Astronomy Chapter 2

As observed from Earth, the motion of a planet known as direct or prograde motion refers to:

a slow eastward motion against the background stars.

Scientists consider mathematics to be essential to science. The MOST important role of mathematics in science is to:

allow theories to make precise, testable predictions.

One problem with Copernicus's model for the solar system stemmed from his assumption that the orbits of the planets were _____, a flaw that held back the further establishment of his model for some decades after his death.

circular

Consider an unknown object was discovered in the night sky. After astronomers observe this object shift its position relative to the background stars over the course of a night, they can conclude that the object is relatively _____ to Earth.

close

What phase of Venus would be observed at its point of greatest elongation?

cresent

The eastern elongation of Mercury's orbit:

depends both on Mercury's position in its orbit and on Earth's position in its orbit.

Which of these observations did Galileo NOT make using his telescopes?

first clear view of rings from saturn

In the geocentric model of the solar system, only the _____ phase of Venus should be visible from Earth.

full

Which configuration would be the MOST ideal time to observe Venus or Mercury?

greatest elongation

A planet moving in an ellipse with the Sun at one focus will have a speed that is:

highest when it is closest to the Sun.

The very successful Ptolemaic model to describe and predict the apparent motions of planets, assuming them to orbit Earth, had each planet:

moving in a small circle, the center of which was moving around Earth more slowly in a larger circle.

Which configuration would be the MOST ideal time to observe Mars, Jupiter, or Saturn?

opposition

Retrograde motion is an observed feature of the planets. It was explained in the Ptolemaic model of the solar system by having planets:

orbit Earth in small circles moving on larger circles.

What do astronomers call the point of closest approach to the Sun for any planet?

perihelion

The observation by Tycho Brahe of a bright "new star" in 1572 was significant because it:

showed almost no parallax (apparent relative motion), which proved it to be more distant than the Moon.

In Ptolemy's description of the solar system, an epicycle is a:

small circle around which a planet moves while the center of the epicycle follows a large circle around Earth.

When Venus is at _____ conjunction, the Sun is between Earth and Venus.

superior

When three objects are precisely in a straight line, such as the Sun, Earth, and Venus, those three objects are said to be in _____.

syzygy

According to Kepler's third law, an asteroid orbiting the Sun in a circular orbit at half Earth's distance from the Sun would have a sidereal period of:

0.35 years.

Tycho Brahe was one of the last major naked-eye observers in history, still making observations before the advent of the telescope. Yet he was still able to make the most accurate measurements of astronomical objects up to that time, recording the position of the planets with a resolution of _____.

1 arcminute

According to Kepler's third law, an asteroid orbiting the Sun in a circular orbit at twice Earth's distance from the Sun would have a sidereal period of:

2.8 years

The angle of greatest elongation for Mercury is about _____.

28 degrees

What would be the distance to the nearest star Proxima Centauri if it is 4.2 light-years from Earth?

4.0 x 1013 km

How did Tycho Brahe prove that the heavens are NOT permanent and unalterable?

A "new star" appeared in the sky, and he showed that the star exhibited no measurable parallax over the course of a night, due to the rotation of Earth around its axis.

Kepler's concept of "equal areas in equal _____" describes how the speed of a planet increases as it nears the Sun.

times

Retrograde motion:

would be seen for Earth if viewed from Jupiter.

If an object of mass m has a speed v, its kinetic energy is given by:

½mv2.

How did astronomer's scientific understanding of gravitational waves evolve over time?

Einstein's theory of general relativity first predicted the existence of gravitational waves, but the waves weren't observed until 2015.

The Roman Catholic Church condemned _____ and placed him under house arrest in the later years of his life for suspicion of heresy, stemming from his observations that refuted the old ideas of Aristotle and Plato.

Galileo

What was one major benefit that Ptolemy's epicycle model of the solar system had over previous geocentric models?

It explained why the planets appeared brighter during retrograde motion.

What is the one standard that makes a scientific theory different from the ordinary, everyday concept of a theory?

It must be testable and falsifiable.

Consider a car driving around a circular track at a constant rate of speed. The car hits a slick spot in the road and the tires of the car lose contact with the road. What happens to the car in the moments after?

It slides in a straight line along the last direction it was traveling before losing contact with the road.

Further observations of the moons of Jupiter confirmed that _____ laws apply not just to planets orbiting around the Sun, but to any objects orbiting another as a result of gravitational attraction.

Kepler's

How does retrograde motion affect the rising and setting of the planets on a given night?

Retrograde motion has no effect, because the diurnal motion is much faster than the planetary motions with respect to the stars. Hence the planets always rise in the east and set in the west.

What condition describes the position of greatest elongation for an inferior planet in the solar system? (Drawing a sketch diagram might be useful.)

The angle between the Earth-planet line and planet-Sun line is 90 degrees.

When Johannes Kepler was young, he worked as an assistant to:

Tycho Brahe.

One proof of Galileo that the Copernican model of the solar system is correct was that:

Venus goes through phases like the Moon.