Shulou(Shulou.com)11/24 Report--

The Milky way is our galaxy, which contains hundreds of millions of stars, planets, moons, interstellar gas and dust. Our sun and earth are part of the Milky way, but where exactly are we in the Milky way? To answer this question, we need to explore the Milky way from within the Milky way, understand its shape and structure, and how it formed and evolved.

Explore the Milky way from the inside of the Milky way if we stand on the earth and look up into the night sky, we can see a bright band extending from one side to the other. This is what we see as part of the Milky way, the Galaxy in which we are located. The galaxy is actually made up of countless stars that look like clouds because they are so far away. These stars revolve around the center of the Milky way, forming a flat disk-like structure. We can think of the Milky way as a huge spinning record, and we are on one of the scratches.

Early Milky way Theory the human understanding of the Milky way was not very clear from the very beginning. In ancient times, people thought that the silver path was a trace left by gods or heroes, or rivers or milk in the sky. Until the end of the 17th century, the Italian astronomer Galileo looked at the galaxy with a telescope and found that it was actually made up of countless stars. He speculates that these stars may form a huge cluster, and the sun and the earth are one of them.

Galileo Galilei's observation of the Milky way in globular clusters and spiral nebulae opened a new era, but he did not fully reveal the truth about the Milky way. In the 18th and 19th centuries, astronomers discovered more celestial phenomena, such as globular clusters and spiral nebulae. Globular clusters are spherical structures formed by dense clusters of hundreds of thousands to millions of stars, usually distributed outside the disk of the Milky way. Spiral nebulae are spiral structures made up of gas, dust and stars that look like miniature galaxies.

At that time, there were two mainstream theories to explain these phenomena. One is the island universe theory, which believes that the spiral nebula is a separate galaxy far away from us, and our Milky way is just one of them. The other is the spiral fog theory, which holds that the spiral nebula is the internal structure of our own Milky way, and our Milky way is the only galaxy in the universe.

What is the shape of the Milky way? to determine the shape of our Milky way, we need to know its size and boundaries. However, this is not an easy task, because we observe it from within the Milky way, like an ant walking back and forth on a large plate, it is difficult to see the whole plate. We need to find some celestial bodies that can be used as references to help us measure the size and direction of the Milky way.

Fortunately, we have some references, that is, globular clusters. Globular clusters are the oldest group of stars in the Milky way. they were formed at the beginning of the birth of the Milky way, about 13 billion years ago. They are distributed outside the disk of the Milky way, forming a spherical halo layer that surrounds the center of the Milky way. Because the distance of globular clusters is relatively stable, we can use them to determine our position and orientation relative to the center of the Milky way.

To measure the distance of globular clusters into radio telescopes, we need to use a special kind of telescope, that is, radio telescopes. Radio telescopes are not used to observe visible light, but to receive radio waves emitted from the sky. Radio waves are electromagnetic waves whose wavelengths are much longer than visible light, so they can penetrate gas and dust inside the Milky way without being obscured or scattered. This allows us to see more distant and clearer celestial bodies.

The radio telescope was first invented by Karl Jensky, an American physicist, in the 1930s. Using a simple antenna receiver, he found a strong radio source in the center of the Milky way. Later, people continued to explore the Milky way and other galaxies with larger and more sophisticated radio telescopes, and found many wonderful phenomena, such as pulsars, quart stars, radio nebulae and so on.

Doppler effect to use radio telescopes to measure the distance of globular clusters, we need to use an important physical principle, that is, the Doppler effect. The Doppler effect means that when a wave source moves relative to an observer, the wavelength received by the observer will change. If the wave source and the observer are close to each other, the wavelength received by the observer will be shorter; if the wave source and the observer are far away from each other, the wavelength received by the observer will be longer.

The Doppler effect is applicable not only to sound waves, but also to light and radio waves. When a celestial body moves towards us, its light or radio waves move to blue; when a celestial body moves away from us, its light or radio waves move to red. This change in color is called redshift or blue shift. By measuring the redshift or blue shift of light or radio waves emitted by a celestial body, we can know its speed relative to us.

With radio telescopes and Doppler effects in the structure of the Milky way, we can measure the distance and velocity of globular clusters to determine our position and orientation relative to the center of the Milky way. By observing hundreds of globular clusters, we can make a startling discovery: we are not at the center of the Milky way, but about 26,000 light-years from the center. Moreover, our galaxy is not a uniform disk-shaped structure, but a spiral structure with two obvious arm-shaped branches. This is what our Milky way really looks like.

Our Milky way is a typical spiral galaxy, which consists of four main parts: core, disk, arm and halo. The core is the central region of the Milky way, which contains a huge black hole and some aging stars. The disk is the most obvious part of the Milky way. it is a flat circular structure that contains a large number of young stars, gas and dust. Arms are spiral branches that extend from the disk. They are the main sites for star formation and the brightest parts of the Milky way. Halo is the outermost part of the Milky way. it is a spherical structure that contains some ancient stars and globular clusters.

How many stars are there in the Milky way? we already know what our Milky way is like, so how many stars are there in it? This question is not easy to answer because we cannot count all the stars and can only use some statistical methods to estimate. A common method is based on the mass of the Milky way and the average stellar mass. Based on the observed data, we can estimate that there are about 3.3 × 10 ^ 11 stars in the Milky way.

Of course, this figure is only a rough estimate, in fact, there may be a lot of error. Because there are many other components in the Milky way, such as black holes, neutron stars, planets, gas, dust and so on, they all affect the mass and density of the Milky way. Moreover, different types and ages of stars will have different mass and brightness, which will also affect our judgment of the number of stars. Therefore, in order to get a more accurate answer, we also need more and more accurate observation data and more complex and more elaborate calculation methods.

This article comes from the official account of Wechat: Vientiane experience (ID:UR4351), author: Eugene Wang

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