Astronomy Chapter 2 – Flashcards
Unlock all answers in this set
Unlock answersquestion
The heliocentric model was actually first proposed by
answer
Aristarchus.
question
Compared to orbital velocity, escape velocity is about:
answer
40% more
question
Given that the planet orbiting the nearby star 51 Pegasi is about 20X larger than the Earth, but 400X more massive, on that world you would weigh:
answer
the same as you do here.
question
Jupiter lies about 5 A.U. from the Sun, so at its distance:
answer
the Sun's gravity is 25 times weaker than its pull on the Earth.
question
Scientists today do not accept the Ptolemaic model because:
answer
the work of Tycho and Kepler showed the heliocentric model was more accurate.
question
The most famous prehistoric astronomical observatory is:
answer
Stonehenge
question
The Law of Universal Gravitation was developed by:
answer
Newton.
question
Galileo found the rotation period of the Sun was approximately
answer
a month.
question
According to Kepler's third law, the square of the planet's period in years is:
answer
proportional to the cube of its semimajor axis in A.U.
question
Which of these was NOT seen telescopically by Galileo?
answer
stellar parallax
question
Kepler's first law worked, where Copernicus' original heliocentric model failed, because Kepler described the orbits as
answer
elliptical, not circular.
question
Combining Newton's and Kepler's laws, we can weigh the Sun, provided we know:
answer
the size of the A.U. and exact length of the year.
question
A circular orbit would have an eccentricity of
answer
0.
question
Which of these was a contribution of Newton to astronomy?
answer
- Artificial satellites could be put into orbit about the Earth. - His differential calculus lets us calculate planetary motions more accurately. - The Sun's gravity is greatest on a planet at perihelion, so the planet must speed up. - The Moon pulls as strongly on us as we do on it. - All of these were due to Newton's work is correct
question
How does Kepler's First Law refine the Copernican model greatly?
answer
Copernicus, like the Greeks, thought all orbits were circular. But when Kepler used elliptical orbits, particularly with Mars and Mercury, the theory fit the actual observations of planetary motion much better than did the old Ptolemaic one.
question
Relate Kepler's Second Law to the speeds of the planets.
answer
In equal time intervals, the lines that connect each of the planets to the sun must all sweep out equal areas. The longer this line, the slower the planet could move and still sweep out this constant area. Thus more distant planets orbit the Sun slower, and each planet will speed up at perihelion and slow down at aphelion.
question
he force of gravity between two objects:
answer
increases with the masses of the bodies, but decreases with the square of the distances between them.
question
Which of these observations of Galileo refuted Ptolemy's epicycles?
answer
the complete cycle of Venus' phases
question
Geosynchronous satellites orbit at about four earth radii, where the earth's gravitational pull is:
answer
1/16 g.
question
Which was a contribution to astronomy made by Copernicus?
answer
He laid out the order and relative motion of the known solar system
question
Which of the following was NOT a contribution of Galileo to astronomy?
answer
The changing appearance of Saturn's rings corresponds to our seasons
question
Which of the statements below is part of both the Ptolemaic and Copernican models?
answer
The Moon orbits the Earth once a month.
question
According to Copernicus, the retrograde motion for Mars must occur
answer
at opposition, when the earth overtakes Mars and passes between Mars and the Sun.
question
The heliocentric model was actually first proposed by:
answer
Aristarchus
question
The most accurate Greek attempt to explain planetary motion was the model of:
answer
Ptolemy
question
Which concept was NOT a part of Kepler's Laws of Planetary Motion?
answer
Epicycles are needed to explain the varying brightnesses of the planets.
question
During the eighteenth and nineteenth centuries, attempts to precisely measure the astronomical unit relied largely on rare:
answer
transits of the inferior planets across the Sun.
question
Which of these was NOT a telescopic discovery of Galileo?
answer
the moons of Saturn
question
What does Kepler's third law imply about planetary motion?
answer
Planets further from the Sun orbit at a slower speed than planets closer to the Sun.
question
Orbital speed is the speed with which a planet moves around the Sun. This speed is determined by
answer
the mass of both the planet and the Sun and the distance between the two.
question
Which of the following is a contribution to astronomy made by Galileo?
answer
- Jupiter has four moons orbiting it. - The Moon has craters, mountain, valleys, and dark flat areas on its surface. - The astronomical telescope can show us far more detail than the eye can. - Venus appears almost fully lit when it lies on the far side of the Sun. - all of the above is correct
question
Which of these was NOT a part of the original Copernican model?
answer
Mercury speeds up at perihelion, and slows down at aphelion.
question
Escape velocity is the speed required to
answer
overcome the gravitational pull of an object
question
The Ptolemaic model probably persisted for all these reasons EXCEPT:
answer
it accounted well for Galileo's observations of the phase cycle of Venus.
question
According to Copernicus, retrograde motion for Venus must occur around
answer
inferior conjunction, when it passes between us and the Sun.
question
A planet whose distance from the Sun is 3 A.U. would have an orbital period of how many Earth-years?
answer
square root of 27
question
Upon which point do Copernicus and Kepler disagree?
answer
The orbits of the planets are ellipses, with one focus at the Sun.
question
The place in a planet's orbit that is closest to the Sun is called
answer
perihelion
question
The principal culture that transferred Greek astronomical knowledge to Renaissance Europe was:
answer
Islamic.
