Chapter 1 Quiz AST2002

Johannes Kepler used decades of Tycho Brahe's observational data to formulate an accurate description of planetary motion. Kepler spent almost 30 years of his life trying to develop a simple description of planetary motion based on a heliocentric model that fit Tycho's data. What conclusion did Kepler eventually come to that revolutionized the heliocentric model of the solar system?

Kepler determined that the planetary orbits are elliptical

What two measurable properties directly tell us the size and shape of a planet's orbit?

Semimajor axis and eccentricty

Kepler's second law of planetary motion states that a planet in orbit around the Sun will do which of the following?

Sweep out equal areas in equal times

A major flaw in Copernicus's model was that it still had

Circular orbits

An accurate sketch of Mars's orbit around the Sun would show

A nearly perfect circle

Copernicus proposed a heliocentric model for the solar system primarily because

It was much simpler than the Ptolemaic model

An asteroid with an orbit lying entirely inside Earth's

Has an orbital semimajor axis of less than 1 AU

Galileo Galilei was the first scientist to perform experiments in order to test his ideas. He was also the first astronomer to systematically observe the skies with a telescope. Galileo made four key observations that challenged the widely accepted philosophical beliefs on which the geocentric model was based, thus providing support for the heliocentric model. From the following list of observations, which are the key observations made by Galileo that challenged widespread philosophical beliefs about the solar system?

Jupiter has orbiting moons The Moon has mountains, valleys, and craters The Sun has sunspots and rotates on its axis Venus goes through a full set of phases

Astronomers have made many observations since the days of Galileo and Kepler to confirm that the Sun really is at the center of the solar system, and that the planets revolve around the Sun in elliptical orbits. Which observation(s) could you make today that Galileo and Kepler could not have made to confirm that the heliocentric model is correct?

Stellar parallax in nearby stars Transit of an extrasolar planet Doppler shifts in stellar spectra of nearby stars

The following diagrams are the same as those from Part A. This time, rank the pairs from left to right based on the size of the acceleration the asteroid on the left would have due to the gravitational force exerted on it by the object on the right, from largest to smallest.

Sun (Largest Acceleration) Earth Moon Asteroid Hydrogen Atom (Smallest Acceleration)

The following diagrams are the same as those from Part A. Again considering only the two objects shown in each pair, this time rank the strength, from strongest to weakest, of the gravitational force acting on the object on the right.

Sun (Strongest) Earth Moon Asteroid Hydrogen Atom (Weakest)

The following five diagrams show pairs of astronomical objects that are all separated by the same distance d. Assume the asteroids are all identical and relatively small, just a few kilometers across. Considering only the two objects shown in each pair, rank the strength, from strongest to weakest, of the gravitational force acting on the asteroid on the left.

Sun (Strongest) Earth Moon Asteroid Hydrogen Atom (Weakest)

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