ChatterBank3 mins ago
The North Star.
What is the story with the North Star. During the winter it can be found by following a line straight up from the two stars at the end of The Big Dipper, but is this the case all year round? I looked up tonight and there doesn't seem to be a star there. Will it come into view soon? Is it the case that it can only be seen during winter or is it there all year and only lined up with the Big Dipper during winter? Does anyone know?
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Yes it can be seen all year round.
Yes it is always on a line from the 'pointers' in Ursa Major (Big Dipper).
The position of the stars relative to each other does not change from month to month (at least, not by an amount that you will notice). The stars will appear to rotate about the pole star during the year, but that is not because the stars move, but because the earth rotates about the sun.
The pole star will always be in the north and at the same elevation when viewed from the same location regardless of month.
Yes it is always on a line from the 'pointers' in Ursa Major (Big Dipper).
The position of the stars relative to each other does not change from month to month (at least, not by an amount that you will notice). The stars will appear to rotate about the pole star during the year, but that is not because the stars move, but because the earth rotates about the sun.
The pole star will always be in the north and at the same elevation when viewed from the same location regardless of month.
Polaris remains within <1 degree of a line extending above the Earths northern axis of rotation, (north pole) day and night, all year long.
http://www.wainscoat....onomy/cfht-trails.jpg
The Big and Little Dippers rotate around Polaris completing a circle in just under one 24 hour period. From one night to the next a given star will advance in position just under one degree when viewed at the same time each night accumulating ~30 degrees of westward progress in one month and appearing in a position opposite to Polaris in six months.
In sum, the Earth turns beneath the celestial sphere a total of ~366.25 rotations in one year, having completed its annual journey around the Sun in ~365.25 days.
http://burro.cwru.edu...ig_Dipper_Seasons.jpg
http://www.wainscoat....onomy/cfht-trails.jpg
The Big and Little Dippers rotate around Polaris completing a circle in just under one 24 hour period. From one night to the next a given star will advance in position just under one degree when viewed at the same time each night accumulating ~30 degrees of westward progress in one month and appearing in a position opposite to Polaris in six months.
In sum, the Earth turns beneath the celestial sphere a total of ~366.25 rotations in one year, having completed its annual journey around the Sun in ~365.25 days.
http://burro.cwru.edu...ig_Dipper_Seasons.jpg
Generally speaking stars don't move much in relation to each other their distance is so far that what is called their "proper motion" is too small to be noticable.
A few of the closer ones appear to move a tiny amount over the year due to the Earth's change in position they exhibit "paralax". This is pretty small but it can be measured and it's how we calculate how far away they are.
There ae exceptions - check out Barnard's Star this is a celestial Greyhound it has a very large proper motion and on professional charts is marked as a line with a date indicating where it will be as the years pass
A few of the closer ones appear to move a tiny amount over the year due to the Earth's change in position they exhibit "paralax". This is pretty small but it can be measured and it's how we calculate how far away they are.
There ae exceptions - check out Barnard's Star this is a celestial Greyhound it has a very large proper motion and on professional charts is marked as a line with a date indicating where it will be as the years pass
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