Short Questions about the Solar System
- The solar system rotates quite fast with all the planets going
around the sun on time scales of years. The clouds of gas and dust we
see in the galaxy that are probably going to form new solar systems are
rotating so slowly we can barely detect it but we are sure they are
rotating a little bit. Describe how the change to fast rotation
probably occurred as our solar system was being formed. You may wish
to use the analogy of a spinning figure skater or a child moving on a
- There appears to be little in the way of junk left in the solar
system within the orbits of the giant gas planets except the asteroid
belt. By junk I mean other asteroids, mini-planets or mountainous
chunks of ice similar to comets. From the craters on the moon and
elsewhere we think that there was probably a lot of junk around in the
early solar system. Describe what we think happened to any junk that
didn't hit something directly.
- Historically astronomy was limited to visible light; meaning
light we can see with our eyes.
Visible light is still particularly important
for astronomers on the ground even though we have electronics that can detect
all sorts of other wavelengths of light we cannot see with our eyes.
What is it about Earth's atmosphere that makes visible light more useful
than most other wavelengths of light for astronomers on the ground?
Note: The answer you give should have nothing to do with whether we can see particular
type of light using our eyes.
- Brightness and Radar measurements. Suppose we have a radar
dish that generates a strong signal that travels out to hit an
asteroid 109 kilometres away.
(a) How would the brightness of the radar signal arriving at the asteroid
change if the asteroid was moved twice as far away?
(b) How would the brightness of a signal originating at the asteroid and detected back on Earth vary if the asteroid was moved twice as far away?
(c) In the radar experiment the asteroid reflects that part of radar
signal that arrives at it back in all directions. In this way it is
behaving like a weak source of radar signals. The part of the signal
comes back to the original radar has a brightness of 81. The lowest
signal we can detect has a brightness of 1. Determine the way the
strength of the detected signal varies with the distance that
the asteroid is away from the radar dish. What is the furthest an
asteroid of the same size and other characteristics could be away from
us before we could no longer use this radar equipment to measure the
distance to it?
- Examine the table. Which planets would float if you dropped them in the Sun? Which would float if you dropped them in water? Which would sink fastest?
- How many sets of planets would you need to create the mass of the Sun?
- What do the orbits of the planets and satellites tell us about the rotation of the cloud that formed the solar system?
- The speed of light is 300,000 kilometres per second. This number
isn't easy to get a feel for but it's good it's so fast because it allows
us to see things instantly on Earth without waiting for the light to arrive.
The Sun is far enough away that
light takes an appreciable time to travel to us. Assuming the sun is
150,000,000 kilometres away, how long would it take us to realize
if the sun suddenly stopped shining?