Astronomy 109 - Final Exam

Front 1

Which photons have the least energy out of infrared, red, ultraviolet, blue, green?

Back 1

Infrared photons have the least energy because the highest frequency.

Front 2

When is a photon emitted?

Back 2

A photon is emitted from an atam when an electron jumps from a higher to a lower energy state.

Front 3

Where do most absorption lines in the solar spectrum originate?

Back 3

Most absorption lines in the solar spectrum originate in the chromosphere.

Front 4

What best describes how we know the Sun is composed of mostly hydrogen and helium right through to the core?

Back 4

The sun's low density requires that heavier elements must make up a tiny fraction. If there were a large fraction of heavy elements, the average density of the Sun would be larger than we measure.

Front 5

What pieces of information are obtained directly from a good spectrum of a star?

Back 5

From the spectrum of a star we can obtain the surface temperature of the star, the chemical composition of the star, the rotation rate of the star, and the speed of the star towards or away from us.

Front 6

What does fusion in the center of the Sun convert hydrogen into?

Back 6

Fusion in the center of the Sun converts hydrogen into helium, neutrinos and energy.

Front 7

Why do fusion reactions occur in the core of the Sun?

Back 7

Fusion reactions occur in the core of the Sun is that the reactions require very high temperatures and densities.

Front 8

What statements would effect the stability of the nuclear reaction rate of the Sun?

Back 8

An increased nuclear reaction rate would make the center of the Sun hotter, the reaction rate decreases if the density is reduced, higher pressure in the Sun's center would cause it to expand, and hotter center would have higher pressure.

Front 9

The theory of energy generation in the Sun predicts many neutrinos should be produced and efforts were made to detect them on Earth. What was the solar neutrino problem?

Back 9

Some solar neutrinos were detected, but not many as predicted. Since then, we have detected them.

Front 10

How do oscillations of the sun reveal themselves as?

Back 10

Oscillations of the sun reveal themselves as small rising and falling motions of the surface.

Front 11

The average density of the terrestial planets is larger than that of typical rock. What does this tell us about the interior of these planets?

Back 11

This tells us that there is a large amount of a denser substance, like iron, inside each planet, to make the average density a ot higher than that of the surface rocks.

Front 12

What does the fact that the planets are differentiated imply?

Back 12

It implies that the low density rock floated on top of dense metal at some time in the past when the planet was melted.

Front 13

How do greenhouse gases interact with visible light and infrared radiation?

Back 13

Greenhouse gases are transparent to visible light but absorb infrared radiation.

Front 14

What are four important consequences of the formation of the oceans on Earth for the Earth's atmosphere today?

Back 14

Important consequences were that most of the water was removed from the atmosphere, most of the carbon dioxide was removed from the atmosphere, the greenhouse effect was substantially reduced, and plant life in oceans produced free oxygen.

Front 15

What is true about both the atmospheres of Earth and Venus?

Back 15

Both Earth and Venus' secondary atmospheres were probably quite similar in size and composition.

Front 16

What are some reasons that Earth rocks are usually much younger than moon rocks?

Back 16

Earth rocks are usually much younger than Moon rocks because the moon's interior cooled much more quickly than the Earth's, the moon has no plate tectonics, erosion is much more important on the Earth than the Moon, and the Earth has extensive ongoing vocanism.

Front 17

Why do large Martian shield volcanoes, such as Olympus Mons, become larger than any on Earth?

Back 17

Martian shield volcanoes are larger than Earth volcanoes because Mars does not have plate tectonics.

Front 18

What evidence is there for permafrost below the surface of Mars?

Back 18

Evidence for permafrost below the surface of Mars is provided by outflow channels produced by sudden floods, thought to result from heating by some volcanic activity which causes sudden extensive melting of underground ice.

Front 19

In what ways is Earth unique compared to the other planets?

Back 19

The Earth is unique because it has oxygen in its atmosphere, its biosphere is teeming with life, there are large quantities of liquid water on the surface, and its lithosphere is broken into plates which move.

Front 20

Which other bodies, besides Earth, among the terrestrial planets have man-made artifacts on the surface?

Back 20

The Moon, Mars, and Venus all have man-made artifacts on their surfaces.

