Astronomy Test 2: The Solar System
To observe a planet executing retrograde motion, you must watch the planet for many successive Select one: A. minutes. B. hours. C. weeks. D. years.
Weeks
Consider a planet as it moves in prograde motion. Over the course of several nights, how will the planet appear to move relative to the background stars? Select one: A. East to west B. It will move randomly, as planets move differently than the stars C. West to east D. It will not move at all, as planets do not move with the stars
West to east
The more massive Earth exerts a gravitational force on the Moon. Does the less massive Moon exert a gravitational force on the Earth? Select one: Yes, and it is equal Yes, but it is less Yes, but it is greater No, the Moon has no gravity
Yes, and it is equal
Was it possible for the geocentric system of Ptolemy to explain the observed retrograde motion of the planets? Select one: A. No, because it was not in use long enough to make such predictions B. Yes, through a system of epicycles and deferents C. No, because observations of this retrograde motion were not known to the ancients Incorrect D. Yes, assuming that some planets orbited the Sun while others orbited Earth E. No, because it was not able to predict retrograde motion
Yes, through a system of epicycles and deferents
Imagine you're lucky enough to come across a meteorite immediately after it passed through Earth's atmosphere. Is it safe to pick it up? Select one: No. It's radioactive. No. It may be full of tiny aliens. Yes, but even the smallest ones are too heavy to lift. No. It will be extremely hot! Yes. It's worth a lot of money!
Yes. It's worth a lot of money!
An incandescent light (glowing tungsten filament) produces: Select one: an absorption spectrum, with dark lines due to the solid filament. a continuous spectrum. a continuous spectrum, with bright tungsten lines added. an emission spectrum, with bright lines due to tungsten. a continuous spectrum, with dark lines of tungsten and argon as well.
a continuous spectrum.
A neon light (thin hot neon gas in a sealed tube) gives us: Select one: a continuous spectrum, since the neon is hot enough to glow. a few bright emission lines, telling us the gas is neon. a continuous spectrum, with dark lines identifying the neon atoms are present. nothing visible to us, but a hot of infrared lines as heat.
a few bright emission lines, telling us the gas is neon.
The Orion Nebula is a hot, thin cloud of glowing gas, so its spectrum is: Select one: a continuum, strongest in the color red. a few bright lines against a dark background. a few dark line in the continuum. not in the visible portion of the spectrum. a continuum, but with both bright and dark lines mixed in.
a few bright lines against a dark background.
The reason astronomers use telescopes in space is because Earth's atmosphere Select one: absorbs or scatters some of the light at all wavelengths. absorbs all of the light at some wavelengths. distorts images of astronomical objects. all of the above. none of the above.
all of the above. absorbs or scatters some of the light at all wavelengths. absorbs all of the light at some wavelengths. distorts images of astronomical objects.
Which of the Jovian planets have rings? Select one: Jupiter Saturn Uranus Neptune All of them
all of them
Newton introduced the Universal Law of Gravity, and with it was able to explain Select one: all three of Kepler's laws the sequence of lunar phases. why planets moved in "retrograde loops" as seen from Earth. why no one could detect stellar parallax.
all three of Kepler's laws
Our knowledge of the composition of the Earth's core comes form Select one: analysis of the material erupted from volcanoes. analysis of earthquake waves. visits from the mole people who tell us what's going on down there. samples obtained by drilling deep holes. x-ray pictures taken with a powerful device in Russia.
analysis of earthquake waves.
Ptolemy's model for planetary motion predicts that during retrograde motion a planet will appear Select one: A. at its dimmest B. at the same brightness as it always appears C. at its brightest
at its brightest
The tail of a comet is generally directed Select one: away from the Sun because of the solar wind and pressure from the Sun's light. opposite the direction of motion as the comet passes through interplanetary matter. along the comet's magnetic field lines. toward the Sun because of the Sun's gravitational attraction.
away from the Sun because of the solar wind and pressure from the Sun's light.
Uranus is peculiar because its Select one: orbit is strongly inclined to the ecliptic plane. axis of rotation is near the ecliptic plane. radius is so large. orbit is highly eccentric
axis of rotation is near the ecliptic plane.
