Astronomy Exam 2
By which collective name (after their discoverer) are the four major moons of Jupiter known?
"Galilean," after Galileo.
A core of rock and metal seems to be characteristic of:
All the planets.
The value of albedo is always within what range?
Always between zero and one.
The word albedo refers to the:
Amount of light reflected by a planet or other object.
The major planet whose spin axis lies almost in its orbital plane is:
Uranus
Which planet is the hottest one in the solar system, measured at the surface?
Venus.
What is a plutoid?
Any object beyond the orbit of Neptune that has enough mass to assume a spherical shape.
What is a plutino?
Any object in the same orbit as Pluto
Where was all the hydrogen in the universe formed?
In the Big Bang, at the very beginning of the universe
Which feature has been found on Mercury, but not on the Moon?
Volcanic craters
What are the three "common" substances that are believed to be important in planet formation?
Rock, ices, and gas
What is the diameter of the Moon compared with the diameter of Earth?
about 1/4 of the diameter of Earth.
What is the overall composition of the outer atmospheric regions of Jupiter in terms of the relative numbers of atoms?
86% hydrogen, 13% helium, and 1% everything else.
The surface temperature of Titan, the largest moon of Saturn, is:
95 K (-178°C).
The magnetic field strength at Jupiter's "surface" exceeds that at Earth's equatorial surface by a factor of about:
14.
The African and South American continents are separating at a rate of about 3 cm per year, according to the ideas of plate tectonics. If they are now 5000 km apart and have moved at a constant speed over this time, how long is it since they were in contact?
170 million years.
The first successful Moon landing, by Apollo 11, placed astronauts on the Moon in:
1969.
Exoplanets were first observed in:
1992.
How many large, spherical moons are in orbit around Jupiter?
4.
Jupiter's mass makes up what fraction of the total mass of the planetary system, excluding the Sun?
70%
How much more massive would Jupiter need to be to generate energy by nuclear fusion in its interior?
75 times more massive.
The major constituents of Earth's atmosphere are:
77% nitrogen and 21% oxygen.
In the solar system, what is the snow line?
A boundary in the solar system such that ices of water, carbon dioxide, methane, and ammonia are found only outside of this line (i.e., farther from the Sun)
The material from which our solar system formed is believed to be:
A cold, dark cloud of gas and dust.
What is a protoplanetary disk?
A disk of gas and dust, such as those observed around some stars in the Orion nebula.
The Kuiper belt is:
A flat or donut-shaped distribution of distant comets around the Sun, extending out about 500 AU.
The conditions on the surface of Venus are:
A high-pressure, high-temperature, carbon dioxide atmosphere.
What is a "mare" (plural: "maria") on the Moon?
A large area of darker material on the lunar surface, formed by ancient lava floodplains.
What is the Great Red Spot on Jupiter?
A large, long-lived anticyclonic storm that is maintained by the differential rotation of Jupiter's atmosphere.
Jupiter's satellite Europa is believed to be made up of:
A metallic core and a rocky mantle covered with a liquid water ocean whose surface is frozen.
What is a Martian dust devil?
A natural whirlwind on the planet's surface.
What was the material from which the solar system formed?
A nebula made mostly of hydrogen and helium gas but enriched in heavier elements from supernova explosions.
An asteroid is:
A planetesimal moving in an orbit around the Sun.
The physical structure of Saturn's rings is:
A sequence of many thousands of separate ringlets consisting of ice blocks and ice-coated rock.
Which object might be classified as a small solar system body?
A small asteroid.
The Oort cloud is:
A spherical distribution of distant comets around the Sun, extending out about 50,000 AU.
To what does the name Pangaea refer?
A supercontinent on a tectonic plate that split into the present North and South America, Europe, and Africa
Neptune's predominantly blue appearance is caused by:
Absorption of the red end of the spectrum of reflected sunlight by the methane in its atmosphere.
The main reason for the very high temperature (750 K) on the surface of the planet Venus is thought to be:
Absorption of visible radiation by the Venusian surface and the subsequent trapping of infrared radiation emitted by the surface by the atmosphere and clouds.
