Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Loot van Tonder on 18/05/2010 09:30:02

Title: If we orbit the sun, shouldn't stars become more faint?
Post by: Loot van Tonder on 18/05/2010 09:30:02
Loot van Tonder  asked the Naked Scientists:
Hello Chris,
Can you please explain to me the route earth rotates around the sun.
Q:  If we rotate around the sun, in 6 months' time we should not see our own Southern Cross (daylight), yet we do.
Q:  If we move away from stars, shouldn't they become fainter?
The way I see it, we are not moving on a horizontal plane, but on a vertical plane with not a very big arc at all around the sun because in a 12 hour period we see the same stars at 7 to 10 deg. difference.  Please explain. 
Loot van Tonder.

What do you think?
Title: If we orbit the sun, shouldn't stars become more faint?
Post by: Soul Surfer on 18/05/2010 16:31:49
THe first point is that that the stars are similar to our sun and therefore because of their brightness a very long way away.  we are 8 light minutes away from the sun but the nearest star is four light years away from us and most visible stars are many tens or hundreds of light years away.  the tiny movement of the earth does not make any noticeable difference to the brightness but it does make tiny changes to the precise position in the sky that a star occupies and this can be measured for the nearer stars and used to determine their distance.

As far as the movement of the stars is concerned like the globe of the earth the stars form a sphere which we can see about half of at any time during the night from the point of view of any location on the earth's surface the star rotate around the pole either the north pole or the south pole depending on which hemisphere you live  (you are using a south polar description involving the southern cross)  and there are usually some stars which are circumpolar and always visible at night.  however there are some stars that you will never see.  For you this may include the great bear or plough which is a circumpolar constellation where I live because living in the northern hemisphere I never see the southern cross.
Title: If we orbit the sun, shouldn't stars become more faint?
Post by: tommya300 on 18/05/2010 21:44:25
Is it safe to say using the North Star to navigate, I can get lost if I were in Australia!
It has been mentioned that the north Star (Polaris) can be seen from the equator depending on the surrounding terrain...
I Think this is because of the affect the atmosphereic refraction of light.