All these planets revolve around the sun in elliptical orbits, although it is very close to a circle except Mercury. Planetary orbits are more or less in the same plane (called ecliptic plane, based on the orbital plane of the earth). The ecliptic plane is only 7 degrees from the equator of the sun. Pluto's orbit is mostly outside the ecliptic, with an inclination of 17 degrees. The above picture shows the relative size and relationship of each orbit from a specific perspective higher than the ecliptic plane (non-circular phenomenon is obvious). Their orbits run in the same direction (counterclockwise from the north pole of the sun), so scientists exclude Pluto from the nine planets. Except Venus and Uranus, the rotation direction is the same.
Galaxy (Galaxy)
The Milky Way is the galaxy to which the earth and the sun belong. It is named because the bright band whose main part is projected on the celestial sphere is called the Milky Way in China.
The discovery of the Milky Way has gone through a long process. After the invention of the telescope, Galileo first observed the Milky Way with a telescope and found that the Milky Way was made up of stars. Then there are T. Wright, I. Kant, J. H. Lambert, etc. It is believed that the Milky Way and all the stars may converge and integrate into a huge star system. /kloc-in the late 8th century, F.W. Herschel started the observation of star counting with a self-made reflecting telescope to determine the structure and size of the star system. He asserted that the star system is flat and the sun is not far from the center of the disk. After his death, his son, J.F. Herschel, followed in his father's footsteps, continued his in-depth research and extended the work of counting satellites to Nantian. At the beginning of the 20th century, astronomers called the star system with the Milky Way as its apparent phenomenon the Milky Way. J.C. Kapteyn used statistical parallax method to measure the average distance of stars, and combined with the counting of stars, a model of the Milky Way was obtained. In this model, the sun is at the center, and the Milky Way is disc-shaped, with a diameter of 8,000 parsec and a thickness of 2,000 parsec. H shapley uses the period-luminosity relationship of Cepheid variable to measure the distance of globular clusters, and studies the structure and size of the Milky Way from the distribution of globular clusters. His model is that the Milky Way is a lenticular star system, and the sun is not in the center. Shapley concluded that the Milky Way has a diameter of 80,000 parsec and the sun is 20,000 parsec from the center of the Milky Way. These values are too large, because shapley did not consider interstellar extinction when calculating the distance. In the 1920s, after the discovery of the rotation of the Milky Way, shapley's model of the Milky Way was recognized.
The Milky Way is a huge spiral galaxy, Sb type, with four spiral arms. Contains 100 billion or 200 billion stars. The overall rotation of the Milky Way is not good. The rotation speed at the sun is about 220 km/s, and the sun revolves around the center of the Milky Way for about 250 million years. The absolute visual magnitude of the Milky Way is -20.5. The total mass of the Milky Way is about 1 trillion times that of our sun, and about 10 times that of all the stars in the Milky Way. This is a strong evidence that dark matter exists in our galaxy, far beyond the bright astrolabe. Regarding the age of the Milky Way, the popular view is that the Milky Way was born shortly after the Big Bang. Calculated by this method, the age of our galaxy is about 65.438+0.45 billion years old, and the upper and lower errors are more than 2 billion years each. The scientific community believes that the "big bang" of the birth of the universe occurred around. ...
The Milky Way is the star system where the solar system is located, including120 billion stars, a large number of star clusters and nebulae, and various types of interstellar gas and dust. Its total mass is 654.38+04 billion times that of the sun. Most stars in the Milky Way are concentrated in a oblate sphere, which is shaped like a discus. The protruding part in the middle of the oblate sphere is called the "nuclear sphere" with a radius of about 7000 light years. The center of the core ball is called "silver core" and the periphery is called "silver disk". There is a bigger sphere outside the silver disk, where there are fewer stars and less density. It is called "Silver Halo" with a diameter of 70,000 light years. The Milky Way is a spiral galaxy with a spiral structure, that is, it has a silver center and two spiral arms, which are 4500 light years apart. The rotation speed and period of each part of it are different because the distance from the silver center is different. The sun is about 23,000 light years away from the galactic center, and it orbits the galactic center at a speed of 250 km/s with a period of about 250 million years.
