astro-101 exam 2

Gas giants decrease in size with increased distance from the Sun because the Solar Nebula was less dense farther out.

Study the sizes of the gas giants shown in the image above (the distance from the Sun increases from left to right), and choose the best explanation that accounts for their differences in size.

If light has finite speed, it would take longer for it to travel from Jupiter to Earth when Earth is farther from Jupiter.If light has infinite speed, an eclipse would be seen to happen at the same time regardless of how far away Earth is from Jupiter.

Following the invention of the telescope, astronomers were able to measure the speed of light by observing Jupiter's moons passing behind Jupiter in their orbit and becoming eclipsed. Study the figure, which shows how someone on Earth can view Jupiter's moon's eclipses when Earth is closer to or farther from Jupiter, and determine which of the following are correct.

The presence of dark lines at specific wavelengths in an otherwise continuous spectrum can be explained most easily by which of the following?

A cool gas between observer and source is absorbing light at the wavelengths corresponding to the missing photons.

Comparing objects in a related group can reveal patterns among them. These patterns in turn can help us learn more about those objects than we could by studying each individually.With this goal in mind, watch the Introduction of the AstroTour Animation on Solar System Formation. Pay attention to the animation of the planets in the Solar System and select all of the following choices that describe the patterns that you've observed. As you do so, think about the implications of how the Solar System may have formed.

All planets orbit the sun in a rougly flat plane, All planets orbit the Sun in the same direction, The orbits of the outer planets (those most distant from the Sun) are spaced farther apart from one another than the orbits of the inner planets, The closest planets to the Sun are much smaller than the planets that are farther away.

The cloud will spin faster

Based on the law of conservation of angular momentum, what would happen to a collapsing cloud of gas and dust--isolated in space with no external forces--as its size decreases?

radio, infrared, orange, green, ultraviolet, gamma ray

Changing the wavelength of visible light changes its color. If the wavelength is decreased or increased outside of the range of wavelengths our eyes can detect, the light becomes invisible to us, but it is still fundamentally light. Examine the figure, which shows the entire electromagnetic spectrum and includes all types of light as a function of wavelength. Given what you learned from the figure, rank these types of light in order of increasing energy.

composition

Comets that visit the inner Solar System were kicked there from the Kuiper Belt or Oort Cloud by gravitational close encounters with other objects. Pluto travels through the inner edge of the Kuiper Belt. As Ceres is just a large asteroid, could Pluto be just a large Kuiper Belt comet nucleus? Which of the following properties of Pluto would best help answer this question?

Star I is observed to be brighter than Star II. Which of the following is/are true?

If their luminosity is the same, Star I must be closer. Star II may be bigger than Star I. If they are the same size and distance from the observer, Star I is hotter.

There would be a noticeable delay in communications at the speed of light between Earth and astronauts on the Moon. If the light of the Sun were suddenly extinguished, we wouldn't notice it from Earth for over 8 minutes. When we gaze at the Andromeda Galaxy, we are looking back in time to the way it used to appear millions of years ago.

In a vacuum, light travels 300,000 km every second. Examine the following figure, which shows how long it takes for light to travel particular distances, and then scroll down to the question at the end. Based on the time frames given in the above figure, which of the following are implications of the finite speed of light?

Pluto was reclassified from planet to dwarf planet in 2006. Which of the following is an official criterion for being called a planet that is not met by Pluto?

It has gravitationally cleared the neighborhood around its orbit

A typical amateur telescope is a 10-inch reflector (where "10-inch" refers to the diameter of the telescope's mirror). How does the light-gathering power of the Hooker 100-inch reflector on Mount Wilson compare with that of the amateur telescope?

It is 100× greater.

A spectrum of a distant object reveals a sequence of known absorption lines that are all shifted to shorter wavelengths. What can be concluded about the object?

It must be moving toward us.

At least 75% of asteroids are primordial C-type. What does this imply about how the asteroid belt was formed?

It was formed mostly from pieces of planetesimals that were prevented from getting large enough to differentiate, but it also contains some pieces of objects that were large enough to differentiate and were later shattered.

An object is moving with a given speed anddirection. If a net force acts on it in the oppositedirection it is moving, what will happen?

It will slow down.

The resolution of radio telescopes suffers greatly from the large wavelengths of the light they are observing. What can be done to a radio telescope to improve its angular resolution?

Make its dish bigger.

the composition of any gas between the light-emitting "surface" of the star and the observer

Observations of excited gas in the lab show that every element, molecule, and ion has its own unique set of possible electron energy levels, as shown in the emission spectra below. Based on this fact, what can we find from the wavelengths of absorption lines seen in the spectrum of a star?

We all have mass because we are made frommatter. What gravitational force do we mostoften interact with most strongly?

Our weight, which is a measure of thegravitational force between us and Earth.

