The Solar System Chapters 6 & 7
Which of the following is not a major pattern of motion in the solar system?
Nearly all comets orbit the Sun in same direction and roughly the same plane.
Process of Science: Explain how technology advances help address astronomical questions.
New technologies allow us to study objects in the Universe in more detail (e.g., adaptive optics), over more wavelengths (e.g., space telescopes), and more efficiently than before (e.g., with larger cameras and faster computers). These advances allow us to test scientific theories by having a wider range of objects to compare and by learning about the physical processes in each object in more detail.
Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.)
Observatory X can detect dimmer stars and Observatory Y reveals more detail in images.
Suppose you view the solar system from high above Earth's North Pole. Which of the following statements about planetary orbits will be true?
All the planets orbit counterclockwise around the Sun.
What is a CCD?
It is an electronic detector that can be used in place of photographic film for making images.
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
It is closer to the stars.
In what way is Pluto more like a comet than a planet?
It is made mostly of rock and ice.
What is the Oort cloud?
It is not really a cloud at all, but rather refers to the trillion or so comets thought to orbit the Sun at great distances.
What do we mean by the diffraction limit of a telescope?
It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images.
Which of the following best describes the development of astronomical telescopes over the past 60 years?
The world's most powerful telescope remained the same for most of this period, but in the past 20 years many new and more powerful telescopes have been built.
Which of the following observations indicates that conditions on Mars may have been suitable for life in the past?
There are dried-up riverbeds on Mars.
Which of the following is not a characteristic of the inner planets?
They all have substantial atmospheres.
Which of the following is always true about images captured with X-ray telescopes?
They are always displayed in false color.
Which of the following studies is best suited to a time monitoring experiment?
studying whether a particular star's brightness is steady or variable
What do we mean by the diffraction limit of a telescope?
It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.
Which of the following statements about Pluto is not true?
It is the largest known object that is considered to be a dwarf planet.
What is the purpose of adaptive optics?
to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground
Which of the following is always true about images captured with X-ray telescopes?
They are always shown with colors that are not the true colors of the objects that were photographed.
The stars in our sky twinkle in brightness and color because of
turbulence in the Earth's atmosphere.
Which of the following is not a characteristic of the outer planets?
They have very few, if any, satellites.
Which of the following effects is caused by atmospheric turbulence?
twinkling of stars
What is the Kuiper belt?
a region of the solar system beginning just beyond the orbit of Neptune that contains many icy comets
What is the angular resolution of the human eye?
about 1 arcminute, or 1/60 of a degree
Venus has a higher average surface temperature than Mercury. Why?
because its surface is heated by an extreme greenhouse effect
What causes stars to twinkle?
bending of light rays by turbulent layers in the atmosphere
Where are most of the known asteroids found?
between the orbits of Mars and Jupiter
Which of the following wavelength regions cannot be studied with telescopes on the ground?
both B and C
When we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals except
carbon dioxide.
Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is
much larger.
Based on the frequency with which we see comets from Earth, astronomers estimate the total number of comets in the solar system to be
1 trillion.
Currently, the largest optical telescope mirrors have a diameter of
10 m.
Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?
A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light.
Explain how adaptive optics works.
Adaptive optics corrects for atmospheric distortion by following the distortion of a bright star, possibly an artificial star created by a laser, and rapidly changing the shape of a mirror using computer-controlled actuators to compensate for the distortion.
Which jovian planet does not have rings?
All the jovian planets have rings.
Suppose an astronomer proposed to build a major observatory on the campus of your school. Would it make a good observing site? Explain why or why not.
Answers will vary somewhat with location, but in general campuses are bright environments that are poor observing sites from a light pollution standpoint. Other factors students may mention might include light from surrounding or nearby cities, excessive cloudiness or rain, windy area with a lot of turbulence, and low altitude with lots of atmosphere above.
How do asteroids differ from comets?
Asteroids are rocky bodies and are denser than the comets, which are made of icy material.
Which of the following is not a real difference between asteroids and comets?
Asteroids orbit the Sun while comets just float randomly around in the Oort cloud.