About 90% of galactic matter is concentrated in stars. There are many kinds of stars. Stars can be divided into five star families according to their physical properties, chemical composition, spatial distribution and motion characteristics. The youngest extreme group I stars are mainly distributed on the spiral arms in the silver disk; The oldest extreme group II stars are mainly distributed in silver halos. Stars often gather in clusters. In addition to a large number of binary stars, more than 1000 clusters have been found in the Milky Way. There are also gases and dust in the Milky Way, accounting for about 10% of the total mass of the Milky Way. The distribution of gas and dust is uneven, some gather into nebulae, while others are scattered in interstellar space. Since 1960s, people have discovered a large number of interstellar molecules, such as carbon monoxide and H2O. Molecular clouds are the main places where stars form. The core of the Milky Way, the silver nucleus or silver nucleus, is a very special place. It emits intense radio, infrared, X-ray and gamma-ray radiation. Its nature is not clear, and there may be a giant black hole, and its mass is estimated to be tens of millions of times that of the sun. Little is known about the origin and evolution of the Milky Way.
197 1 year, British astronomers Lyndon Bell and Martin Ness analyzed the infrared observation and other properties of the central region of the Milky Way, pointed out that the energy in the center of the Milky Way should be a black hole, and predicted that if their hypothesis is correct, a small-scale source emitting radio emission should be observed in the center of the Milky Way, and the radiation properties should be similar to those of people. Three years later, such a source was discovered, which is Sagittarius A.
Sagittarius A is very small, only equivalent to the size of an ordinary star. The radio emission intensity of Sagittarius A is 2 *10 (34th power) erg/s, which is located within 0.2 light-years of the dynamic center of the Milky Way. It is surrounded by moving ionized gas with a speed as high as 300 km/s, and there is a strong infrared radiation source. It is known that the activities of all star-level celestial bodies cannot explain the peculiar characteristics of Sagittarius A, so Sagittarius A seems to be the best candidate for massive black holes. However, because there is no conclusive evidence of massive black holes at present, astronomers carefully avoid mentioning massive black holes in conclusive language. Our Milky Way contains about 200 billion stars, including about 1000 billion stars, and the sun is a typical one. The Milky Way is a fairly large spiral galaxy, which has three main components: a silver disk with spiral arms, a silver center protruding from the center and a halo.
star
A spherical or quasi-spherical object composed of hot gas, which can emit light by itself. The nearest star to the earth is the sun. Followed by proxima centauri Centauri, whose light takes 4.22 years to reach the earth. On a clear moonless night, most people can see about 3000 stars with the naked eye somewhere. With the help of a telescope, you can see hundreds of thousands or even millions. It is estimated that there are about 200 billion stars in the Milky Way. The stars are not motionless, just because they are too far away from us, and it is difficult to find their position changes in the sky without special tools and methods. So the ancients regarded them as fixed stars and called them stars.
Protein is the material basis of life. Without protein, there would be no life. Therefore, it is a substance closely related to life and various forms of life activities. Protein participates in every cell and all important parts of the body. Protein accounts for 16.3% of human body weight, that is, an adult weighing 60kg has about 9.8kg of protein in his body. There are many kinds of protein in human body, with different properties and functions, but they are all composed of more than 20 kinds of amino acids in different proportions, which are constantly metabolized and updated in the body. The ingested protein is digested and decomposed into amino acids in the body, which is mainly used to recombine into human protein according to a certain proportion after absorption. At the same time, the new protein is constantly metabolized and always in a dynamic balance. Therefore, the quality and quantity of food protein and the proportion of various amino acids are all related to the amount of protein synthesized by the human body, especially the growth and development of teenagers, the prenatal and postnatal care of pregnant women and the health and longevity of the elderly, which are closely related to the amount of protein in the diet.
nucleic acid
Nucleic acid is an important biomacromolecule, and its building block molecule is nucleotide.
Naturally occurring nucleic acids can be divided into:
Deoxyribonucleic acid
ribonucleic acid
DNA stores all the genetic information of cells, which is the material basis for the continuous evolution and generation reproduction of species.
There are three types of RNA involved in protein synthesis:
Transfer ribonucleic acid
∣ ribosomal RNA
Messenger RNA
Enzyme: biocatalyst, except for a small amount of RNA, almost all of which is protein. Enzymes do not change the equilibrium of the reaction, but accelerate the reaction by reducing the activation energy.