ROUND 8 - SCIENCE: 9 Planets from Outer Space

We realize that there is some debate as to what exactly should be
called a planet, but for purposes of this round the usual list
of 9 planets in our Solar System will apply.  As there will be
10 questions, you shouldn't be surprised to hear that some answers
will repeat.

 1. On which planet is the length of a day most similar to ours?

	Mars


 2. Which planet's orbit takes it closer to the Earth than any other?

	Venus


 3. Which was the first planet discovered using a telescope?  By
    "discovered" we mean that it was recognized to be a planet.

	Uranus
    

 4. Which planet was discovered by using a telescope to photograph
    the same part of the sky on different nights, then using a
    Blink-Comparator to look for differences between the two
    photographic plates?

	Pluto


 5. The four largest planets in the Solar System are called the gas
    giants.  Name all four.

	Jupiter, Saturn, Uranus, Neptune


 6. There are also four planets in the Solar System now known to have
    rings around them.  Name any two.

	Jupiter, Saturn, Uranus, Neptune


 7. Seven of the nine planets have at least one satellite, or moon.
    Name the two that do not.

	Mercury, Venus


 8. This was the first planet known to have more than one satellite
    (or moon) orbiting it, and in 2001 it again became the planet with
    the greatest number of known satellites.  Name it.

	Jupiter

 
 9. Three planets exhibit retrograde rotation.  This means that the
    pole from which the planet would be seen to rotate anticlockwise,
    like the North Pole on Earth, is on the south side of the planet's
    orbital plane as seen from the sun.  Name any one of the three.
    
 	Venus, Uranus, Pluto


10. The orbits of the planets are ellipses, but they vary in what
    is called eccentricity; that is, in how far they differ from an
    exactly circular orbit.  Name any one of the three planets with
    the most eccentric orbits (that is, the least circular).

	Mercury, Mars, Pluto