The manner in which the large, outer planets formed in our solar system was MOST likely the:
Accretion of planetesimals to form a core, followed by the gravitational capture of hydrogen and helium gas.
The formation of terrestrial-type planets around a star is MOST likely to have occurred through what process?
Accretion, or slow accumulation of smaller particles by mutual gravitational attraction
Which feature has NOT been seen or detected on Mars?
Active volcanoes
Rings of dust and icy particles are found around which planets?
All four of the giant planets.
If the greenhouse gases in a planet's atmosphere are reduced, the planet will:
Become cooler.
The dark, reddish bands on Jupiter are called
Belts.
Where is the mantle of Earth located?
Between the core and the crust
The large amount of free oxygen in Earth's present atmosphere is primarily a result of:
Biological processes such as photosynthesis.
What is the visual appearance of Uranus from space?
Blue-green and featureless.
What is the visual appearance of Neptune from space?
Blue-green with white, high-altitude clouds and dark storms.
Which statement about the similarities of Mercury and our Moon is NOT true?
Both Mercury and the Moon have large, circular, and relatively flat basins, or maria, on parts of their surfaces.
How was Neptune discovered?
By a careful application of Newton's laws to the somewhat irregular motions of Uranus
How was the dwarf planet Pluto discovered?
By searching photographs of the sky for an object that moved against the background of distant stars
The main gases contributing to the greenhouse effect are:
CO2 and H2O.
What were the dominant gases in Earth's second atmosphere?
Carbon dioxide and nitrogen.
The "snow" that occasionally falls in and near the polar regions of Mars consists of:
Carbon dioxide ice
What is the MAIN reason that the greenhouse effect has been much more effective in raising the surface temperature on Venus than in raising the surface temperature on Earth?
Carbon dioxide, which traps heat from the planet's surface, is the major component in the very dense Venusian atmosphere, while it is a only a minor constituent of Earth's.
What is the LARGEST known asteroid in our solar system?
Ceres.
"Continental drift" (the idea that tectonic plates drift around on Earth's surface) is now thought to be caused by:
Circulation currents in the deep interior (known as convection), causing slabs of Earth's crust to move slowly.
The major gaps in the rings of Saturn are MOST likely to be caused by:
Combined gravitational forces from Saturn and its moons that deflect the paths of particles that stray into the gaps.
The major difference between the orbital paths of comets that we see in the inner solar system and those of the asteroids in the asteroid belt is that:
Cometary orbits are highly elliptical and at random inclinations to the ecliptic plane compared with the circular orbits of asteroids in the ecliptic plane.
What is the basic difference between comets and asteroids?
Comets are mostly composed of ices, whereas asteroids are mainly composed of rocks.
The first satellite discovered in orbit about Pluto was Charon. What is unusual about this moon?
Compared with planet-satellite systems in the rest of the solar system, Charon is very large and very close to Pluto.
The birthplace of the Sun and planets (and of other stars and maybe their planets) is thought to have been in:
Cool gas and dust clouds.
Which process has played the greatest role in shaping the surface of the Moon?
Impacts of interplanetary bodies of all sizes, producing many craters.
Where in the universe are heavy elements with masses greater than that of helium being produced at this time?
In the central cores of stars.
Pluto is in a 2:3 resonance orbit with Neptune. What does this mean?
During the time that Neptune orbits the Sun three times, Pluto orbits it twice.
Accretion is the process by which:
Dust grains and ice crystals coalesce to form planetesimals.
How does the dust tail of a comet compare with its gas (ion) tail?
Dust tails are more massive than gas tails.
An object in the solar system orbits the Sun and has enough mass that its gravity has pulled it into a spherical shape, but it does not have enough gravity to clear its neighborhood of orbiting debris. This object is classified as a(n):
Dwarf planet.
What is the difference between a chemical reaction and a nuclear reaction (such as fusion)?
In a chemical reaction the atoms don't change, but separate or come together to form new molecules. In a nuclear reaction atoms change into new elements because their nucleus is changed.
Which statement about the Moon is TRUE?
Earth can never be seen from one side of the Moon.
The habitable zone in our own solar system encompasses:
Earth only.
