MasteringAstronomy Assignment #9

Sorting Task: Comets, Meteors, and Asteroids
Part A
Listed following are some distinguishing characteristics of comets, meteors, and asteroids. Match these to the appropriate category of objects.

Visual Activity Exploring the Formation of Comet Structures
A comet entering the inner solar system from afar will __________.
form a coma and some time later form a tail

During the time that a comet passes through the inner solar system, the comet can appear quite bright because __________.
sunlight reflects off the comet’s tail and coma

A comet’s plasma tail always points directly away from the Sun because __________.
of pressure exerted by the fast-moving charged particles in the solar wind


Vocabulary in Context: Comets
Part A
Match the words in the left-hand column to the appropriate blank in the sentences in the right-hand column. Use each word only once.

Ranking Task: Basic Properties of Extrasolar Planets
Part A
The following images show four identical Sun-like stars and their companion planets, all traveling in circular orbits. In each case, the mass of the planet is given in Jupiter masses and the orbital distance is given in Astronomical Units (AU). Rank each case based on the strength of the gravitational force exerted by the extrasolar planet on its central star, from weakest to strongest. If you think that two (or more) diagrams should be ranked as equal, drag one on top of the other(s) to show this equality. (Not to scale)

Part B
The following figures show four identical Sun-like stars and their companion planets. Each planet’s orbital distance is given in Astronomical Units (AU); note that in this case, all four planets have the same mass. Rank the extrasolar planets based on the amount of time it takes each to complete one orbit, from shortest to longest. (Not to scale)

Part C
The following images show the set of four stars and planets as in Part B. Imagine that an Earth-based observer could see the motion of each of the stars edge-on. Rank each star based on the amount of Doppler shift we’d see in its spectrum as it moves in response to the gravitational tug of its planet, from smallest to largest. (Not to scale)

Ranking Task: Velocity Curves for Stars with a Single Orbiting Planet
Part A
The following four graphs show the velocities, toward and away from Earth, of four identical stars. Assume that all four stars have extrasolar planets orbiting them at the same distance, and that the velocities are inferred by measuring Doppler shifts in the spectra of the stars. Rank the graphs from left to right based on the amount of orbital Doppler shift observed in each star’s spectrum, from smallest to largest.

Part B
The following four graphs show the velocities, toward and away from Earth, of four identical stars (the same graphs shown in Part A). Assume that all four stars have extrasolar planets orbiting them at the same distance. Rank the graphs from left to right based on the amount of time that it takes the extrasolar planet orbiting each star to complete one orbit, from shortest to longest. If you think that two (or more) of the graphs should be ranked as equal, drag one on top of the other(s) to show this equality.

Part C
The following four graphs show the velocities, toward and away from Earth, of four identical stars (the same graphs shown in Parts A and B). Assume that all four identical stars have extrasolar planets orbiting them at the same distance. Rank the graphs from left to right based on the mass of the extrasolar planet that orbits the star, from smallest to largest.

Visual Activity: Measuring Properties of Extrasolar Planets
Which of the following properties can be inferred from the star’s orbital period?
the planet’s orbital radius

Is it possible to determine the planet's mass from the star's velocity curve?
yes, by measuring both the star's orbital period and its change in velocity over the orbit

Consider the planet that causes the stellar motion shown in Plot 2 (be sure you have clicked the “Plot 2” button in the lower window of the animation). What can be said about a different planet orbiting the same star with an orbital period of 500 days?
The planet must be closer to the star.

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What is the most important defining property of the Trojan asteroids?
They orbit the Sun in the same path as Jupiter and 60° ahead of and behind it.

Which of the following characterizes the Kuiper belt?
It is a disk-like region between the outer planets and the Oort cloud.

The ingredients of a typical comet's nucleus are most likely ________.
dust and rocky particles trapped in methane, ammonia, and water ice

How was Pluto discovered?
It was simple luck and hard work.

Which of the following is NOT one of the criteria necessary to classify an object as a major planet?
It must have at least one moon orbiting around it.

What is the source of the material of a meteor shower?
Comets

The most common type of meteorite to strike Earth is ________.
rocky

Planetesimals were created through what process?
accretion

Which of the following objects is NOT best explained by some sort of unique impact event?
The asteroid belt

Which of the following methods have astronomers used to detect extrasolar planets?
Extrasolar planets have been detected using all of the methods listed here.

Planetary transits, coupled with radial velocity measurements, CANNOT unambiguously tell us which of the following about an extrasolar planet?
The planet's composition

If we lived in a solar system outside of our own, would we be able to detect Earth using Doppler measurements of our Sun's "wobble"?
No. The Doppler shifts would be too small for us to detect.

What is a "hot Jupiter?"
A planet with Jupiter's mass orbiting very close to its star.

What is a brown dwarf?
An object with more mass than Jupiter, but not enough mass to become a star.

What is a the best explanation for the hot Jupiters?
They formed far from their stars, and “migrated†inward because of interactions with the gas disk from which they formed.