Front 21

Saturn has less than 1/3 the mass of Jupiter yet its diameter is roughtly 85% of Jupiter's. What does this imply?

Back 21

This implies that Jupiter is more strongly compressed than Saturn.

Front 22

How do we know Jupiter's internal composition?

Back 22

We know Jupiter's internal composition because no planet of Jupiter's mass could have such a low density unless were mostly a hydrogen-helium mixture. If Jupiter had large fractions of any other elements, it would be too dense.

Front 23

Why does Jupiter have several distinct cloud layers?

Back 23

Jupiter has several distinct cloud layers because different layers contain clouds made of gases that condense at different temperatures.

Front 24

Why are Saturn's cloud decks less colorful than Jupiter's?

Back 24

Saturn's cloud decks are less colorful than Jupiter's because they lie deeper in Saturn's atmosphere.

Front 25

All the giant planets radiate more heat than each recieves from the Sun. What are some statements about Saturn, Uranus, Neptune, and Jupiter in terms of heat radiation?

Back 25

Saturn is believed to generate its heat by helium precipitation, Uranus and Neptune are heated mostly by radioactive decays in their interiors, Saturn has finished contracting, and Jupiter is still radiating heat caused by its contraction.

Front 26

How doe we know that the surfaces of the inner Galilean moons of Jupiter are younger than those of the outer moons?

Back 26

The inner moons have few or no impact craters while the outer moons have many.

Front 27

Geological activity on several of the Galilean moons of Jupiter suggests the interiors are warmed. What is the main source of heat?

Back 27

The main source of heat on the Galilean moons is tidal heating by Jupiter.

Front 28

What are four statements about Saturn's giant moon Titan?

Back 28

Titan is too cold for liquid water to exist, it may have lakes of liquid ethane, the hazy atmosphere makes it hard to see the surface, and its atmosphere is mostly nitrogen.

Front 29

What has caused the recent interest in Saturn's moon Enceladus?

Back 29

A geyser has been seen on Enceladus, indicating it is warmed internally somehow.

Front 30

How are planetary ring systems thought to have arisen?

Back 30

Planetary rings systems are thought to arise from collisions between moons and asteroids and comets.

Front 31

What are some differences between asteroids and comets?

Back 31

Asteroids are made mostly of rock and metal, comets of mostly ice, asteroids are generally dense objects, comets are low-density objects, comets are mostly in the outar solar system, asteroids are concentrated between Mars and Jupiter, comets generally move on highly eccentric oribts, asteroids on more nearly circular oribts, asteroid orbits are close to the ecliptic, and comet orbits have no preferred plane of motion.

Front 32

What are meteor showers that occur regularly every year caused by?

Back 32

Meteor showers that occur regularly every year are cuased by debris left in the orbit of an Earth-crossing comet. The debris left behind when the ice in a comet is finally all evaporated is a cloud of dust and small rocks that are spread along the path of the comet. We see a meteor shower when the Earth passes through such a cloud.

Front 33

What are possible fates for a comet?

Back 33

Comets can end by evaporating and leaving a meteor stream, being ejected from the solar system, colliding with the Sun, and colliding with a planet.

Front 34

What is odd about Halley's comet?

Back 34

The orbit of Halley's comit must have been changed relatively recently by an encounter with a planet.

Front 35

Why do sunspots appear dark in visible light?

Back 35

Sunspots are actually quite bright but appear dark agains the brighter surrounding surface of the Sun.

Front 36

Babcock proposed a model to account for the solar cycle. What does his model account for?

Back 36

Babcock's model accounts for cyclic variations in the temperature and size of the Sun's corona, variations in the tangled and twisted form of the Sun's magnetic field, field reversals every eleven years, and cyclic variation of the number and distribution of sunspots.

Front 37

Which combination of factors is thought to be required for the generation of magnetic field in planets?

Back 37

A liquid conducting core and rotation is required for the generation of a magnetic field.

Front 38

Which terrestrial world has the strongest magnetic field?

Back 38

The Earth has the strongest magnetic field.

Front 39

The Earth's magnetic field serves to shield the surface from what?

Back 39

The Earth's magnetic field serves to shield the surface from electrically charged particles from space.

