Category

Visibility of the Stars 2

Introduction

Here we will show that changing the observing latitude alters both the appearance of constellations, and the constellations which can be seen

　To understand how the appearance of the night sky changes with latitude, we need to move on from the concept of observing the celestial sphere from the Earth's surface, and instead imagine looking down on an observer standing on the surface of the Earth from a point in space.
However, understanding the concept will be the most difficult part of this experiment. With the aid of a model, and by acquiring images of the night sky, it will be possible to appreciate the way its appearance changes with location.
　Here we make a drawing of Orion and use a projector to produce an image of it on the ceiling of the classroom. Pupils in different locations in the room will see it in different ways.
We can imagine the whole classroom to be the Earth, with the front half being the northern hemisphere, the rear half being the southern hemisphere, and the whole ceiling being the celestial sphere. When pupils look at the projected image of Orion on the ceiling, those at the rear of the class will see it upside down.
　Hence, this experiment illustrates the different views of the stars obtained from the northern and southern hemispheres.

Experimental Method

Is the appearance of constellations the same from different locations?

　Are the same stars visible in Japan and Australia?
　As seen from Japan, stars which are visible in the southern part of the sky will also be visible in Australia.
(e.g. Scorpius in summer, and Orion in winter)

　So, when Orion is observed from Australia, how will it appear?
　Will it look the same as it does from Japan?

Things to Prepare

　Computer; Figure of Orion; Projector; Photo of Orion as observed from Japan; World map or globe

Experimental Procedure

1. Acquire a photo of Orion as seen from Japan
   
2. Using the classroom to represent the Earth, divide it up so that the front half is the northern hemisphere side and the rear half is the southern hemisphere side.
   As the classroom represents the Earth, so the ceiling will be the sky.
   
3. The Orion figure is projected onto the ceiling of the classroom with the projector. First, let us think about how the Orion figure appears from the front, i.e. northern hemisphere, side of the classroom, in order to appreciate the way in which Orion appears from Japan. Pupils near the front should try sketching the way the projected figure of Orion appears to them.
   
4. Next, we will consider the way in which the projected figure of Orion appears from the rear, or southern hemisphere, side of the classroom. Now pupils at the back should sketch the way in which they observe the Orion figure

Japan is in the northern hemisphere, while Australia is in the southern hemisphere.	Using the classroom to represent the earth, the front half is the northern hemisphere and the rear half is the southern hemisphere.

Experimental Results

Upside-Down Orion

　From the front of the classroom (on the northern hemisphere side, representing the view from Japan) the projected view of Orion looked the same as the way Orion usually appears, but from the back of the classroom (on the southern hemisphere side, representing the view from Australia) the projected view of Orion was upside-down compared with with way it is normally seen.

Photos & Figures

Diagram of Orion	Detailed figure of Orion (click for larger view)	Photo of Orion Taken on 2002 Dec 17 from the roof of MUE using a cooled CCD camera. Click on image for larger version. (Credit: Kazutaka Yoshida)