The greenhouse effect is caused mostly by Select one: the aurora borealis. carbon dioxide in the atmosphere. pesticides. depletion of the ozone layer.
carbon dioxide in the atmosphere
According to Newtonʹs Law of Universal Gravitation, if the Moon were three times further from Earth, the force by Earth on the Moon would Select one: increase by a factor of 3. decrease by a factor of 3. increase by a factor of 9. decrease by a factor of 9. stay the same.
decrease by a factor of 9.
Why does Ptolemy's model for planetary motion predict that during retrograde motion a planet appear at its brightest? Select one: A. during retrograde motion planets appear smaller in the night sky. B. planets always appear the same brightness in the night sky regardless of their apparent motion. C. during retrograde motion the planet is closest to Earth. D. during retrograde motion planets appear larger in the night sky. E. during retrograde motion the planet is farthest from Earth.
during retrograde motion the planet is closest to Earth.
The main reason astronomers use large telescopes is that large telescopes Select one: gather more light. have a larger magnification. have a bigger field of view. none of the above. all of the above.
gather more light
A moon covered with numerous and very old craters created by meteorite impacts likely Select one: has no protective magnetic field. has a cold, solid interior. orbits a large Jupiter size planet. has no ocean to cover the craters.
has a cold, solid interior.
It's now believed that the Moon Select one: has large chunks of icy water in its polar craters. has a thick layer of permafrost below its surface. has absolutely no water. has traces of water in its shadowy regions.
has traces of water in its shadowy regions.
Without our own greenhouse effect, our Earth would: Select one: remain at exactly the same temperature it is now. have its oceans frozen, like the surface of Mars. have a much more livable atmosphere than it has now. be as hot as the surface of Venus.
have its oceans frozen, like the surface of Mars.
The primary source of erosion on the Moon is Select one: impact cratering. crust fracturing due to tectonic motion. boulders crumbling and rolling downhill. subsurface water flow. strong solar-wind bombardment.
impact cratering.
he gravitational attract between two objects ______ as the distance between the objects decreases. Select one: decreases increases stays the same
increases
The length of day is Select one: staying the same decreasing increasing because: Select one: the continents are slowly shifting. the Moon's gravitational pull on Earth's tidal bulge. of frequent impacts on Earth. nothing is strong enough to influence Earth's rotation rate. Earth is too massive.
increasing; the Moon's gravitational pull on Earth's tidal bulge.
The color of a glowing gas Select one: is a combination of the brightest emission lines. is not related to the gas' emission lines. is due solely to the brightest emission line
is a combination of the brightest emission lines.
In a heliocentric cosmology, such as the one proposed by Copernicus, retrograde motion Select one: A. is explained as a visual effect due to a Earth's rotation axis being tilted. B. is explained by having planets vary their orbital speed as they revolve around the Sun. C. is explained as a visual effect due to a faster planet passing a slower planet. D. cannot be explained.
is explained as a visual effect due to a faster planet passing a slower planet.
Why was Galileo's observation of four moons orbiting Jupiter so revolutionary? Select one: A. nobody had previously observed something move in the heavens. B. that planet is too small to have moons. C. it demonstrated that the Earth is not at the center of the solar system. D. it was the first time a telescope was used for astronomy.
it demonstrated that the Earth is not at the center of the solar system.
Halley's Comet is only visible for a short time because Select one: it's only visible when it is closest to the Sun, which is also when the comet is moving the fastest. it's only visible when it is closest to the Sun, which is also when the comet is moving the slowest. it's only visible when it is farthest from the Sun, which is also when the comet is moving the fastest. it's only visible when it is farthest from the Sun, which is also when the comet is moving the slowest.
it's only visible when it is closest to the Sun, which is also when the comet is moving the fastest.
Why does Mercury have the highest variation in orbital in orbital speed? Select one: it's closest to the Sun. it's name sounds funny. it's the most massive planet. it's orbit is the most eccentric. it's the smallest planet.
it's orbit is the most eccentric.
The change in position of the continents over time is primarily caused by Select one: mantle material circulating inside Earth. global wind patterns and sustained ocean currents. Earth's slowly shrinking as it cools. continental plates floating on the ocean.
mantle material circulating inside Earth.
The element ______ must be fluorescent lights Select one: hydrogen nitrogen neon helium mercury
mercury
If an object's spectral lines are shifted to longer wavelengths, the object is Select one: moving away from us. moving toward us. very cold. very hot.
moving away from us
The lunar highlands are known to be ______ the lunar maria Select one: the same age as older than younger than because: Select one: the highlands have less craters than the maria. the highlands contain more craters than the maria. the highlands have the about same number of craters as the maria.
older than; the highlands contain more craters than the maria.
