Re: Why can you see some stars, and not others at certain times of the year?

Dear Andrew,

Thank you for your question. In order to answer it, it is easier to imagine the stars as a sphere if fixed points outside the solar system, centred on the Sun, much as the ancients saw them. Remember that the Earth goes around the Sun once a year, but the stars stay fixed and do not move.

At midday on August 1st the Sun is directly infront of you. The stars on the opposite side of the sphere are blocked out by the light from the Sun. Later that day, at midnight, the Sun is behind the Earth, and you can see the stars on the other side of the sphere. Six months later, on the 1st February, the Earth is around the other side of the Sun, so the situation is reversed. The stars that were previuosly blocked by the sun light are now behind the Earth, and so can be seen at night. The stars that could be seen at night in August are now 'up' during the day, and so cannot be seen as the Sun is too bright.

I hope this helps

Sarah