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Night Sky

The sky has stars, we don’t see stars in the daytime. because the strong light of the sun obscures all the faint light of the stars when looking up at the night sky If the sky is clear, there are no clouds will see many stars twinkling in the sky far away. So we know that in the sky there are the sun, the moon and countless stars.

The world is not a flat land covered by the sky Like all stars, the earth is a spherical object in the sky. When we are on earth, the sky is the territory around the world. infinite beyond The stars we see twinkle those very far away similar to sedentary on the celestial sphere where we see different stars or constellations according to the season of the year because our world is not still but moving in an almost circular motion around the sun but we are on earth so I feel the opposite is to feel like the celestial sphere revolves around the world and can spin one round at the end of a year as well.

The world we live in, the sun, the moon, and the stars are all spherical objects floating in the sky together. Some of them have their own light or not. Some of the stars that we see twinkling in the night sky are the same stars as the sun that has its own light. But it is very far from the world, so we see that it is small. And the starlight that reaches us is not strong enough for us to see those stars in the daytime because the sun is completely covered so saw those stars but at night.

We study astronomy mostly by observing the sky. The night sky is very important. The sky is not a hemispherical object that encompasses the flat earth’s surface, nor is it a spherical body that envelops the earth. with various stars attached to the spherical surface when we are on earth The sky is the territory around the world. Infinitely far away, all the stars and celestial bodies that were visible to the naked eye. agree with a magnifying glass and that are still invisible are all in the sky far from us in different distances.

The stars we see flashing light far away stationary in the sky, but where we see stars or constellations vary according to the seasons of the year It’s not because those stars move. or because the sky moves but because the world We revolve around ourselves every day. and moving around the sun all the time by moving in an almost circular oval and complete one cycle in approximately 365 days. The Earth’s circular motion in the sky We on Earth feel the opposite. The same way we sit on a fast moving train We felt that the fields beside the road It is the party that moves against us. and moving very fast, less than the speed of the train.

So we feel as if the sky around the earth is spherical. which has the sun stuck and which revolves around the earth every day. In addition, the sun also appears It was like moving slowly in the sky. by completing one round in approximately 365 days as well. In the study of astronomy, We determine the position of the stars in the sky by assuming the celestial sphere is the main demarcation.

The celestial sphere is an imaginary sphere. Parallel to the Earth’s sphere, the celestial equator is parallel and in the same plane as the Earth’s equator. If you try to expand the line Earth’s equator, which circles out will overlap the celestial equator in straight line. Through the North Pole and South Pole, which is called the Earth’s axis, it passes through the sphere. The sky at the North Pole and the South Pole and is also called the axis of the celestial sphere.

Telling the location of objects in the sky Use the same method for positioning. objects on earth using the aforementioned celestial sphere which will be discussed how in detail in the next section.

Those in the countryside surrounded by flat fields or by the sea or in any place where a wide sheet of sky may be seen, not blocked by buildings or a large bush often have the opportunity to see the condition of the sky when It’s always late at night at that moment If we take long enough to watch the changes in the sky which proceeds quickly but quiet will be very impressed by miraculous and the beauty of nature like that.

Let’s say we choose to watch the sky at one twilight. of the season when the sky is clear and cloudless when the sun had just set off the distant trees on the western horizon now the sky quickly darkened The moon appeared in a thin crescent. with convex arc Facing west, near the moon, a star appeared brightly and softly. This star is the city star or Venus, the other stars are not visible in the sky. which is not completely dark.

We may record the movement of the stars in the sky. To study and diagnose without much difficulty, by using a normal camera to take pictures of the sky. Photographic film used in general photography today. Sensitive enough to record starlight The method in a nutshell is to set the camera. on a solid base Expose the camera to starlight It takes a long time, for example, 10 minutes or more. moving in the sky will appear as a bright line on the resulting image. When we test the camera like this Photographing the western sky When the sky is dark enough, it will be found that the bright lines of the stars appearing as parallel lines descending into the western horizon.

When shooting some northern skies By the same method, we will find that the stars in the sky in that direction Shows the motion different from the stars in the western sky. Suppose we take a picture with the camera open for about 30 minutes, we will get an image in which each star appears as a bright line. arc of circle which has a common center.

This common center is near a relatively bright star. From the images we can conclude that stars in the north sky appear to move in a circle around a fixed point people near Bangkok You will see stars near this fixed point. It is approximately 14° above the horizon and appears to be fixed in the sky, not moving and almost exactly north. can be used as the main point of direction Once you are familiar with the sky and remember it well This star is commonly known as the North Star (polestar or Polaris).

If we go up north And keep an eye on this star, you will find This star is so high rising from the horizon in Phrae The North Star is approximately 18° above the northern horizon. This star will also appear lower. until when we reach the equator of the Earth, such as Singapore Island This star will land right on the horizon. and cannot be seen easily.

If in doubt The short length of the bright curve shows the motion of the stars in the image. How are they related to each other? And how is it related to the time when the camera is turned on? We may be able to perform a simple analysis to answer this problem.

By determining the common centers of these arcs to be certain. and draw a straight line from the two ends of each curve. to this common center For this we may select only certain arc lines with different distances from the centers. Next, we measure the angles between the radii that are paired at the ends of the curves, as shown in the bottom right image. We will find that each angle All angles are equal. which is why the curve that is away from the center is longer The curve near the center.

The results of this analysis This made it possible to conclude that the sky in the north appear to the observer large sphere revolving around The axis of rotation of this sphere is a straight line passing through the observer. to a fixed point in the sky near the North Star Every star we see is like a bright spot attached to the inner surface of this sphere.

If we were to take several such images of the northern sky in an experiment with different lengths of time for light to enter the lens in front of the camera. Then take the pictures that have been considered side by side, it will be found that the angle at the curve of the star’s brightness act at that common center There is a value that is directly proportional to time. used to open the camera, for example, if we open the camera for 15, 30, 60 and 120 minutes respectively, the resulting angle will be 3° 75, 7° 5; 15° and 30°, respectively, mean that the sky revolves around The axis passes the observer at a constant rate of 15° per hour, so in 24 hours or a day, the sky appears to have rotated one complete cycle, or 360°.

When we conducted some surveys of the movement of stars in the eastern sky. By the same method, similar results are obtained in the western sky. The stars appear to move in parallel lines. However, in this case, the motion of the stars will be moving up from the eastern horizon. For the southern sky We get a similar result to the northern sky. But when we analyze the images we have seen, we find that in this case.

The common center of the circle is below the horizon level, indicating that the sphere’s axis of rotation passes through the observer. and the point which is opposite to the central point in the northern sky when we bring fruit from the southern sky Let’s consider together with the picture of the northern sky. It can be concluded that The entire sky appeared in a large sphere. Centered on this large circular observer, revolving around its axis, it passes through this observer.