In Kepler's model for planetary motion the Sun is located at Select one: A. on the opposite side of the ellipse from the planet. B. one of the focus points for the planet's elliptical orbit. C. at perihelion. D. at the center of the planet's elliptical orbit. E. at aphelion.
one of the focus points for the planet's elliptical orbit.
To measure the mass of the Sun using the properties of Mars, astronomers need to measure Mars' Select one: orbital period and semi-major axis. semi-major axis and mass. mass and orbital period.
orbital period and semi-major axis.
In photos of the moon, the near and far shadows don't appear to be parallel because Select one: there's a nearby spotlight just off to the left of the scene. our brain perceives them as nonparallel due to the camera's perspective. the reflection of the sunlight off the lunar surface. ALIENS!
our brain perceives them as nonparallel due to the camera's perspective.
Kepler's Second Law (equal areas in equal times) says in effect that Select one: the more remote planets (whose orbits sweep out larger areas) must orbit faster, to sweep out the whole area in a similar time. planets move faster as they near the Sun. planets move slower as they near the Sun. planets move at a steady pace about the Sun.
planets move faster as they near the Sun.
Epicycles are the circular loops that ________ make(s) during an orbit about ________. Select one: A. planets other than Earth; Earth B. Earth; the Sun C. distant stars; Earth D. planets other than Earth; the Sun
planets other than Earth; Earth
The form of electromagnetic radiation with the lowest energy is Select one: infrared light x-rays radio waves ultraviolet light gamma rays visible light
radio waves
Kepler's Third Law Select one: allowed him to predict when eclipses occur. showed that the Sun is much farther away than the Moon. allowed him to measure the distance to nearby stars. relates a body's mass to its gravitational attraction. relates a planet's orbital period to the size of its orbit.
relates a planet's orbital period to the size of its orbit.
When you observe the Moon from Earth, you always see the same side. This observation implies that the Moon Select one: rotates on its axis once a day. rotates on its axis once a month. does not rotate on its axis.
rotates on its axis once a month.
Compared to the first quarter phase, a full moon appears to be ______ as the first quarter moon. Select one: half as bright the same brightness twice as bright ten times as bright
ten times as bright
A circle has an eccentricity of Select one: 0 0.5 1.0 it depends on the size of the circle
0
Faint stars appear white because Select one: the rods found in human eyes require a lot of light to distinguish color. the cones found in human eyes require a lot of light to distinguish color. the rods found in human eyes are very sensitive to light. all faint stars are produce more white light than any other color of light.
the cones found in human eyes require a lot of light to distinguish color.
Assume that you wish to draw an ellipse with a semimajor axis of a = 12 inches and an eccentricity e = 0.5. What would be the appropriate distances for the separation of the thumbtacks? Select one: 0 inches 6 inches 12 inches 24 inches
12 inches
f a planet has a perihelion distance of 10 AU and an aphelion distance of 20 AU, what is the planet's semimajor axis length? Select one: 10 AU 15 AU 20 AU 40 AU
15 AU
Planet Bart has a semimajor axis of 12 AU while Planet Lisa, which orbits the same star, has a semimajor axis of 21 AU. When the eccentricities for the two orbits are compared its found that Select one: the eccentricities are unrelated to the sizes of the semimajor axes. Planet Bart has a smaller eccentricity because it has a smaller semimajor axis. Planet Bart has a larger eccentricity because it has a smaller semimajor axis. both planets have the same eccentricity because they orbit the same star.
the eccentricities are unrelated to the sizes of the semimajor axes.
Why does the element Mercury be fluorescent lights? Select one: the color of the fluorescent lights. the emission lines from the fluorescent lights match the lines associated with this element. the brightness of the fluorescent lights. the continuous spectrum from the fluorescent lights match the spectrum associated with this element. only this element glows when it's heated.
the emission lines from the fluorescent lights match the lines associated with this element.