Comets are planetesimals made of rock and ice that become visible to us when their ice sublimates at the closest approach to the Sun, making them glow brightly and grow tails. Where do they come from? We can answer that question by studying the orbits of the comets that pass close enough to us that we can observe them. We see two distinct types of orbits: short-period and long-period comets. Watch the following AstroTour animation, and choose the answer below that most likely follows from your observations.

Short-period comets come from some location near the ecliptic plane of the Solar System, and long-period comets come from farther away, with random directions in a spherical distribution around the Sun.

Individual particles in the nebula stick together to form larger pieces which later collide with and stick to other pieces to gradually form larger objects, which eventually grow to the size of a planet.

Study this picture of a meteorite that has been sliced open to show its interior, and use your observations to determine the most likely formation scenario for a planet.

X-ray, infrared at 100 micrometer (10-⁴ m), ultraviolet at 100 nm, gamma ray

The atmosphere absorbs some light before it can reach a telescope's detector, making objects appear fainter. The exact amount of absorption depends on the wavelength of light being observed, as shown in this graph of the percentage of light that can make it through the atmosphere to the ground. 0% transparency (atmosphere is opaque) means no light gets through, and 100% transparency means all the light gets through. The type of light per wavelength is labeled at the bottom of the figure. Visible light is marked by the rainbow. Based on the above graph, which of these types of light from astronomical sources are not observable from the ground?

M-Type, S-Type

The majority of asteroids exist in the asteroid belt between Jupiter and Mars. Why would that be the case? There are two main possibilities: There used to be a planet there that was destroyed in a giant impact, or the planetesimals there were somehow prevented from forming a planet in the first place. To figure out which of these is correct, we can look at spectra to determine the composition of the asteroids themselves and study actual samples of asteroids that fell to Earth—that is, meteorites. The figure below explains the difference between the types of asteroids and meteorites. Based on the figure, which asteroid types would be more common if they were the result of a shattered planet?

Why do stars twinkle?

The motion of Earth's atmosphere creates the appearance of twinkling.

The frequency of the light would decrease. The energy of the light would decrease.

The nature of light is rather unique: It acts like both a particle (called a photon) and a wave that can propagate energy even through empty space. Navigate to the interactive figure in Section 2 of this animation, as shown below, to see how changing the amplitude, wavelength, speed, and frequency of a light wave affects its properties. Choose all of the effects that would automatically happen if the wavelength of light were increased.

Compare the spectra of blackbodies with different temperatures. Which of the following is true?

The peak of the emission in the spectrum of the cooler object is at a longer wavelength

Space telescopes that exist in orbit above most of Earth's atmosphere are expensive, so they must therefore be supported with a very compelling motivation. If you were trying to justify funding for a space telescope in orbit around the Earth, which of the following would be the best argument to use?

The telescope could observe wavelengths of light that are not visible from the ground.

A rocky object with a diameter of 10 cm is found lying atop otherwise untouched Antarctic ice. It is determined to have originated from space. Therefore the rock is

a meteorite.

Larger lenses in telescopes offer better resolution. Resolution is defined as the closest angular distance two objects can be apart from one another before their light merges together and they look like just one object. Therefore, smaller resolutions are better (closer objects can be separated). The resolution of the human eye is 1 arcminute, or 1/60th of a degree. If the light of two street lamps in the distance is separated by 0.5 arcminute, what will you see with your eyes?

a single light, with the combined brightness of each street lamp

If a kilogram of iron is dropped at the same timeas a kilogram of feathers, the iron will reach theground first. Why is that so?

because other forces in addition to gravity,such as air resistance, can affect a fallingobject

Detailed observations of a long-period comet, near aphelion, would most likely not include which of the following?

coma, jets, ion tail, dust tail

If a planet orbits the Sun in an exactly circular orbit, its speed is _____ and its velocity is_____

constant, changing

Using the interactive, move the planet size and star size sliders. Rank the following planet and star sizes in order of the largest depth created.

deepest eclipse to shallower eclipse large planet, small star small planet, small star small planet, large star

Using technology similar to that available on Earth today, a distant alien astronomer searching for evidence of planets around the Sun is likely to be most successful with which of the following?

detection of Jupiter via the radial velocity method

Which of the following would you expect to differ significantly between a long-period comet and an asteroid?

distance at aphelion, inclination of orbit, distance between the point of origin and the Sun, albedo at perihelion

dwarf

planet, dwarf planet, or not a planet or a dwarf

not a planet or a dwarf

planet, dwarf planet, or not a planet or a dwarf

planet

planet, dwarf planet, or not a planet or a dwarf

Arrange the following regions of the electromagnetic spectrum from lowest to highest frequency.

radio, infrared, optical, ultraviolet, x-ray, gamma rays

Which of the following can astronomers determine directly from the spectrum of an object?

speed toward or away from an observer, composition, temperature

A ball is swung about your head using anattached rope. What is the source of thecentripetal force?

tension in the rope

Observations yield radius and mass measurments for an exoplanet. Which of the following properties can be determined from these two quantities?

whether or not the planet is a gas giant, the planet's density