1. Stars: The distribution of stars in the universe is uneven. From the day they were born, they gathered in groups and reflected each other to form binary stars, clusters and galaxies ... Stars are burning planets. Generally speaking, the volume and mass of stars are relatively large. It is only because it is too far away from the earth that the starlight appears so weak.
Neutron stars: Neutron stars evolved from stars. Regarding the formation of neutron stars, many people think that some stars in the later stage of evolution had extremely violent nuclear explosions and then contracted sharply. Great pressure is generated inside the star, which squeezes the electrons from the outer layer of the atom into the nucleus, and the protons in the nucleus combine with the electrons to form an extremely tight neutron structure substance. At this time, this star evolved into a neutron star.
Variable stars: In astronomy, those stars whose brightness changes frequently are called variable stars. More often, the light change of a variable star is due to internal reasons, which is called internal variable star. Internal variable stars can be divided into pulsating variable stars, nova and supernova according to the light variable properties.
Binary star: Two stars are very close together, and they move in circular orbits around the same center of mass, so it is difficult for us to distinguish them.
Red giant: If the mass of the star is large enough, the temperature of the center of helium nucleus may reach 1 100 million degrees during the above process. At this time, its core will ignite three helium nuclei to fuse into 1 carbon atom, releasing more energy than hydrogen fusion. At this time, the star releases more energy because of two nuclear reactions at the same time. The soaring energy makes the radiation pressure inside the star greater than the gravitational systolic pressure, which causes the star to expand more violently and turn into a bigger red giant or red Supergiant star. The sun will become a red giant in about 4-5 billion years.
White dwarf: A white dwarf is a star with low luminosity, high density and high temperature. Because of its white color and small size, it is named white dwarf. Some features: (1) is small in size, and its radius is close to that of the planet, with an average of less than 103km. (2) The brightness (the total energy radiated by a star per second, that is, the luminous power of a star) is very small, which is 103 times darker than that of a normal star on average. (3) The mass is less than 1.44 solar masses. (4) The density is as high as 106 ~ 107 g/cm3, and its surface gravity acceleration is approximately equal to 10 times ~ 104 times of the earth. If a man can reach the surface of a white dwarf, he can't stand up, because the gravity on it is too great, and his bones have long been crushed by his own weight. (5) The surface temperature of white dwarfs is very high, with an average of 103℃. (6) The magnetic field of white dwarfs is as high as 105 ~ 107.
Nova: An explosive variable star, also called "guest star". Nova was first observed in the visible light band, and its brightness increased greatly in a short time. The maximum brightness can be increased by tens of thousands to millions of times, which is a small-scale explosion phenomenon produced in the later stage of star evolution.
Supernova: More variable stars than nova explosions. The luminosity amplitude exceeds 17 galaxy, that is, the brightness increases by tens of millions to hundreds of millions of times. This is the most violent explosion phenomenon known in the star world. As a result of the explosion, the star material completely dispersed and became the remnant of the nebula, ending the evolution history of the star; Or most of the mass is ejected, leaving some materials to collapse into white dwarfs, neutron stars or black holes, thus entering the late and final stage of star evolution. After supernova explosion, intense radio source, X-ray source and cosmic ray source are formed. Supernovae are also major contributors to interstellar heavy elements.
2. Planets: Planets are celestial bodies that do not emit light by themselves and surround the stars. Generally speaking, a planet needs to have a certain mass, and the mass of the planet should be large enough to make its shape about spherical. Those with insufficient mass are called asteroids.
3. Satellite: A planet refers to a celestial body that does not emit light. A satellite is a celestial body that moves in circles around a star. The moon itself is a planet, but because it is influenced by the gravity of the earth, it turns around the earth, so it becomes the satellite of the earth. Accurately speaking, the criteria for dividing satellites and planets are not the same. Satellites are divided according to the relationship between celestial bodies, and planets are divided according to the nature of celestial bodies, so the moon has its own properties.
Comet: Comet consists of frozen impurities and dust. Astronomers vividly call it a "dirty snowball". When it runs near the sun, under the action of sunlight and heat, the dirty snow, solidified gas and ice on the outer layer of the "dirty snowball" quickly evaporate, gasify, expand and erupt. At this time, the volume of the comet expanded rapidly and was obviously divided into two parts: the head and the tail of the comet. The brightest part in the center of the comet's head is the nucleus, which is the main body of the "dirty snowball"; The substance vaporized and erupted on the surface of the nucleus is wrapped around the nucleus, forming a coma. The coma is also covered with a thin layer of hydrogen cloud, called comet cloud. The tail dragging behind the coma head is the coma tail, which is formed because the gas, dust and other substances in the coma head are pushed out by the strong radiation pressure of the sun and the solar wind. So the tail always turns its back on the sun, and the closer it is to the sun, the longer it is.
5. Meteors and meteorites: In addition to planets, satellites and comets, there are countless small celestial bodies and dust in interstellar space, which are collectively called meteor matter, or meteoroids and micrometeoroids (dust) respectively. As the earth moves in space, it will meet a large number of meteors every moment. Among them, meteoroids over millimeters enter the atmosphere and glow at a height of 80- 120 km due to atmospheric friction, thus drawing a light trace in the starry sky and quickly disappearing. This phenomenon is called a meteor.
Meteorites generally burn and vaporize in the atmosphere, and only larger meteoroids or micrometeoroids can fall or fall to the ground, becoming meteorites and micrometeoroids respectively.
Ps: The above is personal classification. I wonder if it's wrong. For the whole vast universe, human's current scientific understanding is limited. Only by gradually discovering and constantly changing the original astronomical knowledge can we explain the whole universe more deeply.
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Answer: quality inspection 945 1
Level: advanced
September 2006 19 1, star (self-luminous)
2. Planets (reflected light)
There are roughly two kinds.
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Answer: 88900
Level: novice
September 2006. star
2. Planets
3. Satellite
4. Comets
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Answer: fmy 189 1
Grade: God
September 20, 2006 can only be divided into stars, planets (including asteroids and dwarf planets), satellites and comets. If a "meteor" is also a star, it is some meteorites that are seen only after entering the atmosphere and rubbing against it.
However, some people have put forward the idea of changing the name in the future: there are too many categories of "planets" at present, which are easy to be confused. Asteroids may be called "wandering stars" and dwarf planets may be called "dwarfs".
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Answer: Sui Feng
Level: advanced
On September 20, 2006, a star composed of hydrogen and helium (self-luminous, bright) planets could not carry out thermonuclear reaction. Earthlike planets are rocks, containing more oxygen, silicon and aluminum. Wooden planets have more liquid components, mainly liquid hydrogen (according to scientists in the former Soviet Union, Jupiter can replace the sun after its demise, because it may also be undergoing thermonuclear reactions inside) () dark) and the planets we see are flickering, which is obviously different from stars (they don't flicker). There are other satellites. Our earth is the moon, and satellites of other planets can only be seen through telescopes. Comets made up of dust and ice crystals have a long tail (which appears periodically). For example, Comet Halley approaches the Earth once every 276 years. Finally, a meteor, a very small planet. The meteors we see may fall to the ground and be consumed after a long journey.