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Daily Motion of Stars in the Southern Hemisphere

Introduction

Here we explain that the observed daily motion of the stars varies depending on the observer's latitude

The motions of the stars across the sky as viewed from the North Pole and the Equator are quite different. Additionally, depending on observing latitude, certain stars will not be visible. With the aid of diagrams, we will explain the concept of the celestial sphere, and try to show that the stars with are not visible may be observed in southern hemisphere. Then we will show photographs of some of the constellations which are visible in the southern hemisphere

Motion of the Stars as viewed from Japan

Take pictures of the night sky from a location in Japan looking in several different directions.

Northern Sky	Eastern Sky	Western Sky	Southern Sky

Which Direction is the Observer Facing?

From a photo of the night sky below, is it possible to tell the direction!?

North? South?! East?? West???
In fact, the answer will be different depending on the location where the photograph was taken.

Understanding the Celestial Sphere

Let us imagine that the Earth is surrounded by a large sphere, as shown in the diagram above. In this diagram the stars, which are in reality a range of distances from the Earth, are attached to the surface of this sphere. In this way, an imaginary starry ceiling was devised to represent then night sky, known as the 'celestial sphere'.

Because the Earth as shown above, rotates with the direction of the Polaris as an axis, the star with respect to the celestial sphere is visible as in the figure, as with respect to the celestial sphere been moving to the direction of opposite to the direction of rotation of the earth.
When you are observing the sky from a location the Earth's northern hemisphere, how will it appear?
The Earth is obviously very small compared with the size of the heavens, so it is better to represent our planet with a smaller sphere, as shown in the figure below.

The observer will have part of the celestial sphere obscured by the Earth, so we place him on a flat surface covering the middle of the celestial sphere's interior, as shown below.

　To best represent the observer's appearance of the sky, we will need to make the 'ground' horizontal, and rotate the celestial sphere in an anticlockwise direction, as shown below.
　Since Polaris is in a northerly direction as viewed by the observer, we can then locate south, east and west in the diagram.

Stars not visible in the Northern Hemisphere

　The figure below uses the celestial sphere to show the starry sky as viewed by a northern hemisphere observer (represented by the red person).
There is a problem here! Some of the stars on the celestial sphere are not visible to our observer. Which ones are they?

The invisible stars are below the observer- these are shown in red below.

　As you can see from the above figure, the red stars will be never above the ground. Our observer will never be able to see these stars.
Things to Think About
　Move the observer's location on the surface of the Earth to determine from which location the red stars will be visible.
Where do you have to move the observer to?

Southern Hemisphere Constellations

　Let us move the red person to the southern hemisphere.
This will mean the Celestial Sphere appears as shown below. Now the stars which were not observable from the northern hemisphere (shown in red) are visible.

Motion of the Stars in the Southern Hemisphere

　From the figure above, we can see that from the southern hemisphere, time exposure images of the stars from each direction will be as follows.

North	East	West	South

Further Discussion

Further Discussion

　If we take images in each compass direction from the North Pole, what will they look like? Similarly, think about how the stars will appear as viewed from the Equator.

The Celestial Sphere viewed from the North Pole	The Celestial Sphere viewed from the Equator

　The Celestial Sphere as viewed from the North Pole and the Equator is shown above.
　Hence, we can find the visibility of the stars from each direction in these places.

Motion of Stars from North Pole

Zenith	Horizon

Motion of Stars from Equator

North	East	West	South

Daily Motion of Stars in the Southern Hemisphere

　When you get the opportunity, try to identify and observe some southern hemisphere constellations.

Stars in the Southern Cross	Canopus