MasteringAstronomy HW3
Earth-centered, sun-centered, neither or both: a planet beyond Saturn rises in the west and sets in the east
Earth-centered
Stellar parallax exists only because Earth orbits the Sun. Therefore, if the ancient Greeks had measured stellar parallax, they would have known that their belief in an Earth-centered universe was wrong. Why didn't the ancient Greeks measure stellar parallax?
Even for the nearest stars, parallax angles are too small to measure with the naked eye.
A planet beyond Saturn rises in the west, sets in the east
False
We sometimes see a crescent in Jupiter
False
The great contribution of Tycho Brahe was to _________.
observe planetary positions with sufficient accuracy so that Kepler could later use the data to discover the laws of planetary motion
If you wanted to document the apparent retrograde motion of Mars, you would need to measure and record Mars's __________ over a period of __________.
position among the constellations..... several months
Earth-centered, sun-centered, neither or both: We sometimes see a crescent Jupiter
Neither
The Sun-centered system pictured in the lower window of the animation offers a simple explanation for observations of apparent retrograde motion. Should these facts alone have been enough to convince the ancient Greeks that Earth really does go around the Sun?
No, because the Greeks had an Earth-centered model that also accounted for apparent retrograde motion.
Today, astronomers can detect and measure stellar parallax for thousands of the nearest stars, providing us with direct evidence that Earth really does orbit the Sun. Moreover, as the Parallax Angle animation shows, these measurements allow us to calculate distances to these relatively nearby stars. If we hope to use parallax to measure distances to even more-distant stars, which of the following telescopes would be most useful?
A telescope that orbits the Sun in the outer solar system
Earth-centered, sun-centered, neither or both: Moon rises in the east, sets in the west each day
Both
Earth-centered, sun-centered, neither or both: Stars circle daily around the north or south celestial pole
Both
Earth-centered, sun-centered, neither or both: a distant galaxy rises in the east, sets in the west each day
Both
When we see Saturn going through a period of apparent retrograde motion, it means:
Earth is passing Saturn in its orbit, with both planets on the same side of the Sun.
What is really happening in space during the periods when we see Mars going through apparent retrograde motion?
Earth is passing by Mars in its orbit around the Sun
Earth-centered, sun-centered, neither or both: Mercury goes through a full cycle of phases
Sun-centered
Earth-centered, sun-centered, neither or both: positions of nearby stars shift slightly back and forth each year
Sun-centered
How would a star's parallax change as its distance from Earth increases?
The parallax shift decreases as the star's distance from Earth increases.
Consider the hypothetical observation "a planet beyond Saturn rises in west, sets in east." This observation is not consistent with a Sun-centered model, because in this model __________.
The rise and set of all objects depends only on Earth's rotation
A distant galaxy rises in the east, and sets in the west each day
True
Mercury goes through a full cycle of phases
True
Positions of nearby stars shift slightly back and forth each year
True
Stars circle daily around the north or south celestial pole
True
The Moon rises in the east, and sets in the west each day
True
Stellar parallax occurs in much the same way as parallax on Earth, with greater parallax for stars that are nearer. Which statement best summarizes why stellar parallax occurs?
We view nearby stars from different positions in Earth's orbit at different times of year.
Consider a time when Mars is in the middle of one of its periods of apparent retrograde motion. During this time, Mars appears _____ in our night sky and crosses the meridian around _____.
brightest..... midnight
The great contribution of Nicholas Copernicus was to _________.
create a detailed model of our solar system with the Sun rather than the Earth at the center
Based on their inability to detect stellar parallax, the ancient Greeks concluded that _________.
either Earth is the center of the universe, or stars are extremely far away
We never see a crescent Jupiter from Earth because Jupiter __________.
is farther than Earth from the Sun
At most times, Mars appears to move __________ relative to the stars. The exceptions are during its periods of apparent retrograde motion, when Mars appears to move __________ relative to the stars.
left (eastward)..... right (westward)