Earth has an average density of 5500 kg/m3, although the density of rock on its surface is about 3000 kg/m3. What conclusion can be reached about Earth s core from this observation?
Earth's core is made of material far denser than surface rock.
The LARGEST of the terrestrial planets is:
Earth.
The planet with the greatest mean density is:
Earth.
MOST of the planets orbit the Sun on or close to the:
Ecliptic plane.
Fusion is the process by which:
Elements are transformed into heavier elements by nuclear reactions.
Which process was NOT important in helping to remove carbon dioxide from Earth's early atmosphere?
Escape of carbon dioxide into space.
Most of the elements beyond hydrogen and helium in the periodic table in the Sun and the solar system MOST PROBABLY originated in:
Fusion reactions in the centers of earlier stars.
One particularly important collision in the early inner solar system about 100 million years after Earth's formation resulted in the:
Formation of our Moon.
What are the main characteristics of our solar system?
Four small planets close to the Sun and four large planets far from the Sun
How were the first rings of Uranus discovered?
From Earth, when each ring momentarily blocked the light from a background star.
The MOST massive moon in the solar system is:
Ganymede
Compared with Earth, Jupiter, and Saturn, the magnetic fields of Uranus and Neptune:
Have axes that are tilted a long way from the spin axis of the planets.
Auroras on Earth are caused by:
High-energy charged particles from the magnetosphere guided by Earth's magnetic field into polar regions of the atmosphere.
Which clause CORRECTLY describes the mantle of Earth?
Hot, semimolten rock that flows upward in hotter parts of the mantle and downward in cooler parts
MOST of the mass of the universe (about 98%) is in the form of:
Hydrogen and helium
Why did Earth's earliest atmosphere, composed primarily of hydrogen and helium, not last long?
Hydrogen and helium are light gases, and they soon escaped into space.
What is thought to be the physical mechanism that was responsible for the present mix of chemical elements in the universe?
Hydrogen and helium were formed in the Big Bang, whereas the heavier elements were made in the centers of stars.
What were the dominant gases in Earth's earliest atmosphere after it first formed?
Hydrogen and helium.
What is the composition of Jupiter's clouds?
Ice crystals of methane, ammonia, and water
What is the Jeans instability?
If a cloud of gas and dust is sufficiently dense, it will collapse due to its own gravity.
The rings of Saturn are seen by:
Reflected and scattered sunlight.
Sunlight reaches Earth's surface, is absorbed, and re-radiates as:
Infrared radiation.
The distinctive red color of Mars is probably caused by
Iron oxides or rust in the soil.
The moons of Mars are:
Irregularly shaped, cratered, and grooved.
Where did the majority of the large amount of carbon dioxide (CO2) from the second major atmosphere to form on the early Earth end up?
It dissolved in the oceans, then was absorbed into the shells of living creatures, ultimately turning into the limestone of many mountain ranges.
Water was once much more abundant on Venus than it is now. Where did this ancient water go?
It evaporated into space.
What causes Io to be so active geologically?
It is in a very circular orbit, but it is subjected to tidal flexing from Jupiter because of orbital perturbations from the other Galilean satellites.
Saturn's moon Titan is different from all other moons of the planets because:
It possesses a thick atmosphere.
Suppose that observers using the Hubble Space Telescope detect around several solar-type stars the presence of planets with the following characteristics: low density, large size, fluid surfaces, rapid rotation. How would these planets be classified in terms of our solar system?
Jovian planets (i.e. Jupiter-like)
In the Nice model of solar system formation:
Jupiter and Saturn formed first, followed by Uranus and Neptune.
According to current theories of planetary formation, why is Saturn less massive than Jupiter?
Jupiter formed first.
Why does no major planet orbit the Sun at the location of the asteroid belt?
Jupiter's gravitational pull stirred up the planetesimals, preventing them from coalescing into a single large object.
In our solar system, which planet is NOT a member of the terrestrial group?
Jupiter.
Which planet in our solar system has the LARGEST mass?
Jupiter.
In its orbit around Earth, the Moon:
Keeps the same side toward Earth.
The MOST likely origin of the "dirty snowballs" that become comets when they are deflected into orbits that bring them closer to the Sun is the:
Kuiper belt and Oort cloud surrounding the solar system.
