What is in the universe?

Among the celestial bodies in the solar system, the surface temperature of Mercury and Venus is about 700K, and the temperature of distant Pluto towards the sun is only 50 K at the highest. The surface of Venus is covered with dense carbon dioxide atmosphere and sulfuric acid cloud, and the atmospheric pressure is about 50 atmospheres, while the surface atmosphere of Mercury and Mars is extremely thin, and the atmospheric pressure of Mercury is even less than 2× 10-9 mbar. Earth-like planets (Mercury, Venus and Mars) all have a solid surface, while wood-like planets are fluid planets. The average density of Saturn is 0.70g/cm3, which is smaller than that of water. The average density of Jupiter, Uranus and Neptune is slightly higher than that of water, while the density of Mercury, Venus and Earth is more than five times that of water. Most planets rotate in the forward direction, while Venus rotates in the reverse direction. The surface of the earth is full of vitality, while other planets are an empty and desolate world.

The sun is a common and typical star in the star world. It is found that some red giant stars are thousands of times the diameter of the sun. Neutron stars are only tens of thousands of times the diameter of the sun; The luminosity of Supergiant star is as high as several million times that of the sun, while the luminosity of white dwarfs is less than several hundred thousand times that of the sun. The density of red Supergiant star is as small as one millionth of that of water, while the density of white dwarfs and neutron stars can be as high as10000000 times and10000000000 times of that of water, respectively. The surface temperature of the sun is about 6000K, that of the O star is 30000K, and that of the infrared star is only about 600 K. The average magnetic field strength of the sun is 1× 10-4 Tesla, and the magnetic fields of some magnetic white dwarfs are usually thousands or tens of thousands of gauss (1 gauss = 10-). Some stars are basically constant in luminosity, while others are constantly changing, which is called variable stars. Some variable stars have periodic photometric changes, ranging from 1 hour to hundreds of days. The luminosity of some variable stars changes suddenly, among which the most drastic changes are nova and supernova, and their luminosity can be increased by tens of thousands or even hundreds of millions of times in a few days.

Stars tend to cluster into binary stars or clusters, which may account for 1/3 of the total number of stars. There are dozens, hundreds or even hundreds of thousands of star clusters. Cosmic matter not only forms stars and planets in dense form, but also forms interstellar matter in dispersed form. Interstellar matter includes interstellar gas and dust, with an average of only one atom per cubic centimeter, forming nebulae of various shapes in highly dense places. In addition to the stars and nebulae that emit visible light, there are also ultraviolet objects, infrared objects, X-ray sources, gamma-ray sources and radio sources in the universe.

Galaxies can be divided into elliptical galaxies, spiral galaxies, rod-shaped spiral galaxies, lens galaxies and irregular galaxies. In the 1960s, many extragalactic objects were discovered, which are experiencing explosions or throwing out huge amounts of matter, and they are collectively called active galaxies, including various radio galaxies, Seifert galaxies, N-type galaxies, Makarian galaxies, BL-type celestial bodies in Boetes, quasars and so on. Many galactic nuclei have large-scale activities: airflow with a speed of several Qian Qian meters per second, energy output with a total energy of 65,438+0,055 Joules, mass and particle ejection, intense light changes and so on. There are various extreme physical states in the universe: ultra-high temperature, ultra-high pressure, ultra-high density, ultra-vacuum, ultra-high magnetic field, ultra-high speed motion, ultra-high speed rotation, ultra-large-scale space-time, superfluidity, superconductivity and so on. It provides an ideal experimental environment for us to understand the objective material world.