In what way is Venus most similar to Earth?
Both planets are nearly the same size.
Why was it advantageous for the Voyager mission to consist of flybys rather than orbiters?
Each individual spacecraft was able to visit more than one planet.
Which of the following is a principal advantage of CCDs over photographic film?
CCDs capture a much higher percentage of the incoming photons than does film.
Which of the following best describes the principle advantage of CCDs over photographic film?
CCDs capture a much higher percentage of the incoming photons than film.
Which is the densest planet in the solar system?
Earth
The largest effective telescope, created by radio interferometry, is the size of
Earth.
A larger telescope will always have a higher spectral resolution than a smaller telescope when observing at the same wavelength.
F
A radio telescope and an optical telescope of the same size have the same angular resolution.
F
All comets orbit the Sun in the same direction as the planets.
F
All the planets in the solar system have at least one moon.
F
Improvements in technology will eventually allow the entire electromagnetic spectrum to be observed from high mountaintop observatories.
F
Professional astronomical telescopes generally have a much greater magnification than the telescopes you can buy in stores.
F
The Hubble Space Telescope is famous because, at least at the time of its launch, it was the largest visible light telescope ever built.
F
The planet Uranus held a special place in the mythology of the ancient Romans.
F
X-ray telescope mirrors are very similar to optical telescope mirrors.
F
Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light?
Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.
Explain what an interferometer is and give an example.
Interferometers are groups of telescopes that have been linked together and interfere the light waves that they receive to achieve the same angular resolution (but not the collecting area) as a much larger telescope. An example is the Very Large Array in New Mexico, which links 27 telescopes, each the size of a large house, over tens of miles.
What is the purpose of interferometry?
It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.
What does the technique of interferometry allow?
It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.
How is Einstein's famous equation, E= mc2, important in understanding the Sun?
It explains the fact that the Sun generates energy to shine by losing some 4 million tons of mass each day.
Which of the following is not true of Mercury?
It has been studied closely by several NASA spacecraft.
What is meant by spectral resolution?
It is a measure of how close two spectral lines can be distinguished.
How does the Sun's mass compare with that of the planets?
It is a thousand times more massive than all the planets combined.
Which of the following best describes what we mean by the focal plane of a telescope?
It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope.
Which of the following statements about the recently-discovered object Eris is not true?
It is thought to be the first example of a new class of object.
What is the purpose of adaptive optics?
It reduces blurring caused by atmospheric turbulence for telescopes on the ground.
Why has NASA sent recent orbiters to Mars on trajectories that required them to skim through Mars's atmosphere "aerobraking" before settling into their final orbits?
It saved money because the spacecraft used atmospheric drag to slow down rather than needing to carry enough fuel to slow by firing rocket engines.
The diffraction-limited resolution of a 10-meter telescope is about 0.01 arcsecond for visible light. Would you expect the angular resolution of a 20-meter space telescope observing visible light to be better than, equal to, or worse than 0.01 arcsecond? Explain.
It would be better than 0.01 arcsecond because a larger telescope means a better diffraction-limited resolution for the same wavelength of light, and the location in space eliminates problems of atmospheric distortion.
The diffraction-limited resolution of a 10-meter telescope is about 0.01 arcsecond for visible light. Would you expect the actual angular resolution of a Keck 10-meter telescope in Hawaii to be better than, equal to, or worse than 0.01 arcsecond? Explain.
It would be worse than 0.01 arcsecond because of the distortion caused by atmospheric turbulence.
The diffraction-limited resolution of a 10-meter telescope is about 0.01 arcsecond for visible light. Would you expect the angular resolution of a 10-meter radio telescope to be better than, equal to, or worse than 0.01 arcsecond? Explain.
It would be worse than 0.01 arcsecond because radio waves have much longer wavelength than visible light, and hence poorer angular resolution for the same size telescope.
Imagine that an alien spaceship crashed onto Earth. Which statement would most likely be true?
It would crash in the ocean.
Pluto is different from the outer planets in all of the following ways except which one?