When astronauts went to the Moon they were able to walk around on the Moon's surface (i.e. they didn't float off into space) because Select one: they wore heavy boots. the gravitational force from the Moon acting on the astronauts held them to the surface. they always walked on the side of the Moon that faced away from the Sun. This allowed the gravitational pull from the Sun to hold them down on the Moon's surface. astronauts never really traveled to the Moon. It was all a government conspiracy.
the gravitational force from the Moon acting on the astronauts held them to the surface.
Cosmology is the study of Select one: A. the origin and evolution of the Universe. B. beauty treatments. C. ancient models of the Solar System. D. the motion of planets.
the origin and evolution of the Universe.
Consider a planet orbiting the Sun. If the mass of the planet doubled but the planet stayed at the same orbital distance, then the planet would take Select one: more than twice as long to orbit the Sun. exactly twice as long to orbit the Sun. the same amount of time to orbit the Sun. exactly half as long to orbit the Sun. less than half as long to orbit the Sun.
the same amount of time to orbit the Sun.
The size of the Hubble Space Telescope's primary mirror was set by Select one: time constraints in due to previous shuttle disasters. technological limitations. the size of the space shuttle's cargo bay. financial constraints due to cutbacks at NASA.
the size of the space shuttle's cargo bay.
Why are radio waves the form of electromagnetic radiation with the lowest energy? Select one: this form of radiation has the highest frequency. this form of radiation moves the fastest. this form of radiation moves the slowest. this form of radiation has the lowest frequency.
this form of radiation has the lowest frequency.
Kepler's Laws apply Select one: to all objects in an orbit. only to the eight planets orbiting about our Sun. only to planets orbiting about stars.
to all objects in an orbit.
The general heliocentric approach of Copernicus won favor among astronomers primarily because it Select one: A.placed the Earth at the center of the heavens. B.explained why we do not feel the Earth move. C.was more aesthetically pleasing than the old model. D.made more accurate predictions than the Ptolemaic model.
was more aesthetically pleasing than the old model.
Which of the following techniques is not used to improving seeing? Select one: Adding together images from multiple telescopes separated by large distances Placing telescopes in space, above most of Earth's atmosphere Making small changes to the shape of telescope's primary mirror Adding up many short exposure images of the same object
Adding together images from multiple telescopes separated by large distances
On which of these assumptions do Ptolemy and Copernicus agree? Select one: A. Earth must be the center of all motion in the Cosmos B. The Sun must orbit us, but the planets do orbit the Sun C. Venus must always stay between Earth and the Sun D. The Sun was bigger than Earth E. All orbits must be perfect circles
All orbits must be perfect circles
Imagine that you are the head of a funding agency that can afford to build one telescope. Which of the following proposed telescopes would be best to support? Select one: A radio telescope in orbit around Earth An X-ray telescope located in New Mexico An ultraviolet telescope in orbit around Earth
An ultraviolet telescope in orbit around Earth
For a wave of constant velocity, like an electromagnetic wave, how are the wavelength and frequency related? Select one: As the wavelength goes up, the frequency goes down by half the proportion There is no relationship between frequency and wavelength As the wavelength goes up, the frequency goes down by the same proportion As the wavelength goes up, the frequency also goes up by the same proportion As the wavelength goes up, the frequency also goes up by twice the proportion
As the wavelength goes up, the frequency goes down by the same proportion
When is Mercury visible in the night sky? Select one: It can be seen until about midnight At most, 2 hours before sunrise or 2 hours after sunset It can never be seen in the night sky It can be seen at any time of night
At most, 2 hours before sunrise or 2 hours after sunset
A hot, glowing, opaque solid, liquid or gas emits which type of spectrum? Select one: Absorption spectrum Continuous spectrum Emission spectrum
Continuous spectrum
Imagine that you are on the surface of Earth (below the atmosphere) and you're observing the Sun. Which of the following spectra would you observe by analyzing the sunlight? Select one: Bright line emission spectrum Continuous spectrum Dark line absorption spectrum
Dark line absorption spectrum
Imagine that you observe the Sun while in your space ship far above Earth's atmosphere. Which of the following spectra would you observe by analyzing the sunlight? Select one: Bright line emission spectrum Dark line absorption spectrum Continuous spectrum
Dark line absorption spectrum
Stars wouldn't appear to twinkle if Select one: stars were bigger in size. Earth rotated slower. stars were closer to Earth. Earth didn't have an atmosphere.
Earth didn't have an atmosphere.