Front 40

The condensation model for the fomration of the soalr system postulates a rotating disk of gas and dust. What is the principal strengths of this model?

Back 40

The principal strength of the condensation model is that is accounts for the pattern of orbits of the planets about the Sun.

Front 41

Collisions between the planetesimals could have released enough energy to melt the merged object.

Back 41

Yeah. The heat that melted the planets is believed to have come from the collisions as they were assembled. Lots of material was left over. Comets are believed to have been formed in the outer solar system and scattered into the Oort cloud by the giant planets. Asteroids are fragments of larger objects that were hot enought to be differentiated.

Front 42

Why are jovian planets larger than terrestrials?

Back 42

Jovian planets are larger than terrestrials because ice crystals added to the available dust, allowing larger solid objects to form, which then accreted a lot of gas. The abundant ice outside the frost line provides more material to make the cores of the giants. The cores became big enought to capture hydrogen, which turned them into gas giants.

Front 43

Why do asteroids and comets differ in composition?

Back 43

Asteroids and comets differ in composition because asteroids formed inside the frost line wile comets formed outside.

Front 44

In the condensation model for planet formation, what causes some planets to have unusual spins?

Back 44

Some planets, in the condensation model, have unusual spins because of off-center impacts of late-arriving planetesimals. The backwards spin of Venus and the unusual tilt of Uranus are assumed to have been caused by the off-center impact of one of the last big pieces to arrive.

Front 45

Jupiter and its moons are often compared to the Sun and its planets. What are some similarities between Jupiter's moon system and the solar system?

Back 45

The densities of Jupiter's moons are correlated with their distance from the planet, the main moons orbit in the same sense as Jupiter rotates, Jupiter is much larger than any of its moons, and the main moos orbit in Jupiter's equitorial plane.

Front 46

Which statements help us guess towards the origin of Neptune's moon Triton?

Back 46

Triton orbits Neptune in the opposite direction to the planet's rotation, we believe it is similar in size and density to many other Kuiper belt objects, it seems likely that it was caputred by Neptune from a passing binary Kuiper belt object, and it is much larger than any other moon of either Uranus or Neptune.

Front 47

What is the most surprising result from searches for planets orbiting around other stars?

Back 47

What is surprising is that many planets orbiting around other stars are giant planets clase to the star.

Front 48

Astronomers give mass estimates for the planets found around other stars. What information do they use to compute these estimates?

Back 48

Astronomers use the magnitude and period of the speed changes they observe to estimate the masses. The star is moving in response to the gravitational tug from the orbiting planet. The period gives the size of the orbit and the speed variations give the strength of the gravitational force from the planet.

Front 49

20 years ago, we assumed that planets around other stars were formed in similar way to our own system of planets. What property of planets subsequently found around other stars has caused the biggest problem for the theory of planet formation?

Back 49

The biggest problem for the theory of planet formation is that many extra-solar planets are gas giants orbiting close to the star.

Front 50

When can an atom not emit a photon?

Back 50

An atom cannot emit a photon when it is in the ground state.

Front 51

The spectrum of visible light from an object is almost continuous with a number of absorption lines. What could this object be?

Back 51

This object could be a star surrounded by cool, low-density gas.

Front 52

What are the two most abundant elements in the Sun?

Back 52

The two most abundant elements in the Sun are hydrogen and helium.

Front 53

What are the factors affecting nuclear fusion reactions?

Back 53

The particles must be part of a very hot gas or plasma, reactions occur more rapidly when the density is high, two protons must approach each other at high speed, and reaction will occur only in a "head-on" collision.

Front 54

What have studies of sunquakes, or heliosiesmology, revealed?

Back 54

Heleioseiesmology has revealed that our mathematical models of the solar interior are fairly accurate.

Front 55

What are some statements about neutrinos?

Back 55

Neutrinos: Large numbers of neutrinos from the Sun pass through your body every second; neutrinos are created as a by-product of energy generation in the Sun; neutrinos pass through large quantities of everything, making them very difficult to detect; neutrinos have no electric charge.

Front 56

Why is the interior of the Earth still hot?

Back 56

The interior of the Earth is hot because radioactive heating has kept it hot since it formed.