Its surface temperature is very cold.
The jovian planets in our solar system are
Jupiter, Saturn, Uranus, and Neptune.
What do astronomers mean by light pollution?
Light pollution is light from human sources that makes it difficult to see the stars at night
What do astronomers mean by light pollution?
Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.
Which planet (besides Earth) has been visited by the largest number of robotic spacecraft?
Mars
Which planet, other than Earth, has visible water ice on it?
Mars
The terrestrial planets in our solar system are
Mercury, Venus, Earth, and Mars.
The most metal-rich terrestrial planet is
Mercury.
Which of the following statements is not an observed pattern of motion in our solar system?
Most planets orbit at the same speed.
Why do astronomers need different telescope designs to observe across the electromagnetic spectrum?
Photons of different energy behave differently and require different collection strategies.
Which of the following is not a pattern of motion in our solar system?
Planets all rotate in the same direction.
Which of the following is not an advantage of spacecraft flybys over ground-based telescope observations?
Spacecraft can monitor changes in a planet's atmosphere over long times.
What is spectral resolution? Why can a large telescope allow for a higher spectral resolution than a smaller telescope?
Spectral resolution is a measure of the amount of detail that can be seen in a spectrum (i.e., how well it can separate out two spectral features from each other). It depends on how widely the light from a telescope is spread out, but the trade-off is that the more the light is spread out, the dimmer it becomes until it becomes undetectable. Since a large telescope gathers more light than a smaller telescope, it can spread the light out further and achieve a higher resolution.
All four of the giant outer planets-Jupiter, Saturn, Uranus, and Neptune-have rings.
T
All planets orbit the Sun in the same direction (counterclockwise as viewed from above Earth's North Pole).
T
Most astronomical objects emit light over a broad range of wavelengths.
T
Oceans cover more of Earth's surface than land.
T
Process of Science: If any single test of a scientific hypothesis contradicts it, the hypothesis must be revised.
T
The angular resolution of a telescope is never less than its diffraction limit.
T
The jovian planets have no solid surface.
T
The lens in your eye forms an upside-down image of the world.
T
The more massive planets in the solar system tend to be less dense than the lower mass planets
T
X rays from astronomical objects can only be detected from telescopes in space.
T
Which of the following statements best describes the two principal advantages of telescopes over eyes?
Telescopes can collect far more light with far better angular resolution.
Which of the following statements best describes the two principle advantages of telescopes over eyes?
Telescopes can collect far more light with far better angular resolution.
Which of the following is not a major reason why astronomers would like an observatory on the far side of the Moon?
Telescopes on the Moon could see objects in all parts of the sky equally well, whereas telescopes on Earth can see only portions of the sky that depend on their latitude
Which of the following is not a major difference between the terrestrial and jovian planets in our solar system?
Terrestrial planets contain large quantities of ice and jovian planets do not.
How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?
The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.
Which of the following telescopes would benefit most from adaptive optics?
The Keck I Telescope on Mauna Kea.
Consider the following statement: "Rocky asteroids are found primarily in the asteroid belt and Kuiper belt while icy comets are found primarily in the Oort cloud" What's wrong with this statement?
The Kuiper belt contains icy comets, not rocky asteroids.
Which of the following statements about our Sun is not true?
The Sun's diameter is about 5 times that of Earth.
Which of the following statements about the asteroid belt is not true?
The combined mass of all the asteroids is roughly the same as the mass of Earth.
The following statements are all true. Which one counts as an "exception to the rule" in being unusual for our solar system?
The diameter of Earth's Moon is about 1/4 that of Earth.
Which of the following statements about light focusing is not true?
The focal plane of a reflecting telescope is always located within a few inches of the primary mirror.
What is the primary reason why a Pluto flyby mission would be cheaper than a Pluto orbiter?
The fuel needed for an orbiter to slow down when it reaches Pluto adds a lot of weight to the spacecraft.
Suppose you have two small photographs of the Moon. Although both look the same at small size, when you blow them up to poster size one of them still looks sharp while the other one becomes fuzzy (grainy) looking. Which of the following statements is true?
