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Exhibition Guide

Our Galaxy and the Milky Way

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Purpose of Exhibition

Our Solar System is part of a huge crowd of stars which is called \"the Galaxy\". In the Galaxy, there are two hundred billion stars and interstellar gas distributed like a flattened disk. Since the Sun is located near the external side of the rotation disk, we won't see so many stars by looking into the vertical direction to the disk. However, when we look into the direction of the Galaxy's disk, we see many stars piled up and see them as a faint light belt which is called the Milky Way.
In this exhibition, the Galaxy and the Milky Way is displayed in a big acryl block. The stereoscopic shape of the galaxy is made by putting air bubbles into the big acryl mass. The acryl block is also cut at the point of the Sun vertically to the disk, so that the surface of cross-section as well as the external surface can be observed, in order to show the relation between the Galaxy and the Milky Way.

Additional Knowledge

[Appearance of the Galaxy]\\
Although we can see the whole picture of other galaxies, it is quite difficult to observe our own Galaxy, since we are actually in the Galaxy. This difficulity could be likened to finding yourself in a world without mirrors. (There is no mirror to reflect the Galaxy in space). It is impossible to see your own face without a mirror, since you cannot see yourself from a distance. You have to imagine it by, like touching parts of your body, or looking at other people\&\#39;s faces (supposing that there are no big difference between our body parts since we are all humans). You may guess that your nose sticks up a little more than others or that your eyes are a bit smaller than others. This can also be applied to the Galaxy. Until we are able to travel outside of the Galaxy in the future, we have no choice but to imagine its appearance by observing the motion and distribution of stars and comparing it with images of other galaxies.
The Galaxy is made of a bulge where stars come together, a disk where gas and stars spread in a flattened disk, and a halo which surrounds the edge of the disk spherically (Figure 1). In case of our Galaxy, the bulge, packed with stars in the center, is not spherical but stick-like, therefore our Galaxy is considered to be \"barred spiral galaxy\", which has two arms stretched from both sides of the bulge.
A spiral pattern "spiral arm" can also be seen in the disk. The diameter this disk is about a hundred thousand light years, and our Solar System is located 2.8 million light years away from the center of the Galaxy. 150 globular clusters have been observed in the halo. It is said that there is a huge blackhole in the center of the Galaxy.
The Galaxy is rotating in a disk, and the velocity around the solar system is about 220 kilometers per second. This means that to make a complete rotation on its axis, it takes 240 million years, which seems like forever. However, when you consider the age of the solar system, we have already rotated around the center of the Galaxy about 20 times.


【 References 】

Article by Astronomy Section


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