Front 57

What are some statements about plate tectonics?

Back 57

Plates are destroyed at subduction zones; plates are created at mid-ocean ridges; the Earth's lithosphere is broken into plates; most earthquakes occur at plate boundries.

Front 58

How do we know that the Earth has a liquid core?

Back 58

We know that the Earth has a liquid core because Seismic shear (S) waves cannot pass through the core.

Front 59

How have scientists mapped Venus's surface, primarily?

Back 59

Venus' surface has been mapped primarily by radar.

Front 60

In principle, which of the terrestrial worlds in our solar system should have the highest level of volcanic activity today?

Back 60

In principle, the largest terrestrial worlds in our solar system should have the highest level of volcanic activity today.

Front 61

Where has most of the oxygen in the Earth's atmosphere today come from?

Back 61

Most of the oxygen in the Earth's atmosphere today came from photosynthesis by plants.

Front 62

What are three of the principle gases, in decreasing order of abundance, in the Earth's atmosphere today?

Back 62

Three of the principle gases, in decreasing order of abundance, in the Earth's atmosphere today are nitrogen, oxygen and carbon dioxide.

Front 63

What are greenhouse gases?

Back 63

Greenhouse gases are gases which absorb infrared light.

Front 64

What is true about the atmospheres of Venus and Earth?

Back 64

Their early atmospheres were probably quite similar in size and composition.

Front 65

What is one geological process that has altered the surface of Mercury, but not that of the moon?

Back 65

A geological process that has altered the surface of Mercury, but not that of the MOon is thrust faulting that produced cliffs (scarps).

Front 66

What is one statement about volcanoes on Mars?

Back 66

Volcanoes on Mars are the largest in the solar system.

Front 67

The Earth's Moon orbits about every 27 days. Saturn's moon Dione is about the same distance from Saturn as the Moon is from Earth but has an orbital period of 2.7 days. What does this tell us about Saturn?

Back 67

This tells us that Saturn is more massive than Earth.

Front 68

Why does Jupiter have several distinct cloud layers?

Back 68

Jupiter has several distinct cloud layers because the different layers represent clouds made of different materials that condense at different temperatures.

Front 69

How do we know that Jupiter's interior is mostly hydrogen?

Back 69

Jupiter's interior must be mostly hydrogen because Jupiter has a low average density.

Front 70

How do we know that Jupiter's extra internal heat is not generated by the decay of radioactive elements?

Back 70

We know that Jupiter's extra internal heat is not generated by the decay of radioactive elements because Jupiter contains too small a fraction of heavy radioactive elements.

Front 71

Why are different mechanisms required to account for the excess heat radiated y Jupiter and Saturn?

Back 71

Different mechanisms are required to account for the excess heat radiated by Jupiter and Saturn because Saturn has finished cooling from its original contraction.

Front 72

Why are Saturn's cloud decks less colorful than Jupiter's?

Back 72

Saturn's cloud decks are less colorful than Jupiter's because Saturn's cloud decks lie deeper and are overlayed by a haze.

Front 73

Uranus and Neptune are denser than Saturn, but less dense than Earth. What does this tell us?

Back 73

This tells us that Uranus and Neptune have relatively larger rocky cores than does Saturn.

Front 74

Pluto and its moon Charon repeatedly eclipsed each other for a few years, as seen from Earth. What do studies of these eclipses help us to determine?

Back 74

Studies of these eclipses helped us to determine the radii and densities of both Pluto and Charon.

Front 75

Jupiter and its moons are often compared to the Sun and its planets. What is one reason for this?

Back 75

One reason that Jupiter and its moons are often compared to the Sun and its planets is because the main moons have nearly circular oribts in the plane of Jupiter's equator.

Front 76

Why do the surfaces of the main moons of Jupiter seem to have different ages?

Back 76

The surfaces of the main moons of Jupiter seem to have different ages because the material from the interior of each moon refreshes the surfaces at different rates.

Front 77

What are the mid-size to large moons of the giant planets composed of mostly?

Back 77

The mid-size to large moons of the giant planets are composed mostly of ice.

Front 78

What are some statements about Saturn's giant moon Titan?

