How does the Hubble telescope work?

Galileo's telescope

People are always curious about things they don't know, such as what distant celestial bodies look like. Therefore, people fantasize that there is a kind of clairvoyance that can see things in the distance. 1608, clairvoyance was finally invented, and this is the telescope.

This year, an apprentice played in a glasses workshop in Holland. When he observed the object with two lenses, he found that the distant object was very close to him. Inspired by this, he invented the telescope. His boss lost no time in turning this invention into a commodity and dedicated it to the government. With the help of these telescopes, the weak Dutch navy defeated the powerful Spanish fleet and made the Netherlands independent.

The Dutch blocked the invention very tightly, but the news about the telescope made Galileo know, and he immediately realized the value and function of this kind of thing. After careful study, Galileo also independently invented his own telescope. When this astronomical telescope slowly swept across the sky, the curtain of modern science slowly opened and the most basic facts about astronomy were discovered one by one. People say; "Columbus discovered the new continent and Galileo discovered the new universe."

Galileo's telescope is very simple. It consists of two lenses. The one in front is called the objective lens, which is a lens with a thin edge and a thick middle. With amplification function. The back is called eyepiece, and the middle of the lens is thin and the periphery is thick, which has the function of reducing. In this way, two lenses combined with a cylinder is the simplest telescope. Galileo used it to find that there are always four small stars around Jupiter, which are four satellites of Jupiter, also called Galileo satellites; He also found that Saturn seems to have a pair of big ears, which are Saturn's rings; He also carefully observed the craters of the moon. Thanks to the telescope, people finally know that the Milky Way in the sky was originally composed of countless stars. These new discoveries became strong evidence for Copernicus and Heliocentrism.

Kepler telescope

Kepler further developed the telescope, changing the eyepiece of the telescope from concave lens to convex lens, so that both the front and rear lenses have magnifying effect and the magnification of the telescope is improved. It looks like an inverted telescope, but it has little effect on astronomical observation. This kind of telescope is called Kepler telescope.

If the convex lens is facing the sun, it will have a very bright focus on the ground. The distance from this focal point to the center of the lens is called the focal length of the lens. For Kepler telescope, the magnification can be obtained by dividing the focal length of the objective lens by the focal length of the eyepiece. The lens barrel of Kepler telescope is usually very long, which also improves its magnification.

It was William Herschel who made the Kepler telescope develop greatly, that is, the man who discovered Uranus. He grinds the lenses of many large telescopes in his life. His telescope looks like a giant gun pointing to the sky. This makes his observation method always superior to others, and also brings him many academic achievements. Under his leadership, his sister and son also became astronomers.

Newton telescope

Galileo's and Kepler's telescopes are both refractive telescopes, which are composed of two lenses. Their working principle is not complicated, but their shortcomings are obvious. The magnification of galileo telescope is too small, while the lens barrel of Kepler telescope is too long. Is there any way to make a telescope with a large magnification tube and not long? Reflective telescopes have this advantage.

Reflective telescopes are subdivided and there are many kinds, the most common one is Newton's reflective telescope. It was invented by British physicist Newton in 167 1 year. Its objective lens is a concave mirror, not a convex lens, and it is installed behind the telescope tube, not in front. Its surface is plated with silver, which can concentrate the light to the front. A mirror is fixed in focus. This mirror rotates the image of the objective lens by 90 degrees and shines on the wall of the telescope. On the wall of the telescope, there is an eyepiece. Strictly speaking, it is an eyepiece group, which consists of several lenses, equivalent to an eyepiece, which can improve the imaging quality. When observing celestial bodies with this telescope, the observer is not behind the telescope, but on the side of the telescope. Because its reflector is very complicated to fix, its lens barrel is not a standard circle, but there is a bulge in the middle, just like a gourd, so it is also called a treasure gourd telescope.

The development of telescope

The above is the basic overview of three relatively simple telescopes, which is too simple for more professional astronomical observation. Far from meeting the needs of observation. Later, seglin telescope, Schmidt telescope and Maksutov telescope were invented, all of which were named after the inventors, and their optical path principles were complicated.

People often pursue the telescopic magnification of a telescope, and it is impossible to expand it indefinitely. Too high magnification will affect its imaging quality. For astronomical telescopes, magnification is a secondary aspect. What people pursue is the diameter of the objective lens. The larger the diameter, the more photons it collects and the stronger the resolution.

1948, the United States made an astronomical telescope with a diameter of 5 meters, which was located at Paloma Mountain Observatory. It greatly broadened the horizons of astronomers, helped them to take many photos of the deep space of the universe, and suddenly improved the research level of American astronomers. Unwilling to lag behind, the Soviets couldn't sit still, so they built a telescope with a diameter of 6 meters, but the imaging quality of this telescope with the largest aperture in the world at that time was very poor.

Now people have realized that the diameter of the telescope cannot be made too large. If the diameter is too large, the weight of the lens will be too large, which will lead to the deformation of the lens, and the weight of the lens will also press the electrical equipment carrying it to operate abnormally. The new idea to continue to improve the resolution of the telescope is to make many small lenses and then combine them into a large lens.

On the earth, the dust in the air and the constantly shaking atmosphere have become important factors affecting the observation quality of telescopes. Nowadays, astronomical telescopes are all built on sunny and rainy mountains. But this is still not ideal, so people put telescopes into space. Hubble telescope is the best space telescope at present. It orbits the earth like a satellite and provides us with many high-precision photos of celestial bodies. It is called the "discovery machine" of astronomy.

Telescope parts

The star moves from east to west bit by bit in the sky. When you aim at it with a telescope, you will soon find it moving, so you need an automatic tracking device. Now even telescopes used by astronomy enthusiasts have automatic tracking devices. In addition, there is a star guide mirror, with its help, it is easy to find the target. If you want to take pictures of what you see, there is also a camera interface. If you want to observe the bright sun, there is also a filter, because observing the sun with a telescope will burn your eyes. Galileo suffered from eye diseases in his later years, which was caused by observing the sun through a telescope.

At present, the eyepiece of a telescope usually consists of several groups of lenses, so that different telescopic magnifications can be obtained. If you want to see a wide field of vision, use a low magnification eyepiece, and if you want to see a fine structure, use a high magnification eyepiece.

In early telescopes, because the lens manufacturing process was simple, aberrations and chromatic aberration often appeared, which distorted the things you saw or the colors. In order to solve this problem, people try to extend the focal length of the telescope. 1722, the telescope for measuring the diameter of Venus without Ladere has a focal length of 65 meters, which is half of the 100-meter sprint orbit. Later, the achromatic telescope was born. Its eyepiece consists of two lenses, a convex lens and a concave lens, which can eliminate many problems such as chromatic aberration and spherical aberration.

From the birth of the telescope to the present, it has undergone several generations of evolution, so many stories have been produced. To be sure, as long as people are curious to explore the mysteries of the universe, the story about telescopes will never end. (National Space Administration Network/Beichen feed)

Background knowledge:

Chromatic aberration: The white light beam emitted from the white object point to the optical system is refracted by optical series, and the red, orange, yellow, green, cyan, blue and violet light that make up the white light beam cannot converge at the same point, that is, the white object point cannot form a white image point, but a color image point, which is called chromatic aberration.

Spherical aberration: a monochromatic cone-shaped beam emitted from an object point on the main shaft to the optical system. After this kind of optical series refraction, if the light beams with different aperture angles of the original beam cannot cross at the same position on the main shaft, thus forming a diffuse spot (commonly known as fuzzy circle) on the ideal image plane on the main shaft, the imaging error of this optical system is called spherical aberration.