Astronomy: Planetary Motion, Eclipses, and Spectral Lines

for ast 103 exam 1

When do planets move at their fastest speed?

When they're closest to the sun

The best test of a scientific theory is how…

well it predicts new observations

The apparent retrograde motion of Jupiter is caused by the

real motion of Jupiter along its epicycle

A rock is in circular orbit about the Sun with a radius 4 AU. What is its period?

8 years

An asteroid is in circular orbit 3 AU from the sun. Its period of revolution is how many years?

sqr rt of 27

If Earth's orbit around the Sun were twice as large as it is now, the orbit would take

More than two times longer to traverse

What causes the Moon's phases?

As the Moon orbits the Earth, the part of the Moon that is lit is a changing fraction of the part that faces the Earth.

What causes the Moon's phases?

As the Moon orbits the Earth, the part of the Moon that is lit is a changing fraction of the part that faces the Earth.

Can one ever observe an annular eclipse of the moon? Why or why not?

One can never see an annular eclipse of the Moon, because the Moon is smaller than the Earth's shadow at the position of the Moon.