Atmospheric pressure at the surface of Mars compared with atmospheric pressure at the Earth's surface is:
Less than 1/100
What are the physical characteristics of the "other" (non-Galilean) moons of Jupiter?
Less than 300 km in diameter and irregular in shape.
What characteristic features are seen on the visible surface of Jupiter?
Light and dark bands parallel to the equator.
The atmosphere of the gas-giant planet HD 209458b is believed to contain hydrogen, sodium, oxygen, carbon, and carbon monoxide. Where does this information come from?
Light shines through the planet's atmosphere when it passes in front of its star, so a spectrum can be taken.
In what form is the hydrogen in Jupiter's interior?
Liquid metallic hydrogen, electrically conducting
What type of search technique (known as the "transit method") has discovered the largest number of exoplanets?
Looking for small variations in the light of a distant star indicating motion of a planet across the face of the star.
Most of the asteroids of the solar system move around the Sun between the orbits of which planets?
Mars and Jupiter.
The asteroid belt exists between the orbits of which planets?
Mars and Jupiter.
Which statement is TRUE for Mars?
Mars has dry riverbeds but no liquid water on its surface at the present time.
Mars' atmosphere contains no water vapor. Why is this?
Mars' gravity is too weak to retain water vapor on the planet.
Phobos and Deimos are moons of which planet?
Mars.
A global magnetic field generated from inside the planet is found around which terrestrial planet or planets?
Mercury and Earth.
Which planets do NOT have any natural satellites (i.e. moons)?
Mercury and Venus.
The albedo of Mercury is about 0.1. This means that:
Mercury reflects 1/10 of the sunlight falling on it.
The CORRECT sequence of planets in our solar system from the Sun outward is:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
The correct sequence of planets in our solar system from the Sun outward is:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
The SMALLEST of the terrestrial planets is:
Mercury.
The SMALLEST terrestrial planet is:
Mercury.
The planetary orbit of which planet is the least circular (and is more clearly an ellipse)?
Mercury.
The planetary orbit with the GREATEST inclination to the plane of the ecliptic is the orbit of
Mercury.
The smallest planet in our solar system is:
Mercury.
Ozone is a gas consisting of:
Molecules containing three oxygen atoms.
The internal structure of Earth is a:
Molten iron inner core, solid iron outer core, surrounded by a thick, flexible mantle of rock.
How many moons are now known to orbit Jupiter?
More than 60.
What fraction of the mass of Earth is made up of the elements hydrogen and helium?
Much less than 1%
The ice giants are:
Neptune and Uranus
What is the relationship between Earth's mantle and crust?
New crust is formed by magma rising from the mantle in some places, and old crust is pushed back down into the mantle in other places.
The solar system formed about how long after the Big Bang?
Nine billion years.
Venus has:
No magnetic field at all.
The rotation period of Jupiter is:
Relatively short, on the order of 10 hours.
The MOST probable process for the formation or acquisition of the planets of the Sun is the:
Relatively slow growth of smaller objects by collisions and mutual gravitational attraction.
The composition of a typical asteroid is:
Rock and metal.
An atmosphere containing a significant amount of oxygen is found around which terrestrial planet or planets?
Only Earth.
The region at the farthest limits of the solar system in which a large number of objects composed of rock and ice circle the Sun in a roughly spherical region is called the:
Oort comet cloud.
According to our present theory of solar system formation, where were the four inner planets formed?
Our present theory has no clear answer to this question.
Tomorrow's weather report for Venus would be:
Overcast and very hot.
Only three elements are believed to have formed directly in the Big Bang. These elements do NOT include:
Oxygen
Photosynthesis in plants on Earth maintains a balance between which of the two atmospheric gases?
Oxygen and carbon dioxide.
Ozone in the stratosphere performs an important task that protects life on Earth. What is it?
Ozone absorbs much of the dangerous solar ultraviolet light.
MOST comet nuclei are believed to be:
Pieces of dusty ice left over from the formation of the solar system.
