AST 100 exam 2
Most people are familiar with the rise and fall of ocean tides. Do tides also affect land?
Yes, though land rises and falls by a much smaller amount than the oceans.
Suppose you are in an elevator car when the elevator cable breaks. Which of the following correctly describes what happens and why.
You float weightlessly within the elevator car because you and the elevator both begin to accelerate downward at the same rate.
________ can be created by a hot, dense object and can make a rainbow
a continuous spectrum
Our Moon has
a diameter more than 1/4 the diameter of Earth.
The solar corona is
a hot gas located above the Sun's visible surface
For a star (or other astronomical object), a Doppler shift is a shift in the wavelength of spectral lines in an object's spectrum. The amount of this shift is a measure of the object's
speed toward or away from Earth
Where would you expect terrestrial planets to form in the solar nebula?
anywhere between 0.3 AU and the frost line
Jovian planets
are larger in size, more massive and lower in average density, have more moons, orbit farther from the Sun, & are larger in mass
As the cloud shrinks in size, its rate of rotation __________ because __________.
speeds up / its total angular momentum is conserved
If the Sun were to shrink, its angular momentum would__________ and its gravitational potential energy would __________
stay the same / decrease
As an object shrinks in size, its mass
stays the same
As the cloud collapses, the overall force of gravity draws the cloud inward __________ because __________.
gradually becomes stronger / the strength of gravity follows an inverse square law with distance
The gravitational potential energy of a contracting interstellar cloud
gradually transforms into other forms of energy.
An asteroid that is moving farther from the Sun is gaining
gravitational potential energy
The orbital energy of an asteroid orbiting the Sun is the sum of its
gravitational potential energy and kinetic energy
The Chandra X-ray observatory focuses X rays with ____________ mirrors.
grazing incidence
An electron can be ejected from an atom if it absorbs a photon that
has more energy than is needed to raise the electron to the highest energy level
What is Jupiter's main ingredient?
hydrogen and helium
The composition of the solar nebula was 98%
hydrogen and helium.
What do hydrogen compounds condense into?
ice
As the cloud shrinks in size, its central temperature __________ as a result of its __________
increases / gravitational potential energy being converted to thermal energy
Spectrographs
separate the various colors of light, allowing astronomers to determine stellar composition and many other stellar properties.
An object's angular momentum depends on its mass, its
size (radius) and rotation rate
Newton's Second Law
The equation one... When a force, F, acts on a body of mass, m, it produces in it an acceleration, a, equal to the force divided by the mass. a = m/f Or: f = m × a
The solar system contains vast numbers of small bodies, which we call asteroids when they are rocky and comets when they are icy. These small bodies are concentrated in the region(s) of the solar system that we call
the Kuiper belt, the asteroid belt, the Oort cloud
Consider Earth and the Moon. As you should now realize, the gravitational force that Earth exerts on the Moon is equal and opposite to that which the Moon exerts on Earth. Therefore, according to Newton's second law of motion
the Moon has a larger acceleration than Earth, because it has a smaller mass
Notice that the Sun's spectrum appears brightest (or most intense) in the yellow-green region. This fact tells us
the approximate temperature of the Sun's surface
When you are standing on a scale in an elevator, what exactly does the scale measure?
the force you exert on the scale
According to Newton's second law,
the greater the force exerted on an object, the greater the object's acceleration
The mathematical relationship between frequency and energy for any light wave is energy = Planck's constant × frequency, Therefore,
the higher the frequency, the higher the energy
The two laws of thermal radiation state that
the hotter objects emit more light (per unit area) at all wavelengths. The peak wavelength of the emitted light is shorter (higher energy) for hotter objects.
The mathematical relationship between wavelength and frequency for any light wave is wavelength × frequency = speed of light, Therefore,
the longer the wavelength, the lower the frequency
A star whose spectrum peaks in the infrared is:
cooler than our sun
Asteroids are made of
essentially the same materials as the terrestrial planets.
