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Astronomy test 2
Terms in this set (80)
When the atom's electrons step down to lower energy levels in a thin cloud of hot gas, what is produced?
an emission line spectrum
If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?
The planet is rotating.
Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)
The blue star has a hotter surface temperature than the red star.
Why do astronomers need different telescopes at different locations to observe across the electromagnetic spectrum?
Photons of different wavelengths behave differently and so require different collection strategies.
Which of the following wavelength regions cannot be studied at all with telescopes on the ground?
Earth's atmosphere is the most transparent to which type of light?
From lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation?
radio, infrared, visible light, ultraviolet, X-rays, gamma rays
When observing visible light through a prism or diffraction grating, how can you tell if a line spectrum is an emission spectrum or an absorption spectrum?
An emission spectrum has bright lines on a dark background and an absorption spectrum has dark lines on a rainbow background.
Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?
the wavelengths of spectral lines in the star's spectrum
The stars in our sky twinkle in brightness and color because of ________.
turbulence in Earth's atmosphere
What is the purpose of adaptive optics?
to reduce blurring caused by atmospheric turbulence for telescopes on the ground
If we say that a material is opaque to ultraviolet light, we mean that it ________.
absorbs ultraviolet light
We are measuring the spectra of two hydrogen gas clouds. The laboratory frame wavelength of one hydrogen line is 656.2 nm. Cloud A's emission line wavelength is 660.1 nm and Cloud B's emission line wavelength is 670.1 nm. What can we conclude about these clouds?
They are both receding from us, and Cloud B is receding faster than Cloud A.
The angular separation of two stars is 0.1 arcseconds and you photograph them with the Discovery Channel Telescope using its 0.24 arc second resolution mode, what would you see?
The photo will seem to show only one star rather than two.
How does the light-collecting area of an 8-meter telescope compare to that of a 1-meter telescope?
The 8-meter telescope has 64 times the light-collecting area of the 1-meter telescope.
One star is emitting primarily visible light and another star is emitting primarily infrared light. Which star is hotter?
the star emitting visible light
The Chandra X-ray Observatory must operate in space because
X-rays do not penetrate Earth's atmosphere.
Which of the following statements about X-rays and radio waves is not true?
X-rays travel through space faster than radio waves.
Which of the following statements is true of green grass?
It absorbs red light and reflects green light.
Which forms of light are lower in energy and frequency than the light that our eyes can see?
infrared and radio
Why did the solar nebula heat up as it collapsed?
As the cloud shrank, its gravitational potential energy was converted to thermal energy.
Why did the solar nebula flatten into a disk?
It flattened as a natural consequence of collisions between particles in the nebula, changing random motions into more orderly ones.
According to our theory of solar system formation, why do all the planets orbit the Sun in the same direction and in nearly the same plane?
The laws of conservation of energy and conservation of angular momentum ensure that any rotating, collapsing cloud will end up as a spinning disk.
Why do Earth rocks have much younger ages than most meteorites?
Most Earth rocks have been melted and reformed since Earth formed from the solar nebula.
In essence, the solar nebular theory states that ________.
ur solar system formed from the collapse of an interstellar cloud of gas and dust
Based on studies of the composition of stars and interstellar gas clouds, what was the approximate chemical composition of the solar nebula?
98% hydrogen and helium, 2% everything else
According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size?
It got hotter, its rate of rotation increased, and it flattened into a disk.
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 do we mean by the frost line when we discuss the formation of planets in the solar nebula?
It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.
What do we mean by the period of heavy bombardment in the context of the history of our solar system?
the first few hundred million years after the planets formed, which is when most impact craters were formed
According to modern scientific dating techniques, approximately how old is the solar system?
4.5 billion years
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.
What is the primary reason we divide the ingredients of the solar nebula into four categories (hydrogen/helium gas; hydrogen compound; rock; metal)?
The temperature at which these materials condense into a solid varies considerably.
According to our present theory of solar system formation, which of the following statements about the growth of terrestrial and jovian planets is not true?
The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.
Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support our theory about how the terrestrial planets formed?
The meteorites' appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.
According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons?
As the growing jovian planets captured gas from the solar nebula, the gas formed swirling disks around them, and moons formed from condensation accretion within these disks.
Which of the following is not evidence supporting the idea that our Moon formed as a result of a giant impact?
The Pacific Ocean appears to be a large crater—probably the one made by the giant impact.
Why are terrestrial planets more dense than the jovian planets?
Only dense materials could condense in the inner solar nebula.
Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?
Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.
