(1) A celestial body shining in the sky at night.
(2) thin and small. Astronomers usually divide the luminous ability of stars into 25 magnitudes, and the difference between the strongest luminous ability and the worst luminous ability is about 1 billion times. The brightness of stars is often expressed by magnitude. The brighter the star, the smaller the magnitude. The magnitude measured on the earth is called apparent magnitude; The magnitude reduced to 1 parsec from the Earth is called absolute magnitude. The magnitude of the same star measured by detecting elements sensitive to different bands is generally unequal. At present, one of the most commonly used magnitude systems is the three-color system of U (ultraviolet), B (blue) and V (yellow) (see photometry system' "class=link> Photometric system); B and v are close to photographic magnitude and visual magnitude respectively. The difference between them is the commonly used color index.
2 Formation Principle Editor
The brightness and darkness of the stars
determine whether people observe the stars as bright or dark. There are two main factors:
First, the luminous ability of the stars;
Second, the distance between the stars and people.
Astronomers usually divide the luminous ability of stars into 25 magnitudes
, and the difference between the strongest luminous ability and the worst luminous ability is about 1 billion times.
The star that is close to people has strong luminous ability, so people will light up when they see it. However, even if a star with a fairly strong luminous ability is far away from people, its brightness may not be as good as a star with tens of thousands of times worse luminous ability.
3 internal structure editing
classification of stars
Stars can be roughly divided into planets, stars, comets, etc.
1 Planets themselves don't emit light, but what we see is the light of the sun reflected by them
2 Stars are large celestial bodies like the sun, which react inside themselves and radiate energy into space in the form of light
3 comets like Halley's comet, and the light we see is that when they pass through the solar system, The phenomenon caused by the comet's tail whose material is melted, so the comets you see often drag their long tails. Most of the stars you can see at night are stars, and a few of them are stars in our solar system, such as Venus, Mercury and Mars. The luminous principle of stars is similar to our solar image. Most of them release energy during the process of hydrogen condensation into helium nuclei, and some of them release energy through helium fusion. It is only because they are far away from us that they look like a gentle little star. In fact, they are much bigger than the sun. The planet looks bright because it reflects the light from the sun, but it only takes up the light near us and looks brighter than the stars.
Understanding the Stars
The sun, which looks as big as the moon in the sky, has a diameter of 1.392 million kilometers and can hold 1.3 million earths. Coincidentally, the diameter of the sun is about 4 times that of the moon, but its distance to the earth is about 4 times longer than that of the moon, so it looks about the same size.
As a satellite, the moon is one of the 66 satellites found in the solar system. There are only four or five satellites larger than the moon, of which Ganymede, the largest in diameter, has a diameter of more than 5,2 kilometers. Most of the others are only tens to hundreds of kilometers.
As a planet, the earth ranks fifth among the nine planets in size, and is considered to be of medium height. The largest Jupiter is 13 times the size of the earth, the brightest Venus is about the same size as the earth, and the red Mars is only one-eighth the size of the earth.
compared with the parents of the solar system-the sun, planets and satellites are really tiny, just like sesame seeds and watermelons. The sun is really exclusive in the solar system. However, compared with the stars that look like the tip of a needle in the sky, the dazzling sun will be eclipsed ―― it is only one of the hundreds of millions of < P > stars, and it can only be regarded as a medium size. Antares in Scorpio is 6 times the diameter of the sun, and Betelgeuse in Orion is 9 times the radius of the sun. There is a star in Cepheus that is bigger, with a radius of 1,6 times that of the sun, reaching 1.1 billion kilometers. If it is placed in the position of the sun, even Jupiter will be in it.
However, most of them are red giants in a late stage of evolution, and their density is extremely small.
Of course, some stars are much smaller than the sun. White dwarfs, which are at the end of stellar evolution, are smaller than the Earth, ranging in diameter from several hundred kilometers to several thousand kilometers. The smallest star, the neutron star, is only 1 kilometers in diameter. Don't underestimate these two kinds of small stars. Although they are small, they are very massive, and they are generally equivalent to the sun. So their density is amazing. The density of neutron stars is 1 million times that of the sun.
4 classification editing
Seniors
Stars are divided into categories: stars, planets, satellites, dwarf planets (this classification is only in the solar system), and small celestial bodies (asteroids, comets, etc.)
Stars are divided into stages: nova, main sequence star, red giant star, supernova (divided into the following categories) -1 white dwarf star, 2 neutron star. 3 black hole
stars are divided into (brownish red) dwarfs, (blue, blue white, yellow, red) giants and (blue, red) Supergiant star
stars are divided into O, B, A, F, G, K, M and additional types of R, N, S
stars according to the spectrum.
The moon is the most obvious example of a natural satellite. In the solar system, all planets except Mercury and Venus have natural satellites. There are at least 16 known natural satellites in the solar system (including the larger fragments that make up the planetary ring). A natural satellite is a planet that orbits a planet, and a planet orbits a star. For example, in the solar system, the sun is a star, and our earth and other planets revolve around the sun, while planets such as the moon, Enceladus and Tianwei revolve around our earth and other planets. These planets are called natural satellites of planets. Jupiter has the largest number of natural satellites, of which 17 have been confirmed, and at least 6 have yet to be confirmed. Natural satellites vary in size and are very different from each other. Some of them are only a few thousand meters in diameter, for example, the two small moons of Mars, and some small satellites around Jupiter, Saturn and Uranus. There are several that are bigger than Mercury, such as Titan, Ganymede and Callisto, all of which are over 5,2 kilometers in diameter.