How much greater is the light-collecting area of a 6-meter telescope than a 3-meter telescope?
four times
Where could ice accrete (combine together) in the early solar system?
outer solar system
Now consider why the observed patterns of motion lead to the conclusion that the planets were not born in separate, random events. The reason for this conclusion is that, if the planets had been born in separate, random events, we would expect that
planetary orbits would have many different orientations and directions, rather than all being in the same direction and in the same plane
The light from Polaris travels through space in the form of
radiative energy
As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be
reater than your normal weight at rest
When on object's spectral lines are shifted from their rest wavelengths to longer wavelengths, we say that the object's spectrum shows a
redshift
A spectral line that appears at a wavelength of 321 nm in the laboratory appears at a wavelength of 328 nm in the spectrum of a distant object. We say that the object's spectrum is:
redshifted
The large research observatories on Mauna Kea use giant
reflecting telescopes
If you were standing on Venus, you would see the Sun
rise in the west and set in the east
The rock/metal condensation line marks the innermost boundary where
rock or metal could condense into solid flakes
For terrestrial planets to form,
rocks and metals must be present as solid flakes
The jovian planets are thought to have formed as gravity drew hydrogen and helium gas around planetesimals made of
rocks, metals, and ices
What substances were found within the inner 0.3 AU of the solar system before planets began to form?
rocks, metals, hydrogen compounds, hydrogen, and helium, all in gaseous form
Newton's second law of motion states that force equals mass times acceleration, or F=ma. Suppose you have already calculated the gravitational force, which we will call Fg , attracting Earth and the Moon. Then the amount of acceleration of Earth due to this force is
Fg divided by the mass of the Earth
How can you tell whether a star has a blueshift or a redshift?
Focus on the pair of lines near the right (red): If the star has this pair farther to the right than the Lab spectrum, then it is a redshift; if the star has this pair to the left of the Lab spectrum, it is a blueshift.
The terrestrial planets are
Mercury, Venus, Earth, and Mars
What is the order of our planets closest to farthest from the sun?
Mercury, venus, earth, mars, jupiter, saturn, uranus, neptune
Earth has two tidal bulges at all times. Approximately where are these bulges located?
One faces the Moon and one faces opposite the Moon.
Which of the following procedures would allow you to make a spectrum of the Sun similar to the one shown, though with less detail?
Pass a narrow beam of sunlight through a prism.
Some planets are made mostly of rock and metal, while other planets also contain large amounts of hydrogen. In general, which type of planet has a higher average density, and why?
Planets made of rock and metal have a higher density, because under similar temperature and pressure conditions, any volume of rock or metal will have a greater mass than the same volume of hydrogen.
Einstein's theory, like Newton's, predicts that, in the absence of air resistance, all objects should fall at the same rate regardless of their masses. Consider the following hypothetical experimental results. Which one would indicate a failure of Einstein's theory?
Scientists dropping balls on the Moon find that balls of different mass fall at slightly different rates.
Consider a spectral line with a rest wavelength of 750 nm. In the spectrum of Star A, the line is shifted to 751 nm. In the spectrum of Star B, the line is shifted to 749 nm. Which statement is true?
Star A is moving away from us and Star B is moving toward us.
Which of the following best describes why the Sun's spectrum contains black lines over an underlying rainbow?
The Sun's hot interior produces a continuous rainbow of color, but cooler gas at the surface absorbs light at particular wavelengths.
For which of the following other motions would your weight also be greater than your normal weight?
The elevator moves downward while slowing in speed.
The Sun's spectrum is an example of a(n)
absorption line spectrum
Cool, not-dense things take lines out of the rainbow is
an Absorption Spectrum
A spectral line is produced when
an electron in an atom, ion, or molecule gains or loses a precise amount of energy
Suppose we measure an emission line from an object in space to be 550nm. We know from the lab that it should be 500nm. How fast is the object moving away from us?
0.1 x the speed of light
Which of the following correctly describe patterns of motion in the solar system?
