Solar System

* The Sun is a low mass star on the outer reaches of the Milky
Way galaxy.
  * The Sun is some 30,000 light years from the center of the Milky
Way and lies on one of the spiral arms.
  * The Sun looks like a burning ball of fire, but it actually has an
internal structure. The visible surface we can see is called the
photosphere and heats up to a temperature of about 6,000 degrees.
  * The mass of the Sun accounts for 99.8% of the mass of the Solar
System.   And most of that final 0.2% comes from Jupiter. So
the mass of the Earth is a fraction of a fraction of the mass
of the Solar System.

  * Mercury is so close to the Sun, and it’s baking hot. But the
reality is that there are regions on the surface of Mercury which
are never heated by the Sun.
  * Mercury is actually a difficult planet to observe. Because it orbits
closer to the Sun than the Earth, it appears to stick close to the
Sun in the sky. The only times you can actually observe it is when
the Sun has just set, or is about to rise.
  * Mercury is so small that it has too little gravity to hold an
atmosphere like Earth or Venus. But it does have a tenuous
atmosphere of hydrogen, helium, oxygen, sodium, calcium and
potassium around it.
  * The Hubble Space Telescope has never been used to observe
Mercury, and it never will be. The planet is so close to the Sun that
the light from the Sun would overwhelm Hubble, and could
permanently damage its optics and electronics.

  * Venus rotates very slowly. While a day on Earth takes just 24 hours to
complete, a day on Venus is 243 of our Earth days.
  * Venus just looks like a really bright star in the sky, if you can see it
with a telescope, you’ll see something much different. When looking
through a telescope, you can see that Venus goes through phases,
like the Moon.
  * The size of Venus is only 650 km less than the size of Earth, and the
mass of Venus is 81.5% the mass of the Earth.
  * The... [continues]

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