Craters are not apparent on Earth at the present time in the abundance seen on the Moon because:
Plate tectonics has returned cratered surface layers into Earth's interior, and weathering has obliterated the more recent craters.
A comet's tail always:
Points away from the Sun, regardless of the motion of the comet.
The asteroid belt is made up of:
Rocky bodies with diameters ranging from less than a kilometer to hundreds of kilometers.
What is the basic structure of the planet Jupiter?
Rocky core, liquid hydrogen mantle, gaseous atmosphere
What is the interior structure of Saturn?
Rocky core, thick mantle of liquid metallic hydrogen and helium, relatively thin gaseous atmosphere
Which planet has wide, bright rings that are easily visible from Earth?
Saturn
Which planet in our solar system has the lowest average density?
Saturn.
In searches for planets orbiting stars other than the Sun, what is the astrometric method?
Searching for tiny wobbles in the position of a star, due to the gravitational pull of a planet orbiting around it.
A few of the largest asteroids appear to be spherical. How do you think they got this way?
Self-gravity was sufficient to pull the largest asteroids into a spherical shape during their early history.
The mass of the solar nebula that began contracting to form the solar system was estimated to be:
Several solar masses.
To what does planetary differentiation refer?
Sinking of heavier elements toward the center of a planet and the floating of lighter elements toward the surface
How many times have humans landed on the Moon?
Six times.
What is the difference between an asteroid and a meteoroid?
Size: Asteroids are larger, and meteoroids are smaller.
The overall shape of the orbits of MOST of the planets in the solar system is:
Slightly elliptical, but nearly circular.
Compared with the density of liquid water (1000 kg/m3), the average density of the outer giant planets is:
Slightly higher, about 1.2 times.
The early phases of planetary formation into protoplanets were characterized by the:
Slow accretion of small particles by gravitational attraction and collision.
The process of accretion in planetary formation is the:
Slow accumulation of solid particles by gravity and collision into larger, solid objects.
Each of the following characteristics is included in the formal definition of a planet EXCEPT ONE. Which is the exception?
Spins fast enough to produce its own magnetic field.
The MOST likely mechanism for the solar system is that the:
Sun and planets slowly condensed to their present form from a gas and dust cloud.
Suppose the Hubble Space Telescope discovers a series of planets with the following characteristics moving around a star that resembles our Sun: spherical, solid surfaces; mean densities about four times that of water; radii about 4000 km; low-density atmospheres. How would these planets be classified in comparison with our solar system?
Terrestrial planets (i.e. Earth-like)
Suppose the Hubble Space Telescope discovers a series of planets with the following characteristics moving around a star that resembles our Sun: spherical, solid surfaces; mean densities about four times that of water; radii about 4000 km; low- density atmospheres. How would these planets be classified in comparison with our solar system?
Terrestrial planets (i.e. planets like Earth)
How has the CO2 concentration in Earth s atmosphere changed over the past thousand years?
The CO2 concentration was relatively constant for about 800 years but has increased significantly since A.D. 1800.
Which statement is the BEST explanation for the origin of the Moon?
The Moon was created by the process described in (C), except that the ejection was caused by the impact of some large object on Earth.
As the forming planet Jupiter moved through the early outer solar system, it collided with huge numbers of gas and dust particles there. What effect did this have?
The additional mass made the young Jupiter move more slowly, giving it less energy and causing it to migrate inward.
What happened to the first major atmosphere to develop on the early Earth, which consisted of hydrogen and helium?
The atmosphere drifted off into space as Earth s gravity was too weak to hold the light molecules of hydrogen and helium.
In which way are Venus and Mars alike and yet both markedly different from Earth?
The atmospheres of Venus and Mars are both made up primarily of carbon dioxide.
What is the Kuiper belt?
The relatively flat distribution of objects in the plane of the ecliptic, extending from around the orbit of Pluto out to about 50 AU from the Sun
What is the origin of many of the bodies in the Kuiper belt and the Oort comet cloud?
The gravitational forces from Jupiter and Saturn flung planetesimals from regions closer to the Sun out into these regions.
Compared with Jupiter and Saturn, Uranus and Neptune contain proportionally more heavy materials, more ices, and less hydrogen. How do we account for this?