6 factors for observing stars
First, the luminous capacity of stars;
the second is the distance between the stars and people.
Astronomers usually divide the luminous ability of stars into 25 magnitudes
, and the difference between the strongest luminous ability and the worst luminous ability is about 1 billion times.
7 Representation method of star brightness Edit
The brighter the star [1], the smaller the magnitude. One of the most common magnitude systems is the three-color system of U (ultraviolet), B (blue) and V (yellow) (see photometry system "class = link >; Metering system "), absolute visual magnitude M=+4.83, color index B-V=.63, U-B=.12. The color temperature can be determined by the color index.
The star that is close to people has strong luminous ability, so people will be very bright when they see it. However, even if a star with a fairly strong luminous ability is far away from people, its brightness may not be as good as a star with tens of thousands of times worse luminous ability.
For example, there is a star named "Antares", which is about 22 million times the size of the sun and its luminous capacity is about 5, times that of the sun. But because it is 41 light years away from the earth, people can only see that it is a bright star with red light. If Antares is moved to the position of the sun, the light and heat it emits will bake the earth into a big stone ball where everything disappears.
8 star shape editing
Without external force, all objects tend to gather towards the center under the action of universal gravitation. The most concentrated result is a spherical shape! Although the star is solid on the surface, it is possible to transform it into a sphere because the solid is also deformable and the solid particles are movable.
There are six stars in the summer night.
The energy activities inside the stars make the stars irregular in shape. However, the stones in the mountains roll down from the heights due to the gravity of the stars, and the rivers carry the sediment from the heights to the low-lying oceans (rivers also flow due to the gravity of the stars). These are all examples of concentration towards the center, and they all make the stars change from irregular to spherical. If the star stops moving inside, many hundred million years later, the star will probably become a very standard spherical shape (except centrifugal force and gravity of other celestial bodies).
Many asteroids have small gravity because of their small mass, and the stars are generally made of hard solid rocks, so it is difficult to complete the process of moving to the center under their own gravity, so their shapes are grotesque, oval and rod-shaped.
However, for various reasons, the star is just an ellipsoid close to a sphere.
9 Legends of Stars Editor
When night falls, the stars shine in the sky. These seemingly small stars are actually very different from what we see with the naked eye and have many unknown secrets.
1 Brightest Planets Editor
On the earth, human beings can see five planets with naked eyes, among which Venus is the brightest. Although Venus is far less bright than the sun and the moon, it is 14 times brighter than the famous Sirius (the brightest star in the whole day except the sun), like a dazzling diamond.
Venus
Venus is not only very bright, but also very "individual". It is the only big planet in the solar system that rotates in the opposite direction to other planets, from east to west. Therefore, on Venus, the sun rises in the west and sets in the east.
11 The oldest star editor
Since ancient times, people have used "eternity" as a metaphor for the long time, but eternity is not as long as a star.
36, light years away from the Earth, there is a giant star numbered HE17-524. Its age is about 13.2 billion years, and its formation can be traced back to the early days of the universe (the formation period of the universe is currently recognized as 13.7 billion years). [2]
Stars
12 Fastest Stars Editor
Whenever people look at stars, they are used to looking for them in a fixed position. In fact, many stars are running at high speed, and some of them are running at a speed far beyond people's imagination.
In p>25, astronomers in the United States discovered a star, and its speed was over 2.4 million kilometers per hour. Astronomers speculate that this star runs so fast, probably because a star met a supermassive black hole in the center of the Milky Way about 8 million years ago. However, this high-speed star will eventually fly away from the Milky Way, which is also the first star discovered by humans to "escape".
13 The hottest white dwarf editor
The sun is the source of light and heat on the earth, but when we face the starry sky at night, we only see glimmering light, but we don't know that some of the stars also emit light and heat.
the surface temperature of a white dwarf star numbered H154+65 (a high-density remnant of a dead star) is as high as 2, degrees Celsius, which is 3 times the surface temperature of the sun.
14 The Biggest Star Editor
Cradle of Stars
Haishan Erxing is a rare Supergiant star, whose mass is 12-15 times that of the sun, ranking first in the Milky Way. Haishan 2 is located in the "star cradle" of the Milky Way, which has always been the place where many stars were born. Although the light is no longer shining now, this superstar has also shone. When the brightness is the highest, people can see it during the day.
Two most beautiful galaxies (3)
The most beautiful galaxy
Stars are synonymous with romance. At the edge of the Milky Way, 3, light years away from the Earth, there are two giant galaxies that are performing the "tango".
these two galaxies are composed of billions of stars and gas clouds, both of which are spiral. The stars, gas and dust of the larger galaxy on the right form an "arm", which surrounds the smaller galaxy on the left and slowly poses various graceful dances under the interaction.