The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy.
The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see?
The photo will seem to show only one star rather than two.
Suppose you point your telescope at a distant object. Which of the following is not an advantage of taking a photograph of the object through the telescope as compared to just looking at the object through the telescope?
The photograph will have far better angular resolution than you can see with your eye.
Suppose the two headlights on a car are separated by 1 meter and you are looking at the car from a distance of 2 kilometers. What is the angular separation of the headlights? Can your eyes resolve the two headlights? (HINT: Recall the angular separation formula α = s/2(pi)d × 360°; the angular resolution of the human eye is about 0.020°.)
The separation of the headlights is s = 1 m, and their distance is d = 2 km. Thus, their angular separation is: a = 1m / 2(pi) x 2,000m x 360 degrees = 0.028 degrees. This is a slightly wider separation than the angular resolution of your eyes, so you can resolve the two headlights.
Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates?
The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.
Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes?
The two stars will look like a single point of light.
Which planet listed below has the most extreme seasons?
Uranus
Which planet has the highest average surface temperature, and why?
Venus, because of its dense carbon dioxide atmosphere
The planet closest in size to Earth is
Venus.
The planet in our solar system with the highest average surface temperature is
Venus.
Given that the Moon has an angular diameter of about 0.5° and an average distance of about 380,000 km from Earth, calculate its actual diameter. (HINT: Recall the angular separation formula α = s/2(pi)d × 360°.)
We are given α = 0.5° and d = 380,000. Thus, we must first solve the angular separation equation for s: α = s/2(pi)d × 360° ⇒ s = 2(pi)d/360 degrees × α Now we substitute the numbers. s = 2(pi) x 380,000 km / 360 degrees x 0.5 degrees = 3,316 km The Moon's diameter is about 3,300 km.
Which of the following statements about Mars is not true?
We could survive on Mars without spacesuits, as long as we brought oxygen in scuba tanks.
Where does nuclear fusion occur in the Sun?
in its core
The Chandra X-Ray Observatory must operate in space because
X rays do not penetrate Earth's atmosphere.
Which of the following is farthest from the Sun?
a comet in the Oort cloud
What is an artificial star?
a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations
Which planet has a ring system?
all of the above
The Cassini mission to Saturn consists of
an orbiter that orbits Saturn and a probe that descended to the surface of Titan.
Telescopes operating at this wavelength must be cooled to observe faint astronomical objects.
extreme infrared
Order the following in order of increasing efficiency of detecting photons of visible light
eye, photographic film, CCD
Which of the following is not one of the three main categories of observation generally used by astronomers?
filtering to look at just a single color from an object
Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have?
high spectral resolution
What are the main constituents of the jovian planets?
hydrogen and helium
At which wavelength range is there no current or planned space observatory?
radio
In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?
radio
In what wavelength range was interferometry first routinely used?
radio
Which of the following wavelength regions can be studied with telescopes on the ground?
radio, visible, and very limited portions of the infrared and ultraviolet regions
Which of the following best describes Pluto in terms of the general characteristics of terrestrial and jovian planets?
size and solid surface similar to terrestrial planets; distance similar to jovian planets
Mars has two moons that are most similar in character to
small asteroids.
Which of the following studies is best suited to astronomical observations that fall into the category called timing?
studying how a star's brightness varies over a period of 3 years
Astronomers have decided that, rather than being a planet, Pluto is really just a large member of
the Kuiper belt.
What does angular resolution measure?
the angular size of the smallest features that the telescope can see
Which moons are sometimes called the Galilean moons?
the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto
Which of the following could not be measured by an observation that uses only imaging?
the rate at which a variable star brightens and dims
Which of the following is not an exception to the general patterns in the solar system?
the rings of Saturn
Which of the following could not be determined by an observation that uses only spectroscopy?
the size of a distant galaxy
What is aerobraking?
the technique of using a planetary atmosphere to change the orbit of a spacecraft
Which of the following is not a good reason to place observatories on remote mountain tops?
to be able to observe at radio wavelengths