-Planets closer to the Sun move around their orbits at higher speed than planets farther from the Sun. -All the planets orbit the Sun in nearly the same plane -All the planets have nearly circular orbits.
Pluto's average distance from the Sun is
39.5 AU
Kirchoff's third Law of light
A cool, thin gas absorbs certain wavelengths from a continuous spectrum, leaving dark absorption lines in their place, superimposed on a continuous spectrum. Once again, these lines are characteristic of the composition of the intervening gas - they occur at precisely the same wavelengths as the emission lines produced by that gas at higher temperatures.
Kirchoff's second Law of light
A low-density, hot gas emits light whose spectrum consists of a series of bright emission lines that are charteristic of the chemical composition of the gas.
Kirchoff's first Law of light
A luminous solid or liquid, or a sufficiently dense gas, emits light of all wavelengths and so produces a continuous spectrum of radiation.
Which statement about a blueshift and a redshift is true?
A spectrum shows a blueshift when the object is moving toward us and a redshift when it is moving away from us.
Suppose that the Sun were to collapse from its current radius of about 700,000 km to a radius of only about 6000 km (about the radius of Earth). What would you expect to happen as a result?
A tremendous amount of gravitational potential energy would be converted into other forms of energy, and the Sun would spin much more rapidly.
Newton's First Law
An object in motion... Every body continues in a state of rest of a state of uniform motion in a straight line, unless it is compelled to change that state by a force acting on it.
The dwarf planet Eris was discovered in 2005, orbiting the Sun at an average distance about twice that of Pluto. In which of the following ways do Pluto and Eris differ from the terrestrial and jovian planets in our solar system?
Both Pluto and Eris are smaller than any of the terrestrial planets Both Pluto and Eris travel in more elliptical orbits than any of the terrestrial or jovian planets. Both Pluto and Eris are less massive than any of the terrestrial or jovian planets.
Why is Doppler famous?
Christian Doppler discovered that the frequency of waves coming from an object depends on the object's motion
Suppose we want to know what the Sun is made of. What should we do?
Compare the wavelengths of lines in the Sun's spectrum to the wavelengths of lines produced by chemical elements in the laboratory.
Newton's Third Law
Equal and Opposite...To every action, there is an equal and opposite reaction.
Two asteroids are orbiting the Sun on nearly identical orbits, & they happen to pass close enough to each other to have their orbits altered by this gravitational encounter. If one of the asteroids ends up moving to an orbit that is closer to the Sun, what happens to the other asteroid?
It will end up on an orbit that is farther from the Sun.
What's unusual about our Moon?
It's surprisingly large relative to the planet it orbits.
The jovian planets are
Jupiter, Saturn, Uranus, and Neptune
Newton's Universal Law of Gravitation
Kind of important to Astronomy... Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between their centers.
Comets
Leftover ice-rich planetesimals
A 10-meter telescope has a larger__________ area than a 4-meter telescope.
Light-collecting area
Scientifically, which of the following possible conclusions is justified from the patterns of motion alone
The planets were not each born in a separate, random event.
One tidal bulge faces toward the Moon because that is where the gravitational attraction between Earth and the Moon is strongest. Which of the following best explains why there is also a second tidal bulge?
The second tidal bulge arises because gravity weakens with distance, essentially stretching Earth along the Earth-Moon line.
Which planet is approximately halfway between Pluto's orbit and the Sun?
Uranus, the seventh planet from the Sun
On average, ________ has the hottest surface temperature of any planet in the solar system.
Venus
Are there any exceptions to the rule that planets rotate with small axis tilts and in the same direction as they orbit the Sun?
Venus and Uranus are exceptions.
The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is:
above Earths Atmosphere
Why does the Moon play a greater role in causing tides than the Sun?
because the gravitational attraction between Earth and the Moon varies more across Earth than does the gravitational attraction between Earth and the Sun
We say that the force of gravity follows an inverse square law with distance. This means that the force attracting two objects _________ as two objects come closer together.
become stronger
The Angular resolution of the Hubble Space Telescope is
better for shorter (bluer) wavelengths of light than for longer (redder) wavelengths of light.