Which of the following observations of an extrasolar planet system would be inconsistent with the nebular theory of planet formation?
a system in which all the planets orbit in completely diﬀerent planes
Under what circumstances can differentiation occur in a planet?
The planet must have a molten interior.
Which of the following best describes impact cratering?
the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
How have we been able to construct detailed maps of surface features on Venus?
by using radar from spacecraft that were sent to orbit Venus
Why would the weather become more severe as the greenhouse effect increased?
Warming would increase the evaporation of the oceans, leading to more water in the atmosphere and more frequent and severe storms.
Given the rate at which human activity is increasing CO2 levels, why can we not depend on the natural CO2 cycle to prevent global warming?
It operates too slowly.
What process initially caused the terrestrial planets to be hot enough to be entirely molten?
Why does the Moon have a layer of "powdery soil" on its surface?
It is the result of countless tiny impacts by small particles striking the Moon.
What observational evidence supports the idea that Mercury shrank after it formed?
the presence of many long, tall cliffs
Which of the following does not provide evidence that Mars once had abundant liquid water on its surface?
the presence of canali, discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell
The cores of the terrestrial worlds are made mostly of metal because ______
metals sunk to the centers a long time ago when the interiors were molten throughout
Which of the following best describes how the greenhouse effect works?
A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.
Why does the burning of fossil fuels increase the greenhouse effect on Earth?
Burning releases carbon dioxide into the atmosphere.
Most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude?
The maria formed after the heavy bombardment ended.
All of the statements below are true. Which one gives the primary reason why the surface of Venus today is some 450°C hotter than the surface of Earth?
Venus has a much stronger greenhouse effect than Earth.
Which internal heat source still actively generates heat within the terrestrial worlds today?
heat from radioactive decay
Why does Venus have such a large difference in temperature between its "no atmosphere" temperature and its actual temperature?
It has a large amount of carbon dioxide in its atmosphere.
The atmospheres of Venus and Mars are primarily composed of carbon dioxide. Why is the surface of Venus so much hotter than the surface of Mars?
Venus' atmosphere is thousands of times thicker than Mars' atmosphere.
Which two factors are critical to the existence of the carbon dioxide (CO2) cycle on Earth?
plate tectonics and liquid water oceans
Which of the following is not an expected consequence of global warming?
he entire Earth will warm up by the same amount
What is the main reason that Mars, compared to Earth, has become so geologically inactive?
What is the primary reason an icy moon is likely to be more geologically active than a rocky moon of the same size?
Ice has a lower melting point than rock.
Which of the following best describes the composition of the particles forming Saturn's rings?
Where is Jupiter's strong magnetic field generated?
metallic hydrogen layer
What is the most likely method in which Jupiter generates its internal heat?
by contracting, changing gravitational potential energy into thermal energy
The large Jovian satellites have sizes comparable to Mercury. Why do they have an icy composition compared to Mercury's rocky composition?
They formed beyond the frost line, where ices were more abundant than metals and rock.
Why is Jupiter denser than Saturn?
The extra mass of Jupiter compresses its interior to a greater extent than that of Saturn.
How do the jovian planet interiors differ from one another?
All have cores of about the same mass, but differ in the amount of surrounding hydrogen and helium.
Which of the following is not a general characteristic of the four jovian planets in our solar system?
They are higher in average density than are the terrestrial planets.
The Huygens probe took numerous pictures as it descended to Titan's surface in 2005. What did the pictures show?
features of erosion, including what appeared to be dry river valleys and lakebeds
Which statement about planetary rings is not true
Saturn's rings formed along with its moons 4.6 billion years ago.
Overall, Jupiter's composition is most like that of ________.
What atmospheric constituent is responsible for the blue color of Uranus and Neptune?
Which of the following gases is not a significant ingredient of the jovian planet atmospheres?
Which of the following best explains why many jovian moons have been more geologically active than the Moon or Mercury?
Jovian moons are made mostly of ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.
Which of the following is not a piece of evidence supporting the idea that Europa may have a subsurface ocean?
Astronomers have detected small lakes of liquid water on Europa's surface.
Which statement about Saturn's rings is not true?
The rings must look much the same today as they did shortly after Saturn formed.
According to current understanding, which of the following is required for a planet to have rings that last for a very long time?
The planet must have many small moons that orbit relatively close to the planet in its equatorial plane.
According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn?
Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula.
Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which of the following explains why?
Temperatures on Jupiter and Saturn are too high for methane to condense.
Which jovian planet should have the most extreme seasonal changes?
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