What is the Copernican Principle? Select one: A. The stars are farther than the Sun B. The Sun is at the center of all things C. Earth is not in any position of cosmic significance D. Objects always move in circular motion
Earth is not in any position of cosmic significance
Meteor showers such as the Perseids in August are caused by Select one: nuclear reactions in the upper atmosphere triggered by an abnormally large meteoritic particle entering the upper atmosphere. the breakup of asteroids that hit our atmosphere at predictable times. passing asteroid triggering auroral displays. Earth passing through the debris left behind by a comet as it moves through the inner Solar System.
Earth passing through the debris left behind by a comet as it moves through the inner Solar System.
Our summer is somewhat longer than our winter (defined by the times between the solstices not by the weather) because Select one: Earth travels somewhat faster when it is closer to the Sun. we have a leap year once every four years. Earth spins counterclockwise about its own axis. there is an odd number of days in the year.
Earth travels somewhat faster when it is closer to the Sun.
Consider a planet as it moves in retrograde motion. Over the course of several nights, how will the planet appear to move relative to the background stars? Select one: A. East to west B. West to east C. It will move randomly, as planets move differently than the stars D. It will not move at all, as planets do not move with the stars
East to West
For a person on Earth, the planets always appear close to this line on the celestial sphere. Select one: Celestial equator Ecliptic Local celestial meridian Zenith
Ecliptic
How often do spring tides occur? Select one: Every new or full Moon Only at first and third quarter Moon Only on the first day of spring. On both the first day of spring and the first day of fall
Every new or full Moon
Since the Moon always presents the same side to the Earth, the "dark side of the Moon" is always dark. Select one: True False
False
The Copernican model did a better a job of predicting planetary behavior than did the Ptolemaic model. Select one: A. True B. False
False
The area swept out by Uranus in one Earth week is the same area swept out by Neptune in the same time. Select one: True False
False
The eccentricity, e, gives us the size of an ellipse. Select one: True False
False
The number of waves that pass a point each second measures which of the following? Select one: Wave period Wavelength Frequency Amplitude
Frequency
What color star will you never see? Select one: Green Stars can appear to be any color White Red Blue
Green
In what way did Newton improve Kepler's Laws? Select one: He found that the orbit was not always an ellipse He discovered the variation in orbital speed He discovered the dependence on mass in the Third Law He determined the astronomical unit
He discovered the dependence on mass in the Third Law
What is the composition of comets? Select one: Rocky core with a gaseous atmosphere All gaseous Icy mud All rocky
Icy Mud
What is the present leading theory for the Moon's formation? Select one: Fission of the early Earth due to its rapid rotation into two fragments Capture of a wandering object by the gravitational field of Earth Impact of a large object with the early Earth, followed by coalescence and capture of the resulting fragments Co-formation of the Earth and Moon out of the same protoplanetary material as nearby objects None of the theories listed here gives an acceptable model
Impact of a large object with the early Earth, followed by coalescence and capture of the resulting fragments
The principal culture that transferred Greek astronomical knowledge to Renaissance Europe was Select one: A. Chinese. B. Byzantine. C. Mongol. D. Mayan. E. Islamic.
Islamic
What made Kepler's First Law of planetary motion so revolutionary? Select one: It stated that planets move on ellipses, not perfect circles It was the first to assume that the Sun was the center of the Solar System Although planets move on ellipses, the orbital eccentricity is so small the orbits are basically circular For the first time in history, real data was used to find a description for how planets moved
It stated that planets move on ellipses, not perfect circles
What would happen to Earth if the Sun's gravity were suddenly "turned off"? Select one: It would move off in a straight line It would slowly spiral away from the Sun It would fall into the Sun Nothing. It would continue to orbit the Sun It would move off in a spiral-like motion
It would move off in a straight line
Earth passes through its perihelion position (its closest approach to the Sun) in Select one: March. September. July. January.
January
Galileo's observation of four moons orbiting ______ was so revolutionary Select one: A. Mars B. Saturn C. Neptune D. Jupiter E. Uranus
Jupiter
If we lived in a Solar System with only one planet, which of Kepler's laws could never be discovered observationally? Select one: Kepler's First Law Kepler's Second Law Kepler's Third Law All of them
Kepler's Third Law
How does orbital speed at aphelion (farthest from the Sun) compare to the speed at perihelion (closest to the Sun)? Select one: Lower Same Higher Depends on the object
Lower
Which terrestrial planet do you think has the best possibilities for hosting life either now or in the past? Select one: Mercury Venus Mars because: Select one: the other terrestrial planets are too cold. this planet has an extensive atmosphere that's needed for protecting possible lifeforms. this planet is most like Earth in size and mass. there's substantial evidence that water flowed on its surface in the past. it's the closest planet to Earth.