When the lines are shifted to shorter wavelengths, we say that the object's spectrum shows a
blueshift
Where could rock accrete (combine together) in the early solar system?
both inner and outer solar system
The set of spectral lines that we see in a star's spectrum depends on the star's:
chemical composition
An apple contains_________________ that your body can convert into other forms energy.
chemical potential energy
The two objects we are concerned with are Earth and the spaceship, which both have constant masses. Therefore, the strength of gravity between them
decreases with the square of their distance apart
Which of the following factors determine how long it takes a planet to orbit the Sun?
distance from the Sun only
Which of the following factors determine a planet's average surface temperature?
distance from the Sun, reflectivity, and strength of greenhouse effect
The twin 10-m Keck telescopes can work together to obtain better angular resolution through a technique known as
interferometry
After the atoms in a gas cloud absorb photons of specific wavelengths (the wavelengths of the absorption lines) from a light bulb or star, the energy from these photons
is returned to space when the atoms re-emit photons with the same total amount of energy, but in random directions
An absorption line spectrum
is seen when a source of a continuous spectrum is viewed behind a cool gas under pressure.
Compared to an atom as a whole, an atomic nucleus:
is very tiny but has most of the mass.
Refracting telescopes
is what Galileo designed using lenses
Some nitrogen atoms have seven neutrons and some have eight neutrons. These two forms of nitrogen are
isotopes of each other
Rapidly moving comets have more_________ than slowly moving ones.
kinetic energy
You are in an elevator that is moving upward. As the elevator nears the floor at which you will get off, its speed slows down. During this time when the elevator is moving upward with decreasing speed, your weight will be
less than your normal weight at rest
Today, scientists have a theory (the nebular theory) that explains all the major characteristics of the solar system. In science, we expect a theory like this not only to explain the observed characteristics of our solar system but also to
make testable predictions about other solar systems
Compared to their values on Earth, on another planet your
mass would be the same but your weight would be different.
Nuclear fusion in stars converts some of the__________ of hydrogen nuclei into light and heat.
mass-energy
Hydrogen compounds are
molecules that contain hydrogen and one or more other elements, such as water (H2O), methane (CH4), and ammonia (NH3)
The composition of the Sun is
mostly hydrogen and helium
Beyond the frost line, planetesimals were made
mostly of ice, but mixed with rock and metal
The electron that loses the most energy is the one that
moves the greatest distance between the energy levels (blue circles) in its downward transition
To calculate the gravitational force between two objects we __________, and then multiply by the gravitational constant G
multiply the two masses, divide by their distance squared
The neon "OPEN" sign appears reddish-orange because
neon atoms emit many more yellow and red photons than blue and violet photons
If Earth were twice as far from the Sun, the force of gravity attracting Earth to the Sun would be
one-quarter as strong
The interior of the Sun effectively produces a continuous spectrum. These photons escape to space
only after passing through a thin, cooler layer of gas atthe Sun's surface
Venus rotates in a direction
opposite to the rotation of the other terrestrial planets.
Compared to its angular momentum when it is farthest from the Sun, Earth's angular momentum when it is nearest to the Sun is
the same
According to Newton's third law
the strength of the force that the object on the left exerts on the object on the right has to be exactly the same (but in an opposite direction) as the force the object on the right exerts on the object on the left
Due to its much higher density, water heated to 80 degrees (Celsius) contains more__________ than air at the same temperature.
thermal energy
Any particular location on Earth experiences
two high tides and two low tides each day
Which planet has the longest "day"?
uranus
Which of the following forms of light can be observed with telescopes at sea level?
visible light and radio waves
Within 0.3 AU of the young Sun, rocky material
was present in gaseous form
At what temperature do hydrogen and helium condense?
when taking hydrogen & helium gas & cooling it to an extremely low temperature
Uranus rotates
with an axis tilt that lies nearly in the ecliptic plane.