Newsletter

NOVEMBER ANSWERS

1) What is the brightest star in the sky apart from the Sun?

Sirius in Canis Major is the brightest star. For details and where to find it see the article about
Orion in this issue.

2) What are the dark areas on the Moon called?

The dark areas are called "Mare" which is the Latin word for seas. The first people to look at
the Moon through telescopes saw the large flat areas and thought they actually were bodies
of water. Now we know these Mare are ancient lava flows that spread over the surface when
the Moon was younger covering the rougher ground.

3) What is the diameter of the Sun?

The diameter of the Sun is 1,393,000 kilometres. Compare that with the Earth's diameter of
12,756 kilometres.

4) What is the "Big Bang"?

The Big Bang is that event in which our universe came into existence. It was the beginning
of space and time, matter and energy. At the initial instant the universe was infinitely hot
and infinitely dense and began to expand and cool. The most recent evidence indicates
that the Big Bang occurred 13.7 billion years ago.

HEADACHE ANSWER.

The Earth rotates once on it's axis in 23 hours 56 minutes so any star will return to the
same point in the sky every 23 hours 56 minutes. Because the Earth is in orbit around
the Sun, the Sun will appear to move in relation to the stars. The movement is such that
it takes 24 hours for the Sun to return to the same point in the sky, four minutes a day
more than it takes the stars. The stars appear to move in relation to the Sun (although
it is actually the Sun that moves in relation to the stars) and that is why different stars
appear in the night sky at different times of the year. The stars will take a year to move
around the sky and return to the same point.