240

The nucleus of a comet resembles a “dirty snowball,” and is made up of water ice, small amounts of

rocks, and frozen ammonia, methane, and carbon dioxide.

241

The coma of a comet is a glowing ball of gas, which for most comets has a diameter between

100,000 km and 1,000,000 km

242

The orbits of most comets are

not in the plane of the ecliptic

243

Most periodic and short-period comets originate in

the Kuiper belt

244

The largest asteroid in the solar system is

Ceres

245

Trojan asteroids have orbits that are

near Jupiter’s orbit, and about 60◦ ahead of and behind Jupiter.

246

Smaller asteroids tend to have

irregular shapes.

247

The Kirkwood gaps are

areas in the asteroid belt where there are relatively few asteroids

248

The majority of asteroids are

C-asteroids

249

C-asteroids are made up of

silicates mixed with dark carbon compounds

250

M-asteroids are made up of

metals such as nickel and iron

251

S-asteroids are made up of

silicates

252

Solid objects that are smaller than asteroids and orbit the Sun are called

meteoroids.

253

If the mass of Star A is significantly greater than the mass of Star B, then

the lifetime of Star A is less than the lifetime of Star B.

254

A cloud of gas and dust that is observable at visible wavelengths is called

a nebula.

255

Nebulae that are reddish in colour are called

emission nebulae

256

Nebulae that are bluish in colour are called

reflection nebulae

257

If a clump in a giant molecular cloud is massive enough, it will begin to contract; as a result, it becomes hotter because

some of the contracting clump’s gravitational potential energy is converted to thermal energy

258

The evolution of a main-sequence star is influenced primarily by

its mass.

259

Low-mass stars, with masses less than about 0.5 solar masses, tend to be dim and cool, and are called

red dwarfs.

260

Hydrostatic equilibrium is a balance between a star’s

internal pressure and gravity

261

Although planetary nebulae are typically approximately spherical, they appear to us to be shaped somewhat like a

ring

262

If a collapsing star has a mass greater than the Chandrasekhar limit, then it

becomes a neutron star or black hole

263

The range of observed radii of white dwarfs is approximately between

the radius of the Earth and twice the radius of the Earth.

264

Eventually, a white dwarf will stop emitting light, but this takes

a period of time comparable to the age of the universe

265

Planetary nebulae emit light because

they absorb ultraviolet light from a central white dwarf and then emit visible light.

266

A type Ia supernova occurs because of

matter from a nearby star falling onto the surface of a white dwarf, becoming compressed and heated, and eventually resulting in an explosion.

267

A type II supernova occurs because of

the core collapse of a high-mass star

268

Observations by _____ first showed that the Milky Way consists of many faint stars.

Galileo in 1609.

269

_____ established our location in the Milky Way by measuring the distances to _____

Harlow Shapley, globular clusters

270

The diameter of the Milky Way is approximately

100,000 light years

271

Henrietta Swan Leavitt observed that there is a relationship between ______ for the variable stars that she studied.

period and luminosity

272

The disk of the Milky Way contains

stars, star clusters, gas and dust

273

Dark matter was discovered by observing that

the motions of disk stars (i.e., rotation curves) in spiral galaxies differed from those expected by applying Kepler’s third law.

274

The composition of the universe is currently inferred to be approximately

5% ordinary matter, 25% dark matter, 70% dark energy.

275

The diameter of the Sun is about _____ times the diameter of the Earth

100

276

The planet closest in size to Earth is

Venus

277

The distance of Jupiter from the Sun is about ___AU (Astronomical Units).

5

278

Pluto is now considered to be

a dwarf planet

279

The only planets in the solar system that do not have any known satellites (i.e., moons) are

Mercury and Venus

280

Jovian planets have longer rotation periods (days) than terrestrial planets. T or F?

False

281

The planet in our solar system with the largest diameter is

Jupiter

282

As seen from above the Earth’s north pole

all planets orbit the Sun counterclockwise

283

lanets move around the Sun in _____ orbits with the Sun at one focus.

elliptical

284

As viewed from above the Earth’s north pole, all planets spin counterclockwise except for

Venus and Uranus

285

The best current theory we have for the formation of the solar system hypothesizes that the solar system formed because of

the collapse of a spinning cloud of gas and dust.

286

On average, disk stars in the Milky Way contain ____ percentage of heavy elements than stars in the bulge and halo.

a greater

287

The Milky Way galaxy makes one rotation in about

230 million years

288

To determine distances to nearby galaxies, up to 100 million light years away, astronomers use

the method of Cepheid variables

289

To determine distances to galaxies farther than 100 million light years, astronomers use

the method of globular clusters

290

Radio galaxies are galaxies that

emit intense radio waves

291

Hubble’s law describes a relationship between

the distance of a galaxy and its recession speed.

292

One can infer whether a galaxy is receding from us, or approaching us, and its relative speed, by analyzing its spectral

redshift

293

Observations of cosmic microwave background radiation provide strong evidence for

the Big Bang theory for the evolution of the early universe

294

The cosmic microwave background radiation was first observed by

Arno Penzias and Robert Wilson of Bell Laboratories.

295

An estimate for the age of the universe can be obtained

by taking the reciprocal of the Hubble constant

296

At the beginning of the recombination era, about 400,000 years after the Big Bang, the universe had cooled enough that

protons and electrons could recombine into hydrogen atoms

297

The ultimate fate of the universe depends on

the average density of matter and energy in the universe

298

The cosmological constant is

the constant in Einstein’s equation that corresponds to dark energy

299

If the average density of the universe is large enough, then the universe

will eventually stop expanding and re-collapse into a highly compact state.

300

If the average density of the universe is small enough, then the universe

will expand indefinitely.

301

Measurements of recession speeds of distant galaxies suggest that

we might be anywhere in the universe, because all observers would see distant galaxies all receding away from them in about the same way

302

The largest asteroid in our solar system, called Ceres, has a diameter of about

1,000 km

303

Most asteroids in the main asteroid location of the solar system have orbits that are

prograde, nearly circular, and near the ecliptic

304

The average spacing between asteroids in the main asteroid location of the solar system is about

1 million km.