Mars; there's substantial evidence that water flowed on its surface in the past.
The planet ______ has the highest variation in orbital in orbital speed Select one: Uranus Mercury Earth Mars Jupiter
Mercury
Using careful observations from Earth, what other planet(s) besides Venus shows a full sequence of phases? Select one: A. Mercury B. Mars C. Jupiter D. Saturn E. All planets go through a sequence of phases
Mercury
Which planetary orbit has the highest eccentricity? Select one: Earth Mercury Jupiter Mars Uranus
Mercury
Which planets have a rocky, relatively dense composition? Select one: Jupiter, Saturn, Uranus, and Neptune Mercury, Venus, Earth, and Mars Uranus, Neptune, Earth, and Mars Jupiter, Saturn, Earth, and Mars
Mercury, Venus, Earth, and Mars
Which of the following names applies to a bright streak produced when a fragment of interplanetary debris plunges through the atmosphere? Select one: Comet Meteor Meteoroid Meteorite
Meteor
When did the majority of the cratering on the Moon occur? Select one: At about equal rates throughout its history In one short meteor storm Mostly early in its history Mostly very recently
Mostly early in its history
A planet moving in retrograde motion will, over the course of one night, appear to move Select one: A. move randomly, as planets move differently than the stars. B. not move at all, as planets do not move with the stars. C. move west to east. D. move east to west.
Move East to West
A dwarf planet satisfies which of the following: Select one: it orbits the Sun. it's massive enough that its own gravity has caused its shape to be approximately spherical. it has cleared the neighborhood around its orbit of other bodies. All of the above Only the first two conditions
Only the first two conditions
Which of the following is not a way in which the terrestrial and jovian planets differ? Select one: The orbits of the terrestrial worlds are relatively close together, while the orbits of the jovian worlds are far apart The jovian planets have orbits that are highly inclined to the ecliptic and do not revolve in the same direction as the terrestrial planets The terrestrial worlds are small and dense, while the jovian worlds are large and gaseous The terrestrial worlds have few or no moons, while the jovian worlds have many moons
The jovian planets have orbits that are highly inclined to the ecliptic and do not revolve in the same direction as the terrestrial planets
What have seismic studies discovered about the core of Earth? Select one: The outer core actually has a higher density than the inner core There's a lost civilization of people living at the center of the Earth The outer core forms a solid shell around the liquid inner core The outer core is liquid; the inner core is solid
The outer core is liquid; the inner core is solid
Ptolemy's model also predicted that the distances to the planets would change as they orbited Earth. When a planet was in retrograde motion, what did Ptolemy's model predict about the distance to the planet? Select one: A. The planet was at its minimum distance from Earth B. The planet was as its average distance from Earth (i.e., neither a maximum nor a minimum) C. The planet was at its maximum distance from Earth
The planet was at its minimum distance from Earth
How does the semimajor axis length change with increasing eccentricity? Select one: The semimajor axis decreases in length with as the eccentricity increases The semimajor axis does not change in length as the eccentricity increases The semimajor axis increases in length as the eccentricity increases
The semimajor axis does not change in length as the eccentricity increases
How does the speed of radio waves compare to the speed of visible light? Select one: Radio waves are much slower Radio waves are much faster They both travel at the same speed
They both travel at the same speed
That Mars takes longer to orbit the Sun than Earth does is a described by which of Kepler's laws? Select one: First Law Second Law Third Law
Third Law
In the past, most of the landmass on Earth was concentrated in a single, large continent. Select one: True False
True
Planets do twinkle for the same reason stars twinkle. Select one: True False
True
Galileo used his observations of the changing phases of Venus to demonstrate that Select one: A. the Sun moves around the Earth. B. the Moon orbits the Earth. C. Earth is a sphere. D. the Universe is infinite in size. E. Venus follows an orbit around the Sun rather than around the Earth.
Venus follows an orbit around the Sun rather than around the Earth.