Many people still don't know what a planet is and what a star is, except that there are many stars in the sky, bright and dark. One of them is the most eye-catching, which often appears in the sky at dusk or in the east at dawn. This star is very bright and beautiful. Sometimes when the sun comes out or hasn't set, it hangs in the sky, as if it were a loyal guardian of the sun, following closely.
Of course, sometimes I may be sent by the sun on a business trip. I haven't seen any trace for a while, but I will always come back, still so bright and loyal. What star is this? That star is the nearest planet to the earth ~ Venus.
Venus has two most famous names since ancient times: Venus and Pleistocene. The ancients thought these were two stars at first, but later discovered that they were the same star ~ Venus, also called Taibai Venus. When Venus appears in the western sky at sunset, it is called Chang Geng Star. When Venus appears in the dawn sky and seems to be calling for dawn before the sun comes out, it is called the morning star.
Venus and the sun sometimes appear in the eastern or western sky at the same time, because the sun is not strong in the morning and evening, and Venus is the brightest star in space, so the sun can't hide at that time.
the closest distance between venus and the earth is about 421km, and the farthest distance is about 2.417km. The difference between apogee and perigee is so much because the Earth and Venus have their own orbits, and the revolution speed is different, so when the two planets move to the same side of the sun, the distance is very close; And when the two planets move on their respective sides of the sun, there is a sun between them, which is far away. Venus is the brightest star in the sky because it is close and has high albedo.
Venus and the Earth are both planets in the solar system, and they do not glow by themselves, but shine by reflecting sunlight. Venus is about the same size as the earth, with a diameter of 12642km and a diameter of 1214km. Venus is slightly smaller than the earth, accounting for 95.74% of the diameter of the earth.
The albedo of Venus reaches 76%, which is much higher than the albedo of the earth of 36.7%. The so-called albedo is the ratio of the reflected radiation to the received radiation. Venus only digested and absorbed 24% of the solar radiation, and the remaining 76% was reflected back into space. The solar radiation mainly illuminates celestial bodies in the form of visible light, so the higher the reflectivity, the brighter the corresponding celestial bodies.
Venus is the closest extraterrestrial body except the moon, and it is about the size of the earth, and has a high albedo, so it becomes the brightest celestial body in the night sky, reaching the apparent magnitude of -4.6 at the brightest. Sirius, the brightest star in the night sky, is only -1.46 at the brightest time.
magnitude means that the smaller the value, the brighter it is, the larger the value, the darker it is, and there are negative numbers, and the more negative it is, the brighter it is. There is a difference of 2.512 times between the intensities, so the magnitude difference is 2.512 as the base and the magnitude difference as the power, so Venus is about 18 times larger than Sirius. So why does Venus sometimes appear in the west and sometimes in the east?
This is because the earth rotates from west to east all the time, once every 24 hours. In this way, all the stars in the sky look as if they are revolving around the earth. Every night, the stars, like the sun, rise in the east and set in the west. There is a star in the direction of the earth's rotation axis, and that is Polaris or invivo.
Both the Earth and Venus have their own orbits, which are on the ecliptic plane. Because of their different orbital speeds, the distance and orientation from the Earth change every day, so Venus' position in the sky at the same time at night is different. When it runs to a position close to the sun from the earth's line of sight, it will become a morning star and a long gengxing; Running farther away from the other half of the earth will dim down; Running into the sun's light or blocked by the sun, or Venus completely facing away from us, we can't see it.
Planets move rapidly and change greatly in the sky. This is because the planets are very close to us, and the changes are obvious relative to the stars in the sky, which is why they are called planets. Besides Venus, all other planets and the moon have this property, all of them? Follow? The characteristics of the sun are only that the brightness of planets farther away from us is much weaker, and our attention is much less when we eat melons and look at the night sky with the naked eye. The planet itself does not shine, but it is the brightest star in the night sky.
Besides Venus, the brightest planets in the night sky include Jupiter, Mars, Saturn and Mercury. Jupiter and Mars are the bright stars in the night sky, second only to Venus. At the brightest, the apparent magnitude can reach -2.9. Saturn's brightness is slightly weak due to its long distance, and its apparent magnitude can reach -.4 at its brightest.
because mercury is close to the sun, it is often hidden in the sun's brilliance, so it is hard to see. There is a historical allusion that the greatest regret of astronomer Copernicus's life is that he didn't see Mercury. In fact, although the observation of mercury is difficult, it can still be observed. Because when mercury is brightest, the apparent magnitude can reach -1.9, which is brighter than Sirius.
Copernicus didn't observe it, and later generations analyzed it because Copernicus was in a high geographical latitude, and in recent thousands of years, due to the precession of Mercury, it was in an angle that was difficult to observe in the northern hemisphere. If we can see mercury, we will see the same scene as Venus, and we will see it before sunset and dawn.
So China also named Mercury in ancient times? Morning star? And? Twilight star? It's just not as famous as Venus. The distant planets Uranus and Neptune can't be seen by naked eyes, because the resolution limit of human vision is 6 stars, and the apparent magnitude of these two planets exceeds 6. Apart from these planets, thousands of stars visible to the naked eye in the sky are all stars.
because the stars are too far away from us, they are moving, but relative to our distance, this movement is too weak. It seems that it has not changed for thousands of years, and it is still in that position, as if it is eternal, so it is called a star.
For example, the nearest star visible to the naked eye is Sirius, which is 8.6 light years away. A light-year is about 9.46 trillion kilometers. Even if this star moves relative to the earth at a speed of 1 kilometers per second, it can only change by 3.2 billion kilometers a year, and it takes 3, years to change by one light-year. Most of the stars are more than 1 light years away, and this change can't be distinguished by the naked eye for hundreds of thousands of years in a short period of time.
Planets and stars are two celestial bodies with completely different properties. Stars are huge, relying on internal nuclear fusion to glow and radiate energy into space. There is only one star in our solar system, the sun. The sun occupies 99.86% of the mass of the whole solar system, and all the planets and small celestial bodies add up to .14%. The mass of the earth is only one-third of that of the sun, and its volume is one-tenth of that of the sun. The ratio between the earth and the sun is like a mung bean and a football.
There are about 4 billion stars in the Milky Way, and the whole universe is estimated to have as many as 1 trillion galaxies.
This is a brief and basic picture of the movement of the sun, moon and stars in the sky, and it is also a picture of seeing the brightest star near the sun. Welcome to the discussion and thank you for reading.
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