The heavy materials are from asteroids flung outward by the inward migration of the gas planets, the ices are from icy masses that had spiraled in from far out in the solar system, and the deficit of hydrogen was caused by the prior formation of the gas planets.
There is very little hydrogen or helium in the inner part of the solar system today. We believe the reason for this is that:
The intense radiation from the early Sun drove the light elements out of the inner solar system.
The large, outer planets have high masses and hence generate powerful gravitational fields, and yet they have low average densities. What does this indicate about their interiors?
The interiors are composed mainly of very light elements, such as hydrogen and helium.
What is the lunar regolith?
The layer of fine powder covering the lunar surface
Which physical feature of the planet Mercury causes the deflection of solar wind particles away from its surface?
The magnetic field that, like Earth's, produces a magnetosphere surrounding the planet.
What is the current status of Earth's ozone layer?
The ozone layer has been somewhat depleted, but if left alone, it could restore itself in a century.
Which characteristic is NOT typical of our planetary system?
The physical size of most of the planets is about the same.
Most of the satellites of Uranus orbit the planet in:
The plane of the planet's equator and therefore in a plane almost at right angles to the ecliptic.
In order for an exoplanet to be capable of sustaining life, all of the following situations would have to be true EXCEPT ONE. Which is the exception?
The planet would have to be in a solar system containing a giant planet in a highly eccentric orbit.
Why is it that terrestrial planets are thought to have dense iron cores?
The planets were molten early in their life, and the heavy elements sank and lighter materials floated to the surface (planetary differentiation).
All the boundaries of the major interacting tectonic plates on Earth's surface are coincident with:
The positions of maximum earthquake occurrence.
What name is given to the concentration of mass that formed at the center of the solar nebula and eventually became the Sun?
The protosun
The solar system formed about 4.5 billion years ago. What has been the rate of bombardment by space debris in the inner part of the solar system since then?
The rate decreased steadily for about 400 million years after the solar system's creation. Then a very heavy bombardment began and lasted about 300 million years. The rate has been greatly reduced since then.
What process heated the early solar nebula as it slowly condensed toward a central protosun?
The release of heat by collisions of particles as they gained kinetic energy in falling toward the center of the nebula.
What is a planetary nebula?
The result of a relatively gentle stellar outburst in which matter is ejected into space.
Saturn is less massive than Jupiter but almost the same size. Explain.
The smaller mass exerts less gravitational force and is unable to compress the mass as much as in Jupiter.
The Earth's magnetic field protects Earth and its inhabitants from:
The solar wind, which would otherwise irradiate and damage life-forms if not deflected.
Which statement is NOT true about asteroids and the asteroid belt?
The total number of asteroids is between 10,000 and 12,000.
In which layer of Earth's atmosphere does weather occur?
The troposphere.
Which scientific approach gives us the MOST information about the deep interior of Earth?
The worldwide measurement of low-frequency seismic waves produced by earthquakes
How are space probes to the outer planets such as Jupiter protected from being obliterated by collisions with asteroids in the asteroid belt?
They aren't. Asteroids are so far apart that the spacecraft just sail through.
The atmosphere that we are now breathing is the _____ atmosphere Earth has had.
Third.
What are the major layers of Earth's atmosphere in the CORRECT order from the surface upward?
Troposphere, stratosphere, mesosphere, thermosphere.
What are the Van Allen belts?
Two doughnut-shaped regions of high-energy charged particles in Earth's magnetosphere.
What causes the banded structure on Jupiter's visible "surface" as seen from Earth?
Underlying rising and falling convection pattern stretched into bands by Jupiter's rapid rotation
The relatively large amount of water found on Earth is believed to have come from:
Water-rich comets.
How do we measure the mass of an extrasolar planet?
We use Newton's law of gravity, using the measured distance of the planet from its star and the planet's gravitational pull on the star.
At what point in time do we say that the protosun became the Sun?
When thermonuclear fusion reactions began at its center.
What are the light-colored bands on Jupiter called?
Zones.
Moons have been discovered around:
all the planets except those nearer to the Sun than Earth is.
Approximately how many planets are believed to exist in our Galaxy?
at least 100 billion.