Back 78

Saturn's giant moon Titan: The most abundant gas in the atmosphere is nitrogen; the Sun's ultraviolet light causes complex molecules to form; the upper atmosphere contains a thin smog; it may have an ocean of liquid ethane.

Front 79

What are Saturn's rings composed of mainly?

Back 79

Saturn's rings are composed mainly of dirty ice.

Front 80

What aspect of planetary rings do astronomers resort to guesswork over?

Back 80

Astronomers do not know how the ring systems formed. However, astronomers do know why the ring particles do not coagulate to form a few small moons, why some rings are broad with gaps and others are narrow, and how the rings stay so flat.

Front 81

Why is the planet Pluto often compared to Neptune's large moon Triton?

Back 81

Pluto is often compared to Neptune's large moon Triton becasue they are of similar size and mass.

Front 82

What are some statements about sunspots?

Back 82

The number of sunspots peaks about every 11 years; sunspots occur in pairs with opposing magnetic polarity, records of sunspot activity have been kept for about 300 years; a full sunspot cycle lasts about 22 years.

Front 83

What are solar prominences?

Back 83

Solar prominences are arch-like features in the SUn's magnetic field which are laden with gas.

Front 84

What does the term solar wind refer to?

Back 84

The term solar wind refers to the flow of particles off the outer layes of the Sun into interplanetary space.

Front 85

What is thought to be the reason that the Earth has the strongest magnetic field among the terrestrial worlds?

Back 85

It is thought that the Earth has the strongest magnetic field among the terrestrial worlds because it is the only one that has both a partially molten, metallic core and reasonably rapid rotation.

Front 86

How is Jupiter's strong magnetic field thought to be generated?

Back 86

Jupiter's strong magnetic field is thought to be generated by the dyname mechanism in a metallic hydrogen layer.

Front 87

The magnetic fields of Uranus of Neptune...?

Back 87

The magnetic fields of Uranus and Neptune are centered on a point far from the geometric enter of the planet.

Front 88

The size and compostion of Mars's moons is most similar to...?

Back 88

The size and composition of Mars's moons is most similar to a typical asteroid.

Front 89

Why do asteroids and comets differ in composition?

Back 89

Asteroids and comets differ in composition because asteroids formed inside the frost line while comets formed outside.

Front 90

Which part of a comet points most directly away from the Sun?

Back 90

The plasma (ion) tail of a comet points most directly away from the Sun.

Front 91

Where do we believe the comets now in the Oort cloud formed?

Back 91

We believe the comets now in the Oort cloud formed near the giant planets.

Front 92

The most common form of meteorite is an inhomogeneous mixture of grains of various types - type of material called chondrite. What are these meteorites believed to be?

Back 92

These meteroites made of chondrite are believed to be fragments of rock which have been free flying since the formation of the solar system.

Front 93

What is a typical shooting star in a meteor shower caused by?

Back 93

A typical shooting star in a meteor shower is caused by a pea-size particle from a comet.

Front 94

Processed meteorites with high metal content probably are ...?

Back 94

Processed meteorites with high metal content probably are fragments of a larger asteroid that was shattered by collision.

Front 95

The condensation model for the formation of the solar system postulates a rotating disk of gas and dust. One of the principal strengths of this model is...?

Back 95

One of the principal strengths of the condensation model for the formation of the solar system is that it accounts for the pattern of oribts of the planets about the Sun.

Front 96

The condensation model for the formation of the solar system accounts for the unusual spins of Venus and Uranus by ...?

Back 96

The condensation model for the formation of the solar system accounts for the unusual spins of Venus and Uranus by random off-center impacts by large planetesimals.

Front 97

What is the reason astronomers believe that no planet formed in the asteroid belt?

Back 97

Astronomers believe that no planet formed in the asteroid belt because gravitational tugs from Jupiter halted the growth of a planet and initiated destructive collisions.

Front 98

We can rule out that the Earth and Moon formed about the same time by the similar processes because ...?

Back 98

We can rule out that the Earth and Moon ofrmed about the same time by similar processes because they have different densities.

Front 99

What do you understand by the phrase habitable zone?

Back 99

The phrase habitable zone describes the range of distances from a star where liquid water could be found on a planet.