Question

Do constellation move around if you observe them at the same time?

If you will observe one constellation over the course of three weeks at the same time with 4 days interval - will you see the constellations always in the same place or will the move around?

Answer 1

The movement if individual stars inside a constellation takes many years to see any change.

Explanation:

But if you look at the north pole the circumpolar constellation move in a circle..This is due to rotation of Earth. picture credit Anglo Australian observatory.

Answer 2

The constellations move due to the earth's rotation and orbit and due to the motions of the stars themselves.

Explanation:

The positions of the constellations and their individual stars depends on viewing time and how long the observations are taken over. There are three factors affecting their positions.

The first is the rotation of the Earth. Constellations to the North in the Northern hemisphere and to the South in the Southern hemisphere rotate during the course of the night.

Constellations nearer the equator will only be visible for part of the night. Some will disappear over the horizon, others will appear from the horizon.

The second factor is the season. Constellations which are in the direction of the Sun as seen from Earth are not visible during the day. That is why some constellations are only visible in certain seasons. The Summer sky is very different to the Winter sky.

Some constellations are only visible from the Northern hemisphere and some are only visible from the Southern hemisphere.

The third factor is that constellations are arbitrary groupings of stars which appear to form a pattern. The individual stars will be at very different distances from the Earth. Take for example the constellation of Centaurus. The nearest star in the constellation `alpha` Centauri is the closest star at just over 4 light years away. Other stars in Centaurus are over 600 light years away.

As a consequence of the distances of the stars being different, over longer periods of time the constellations will change shape and position due to the motions of the stars within the galaxy. This effect won't be visible over a matter of weeks as it takes a long time for the relative positions of stars to change.