How to judge Jupiter, Mars, Venus and Saturn with naked eyes?

First, let's see which areas in the sky are likely to see them. The orbits of the nine planets around the sun are not in the same plane, but inclined to each other. If the earth's orbital plane, the ecliptic plane, is taken as the standard, the orbital inclination of all major planets is less than 7, and only Pluto has an orbital inclination greater than 7. That is to say, the orbital inclination of the big planets that can be recognized by the naked eye is within 7, or the big planets that can be recognized by the naked eye always appear in the sky area within 7 north and south of the ecliptic, and will not appear in other parts of the sky. So as long as a particularly bright celestial body is found in the zodiac 12, it can be roughly determined that it is a big planet. About the zodiac 12 constellation, we can get familiar with it with the help of celestial globe or active star map, so I won't go into details here. In addition, there are nine planets' positions and brightness on any date in the annual astronomical calendar, and every issue of Astronomical Enthusiast magazine will publish the next month's Important Astronomical Forecast and Dynamics of the Sun, Moon and Planets. With the help of these materials, we can easily determine which bright stars in the sky are big planets on any date.

Through continuous observation of the starry sky, it is found that planets often have obvious relative motion on the sky background composed of stars, which is the most reliable way to identify planets with naked eyes. The "travel" of planets is only relative to the "constancy" of stars. Because the planet and the earth revolve around the sun together, their speeds and periods are different, so the planet can't keep a certain relative position on the background of stars, or the planet always walks between constellations and won't stay still in which constellation for a long time. On the background of stars, the displacement speed of planets varies greatly, the fastest is Venus, followed by Mars, Jupiter is slower, and Saturn is slower than Jupiter.

Among the big planets that can be recognized by naked eyes, the brightness of five planets, namely gold, wood, water, fire and earth, is brighter than that of stars such as 1. In the sky, their appearance is very noticeable. Uranus can also be observed under good observation conditions.

Details are as follows:

Venus: The brightest star in the whole day (except the sun and the moon) is very white. Its brightness is six or seven times brighter than Jupiter's brightest, and it is within 48 degrees before sunrise. You won't see it in the sky at night.

Mars: It has a unique fiery red color.

Mars, Jupiter, Saturn and Uranus are all located outside the earth's orbit and are called extraterrestrial planets. Seen from the earth, extraterrestrial planets sometimes form an included angle of180 with the earth and the sun (but not necessarily in a straight line). If the sun is in the middle at this time, it is called "conjunction", and the planet of "conjunction" is in the same direction as the sun, of course we can't see it; If the earth is in the middle at this time, it is called "Chong", and the planet and the sun are located on both sides of the earth. When the sun goes down, they rise from the east, and when the sun rises, they set from the west and stay above the horizon for the longest time (visible all night). At this time, the planets can be seen not only in the sky at night, but also in the noon circle and its nearby ecliptic. Except for "closing day" and "market day", other dates are usually: from closing to market, visible in the middle of the night; From rushing to closing, you can see it in the middle of the night.

To sum up, to identify a planet with the naked eye depends not only on the sky area where it appears, but also on its brightness, color, light stability, apparent displacement, appearance direction and time spent above the horizon. As long as we pay attention to the above factors when observing the starry sky, we can easily identify the big planets from the stars with the naked eye. Of course, it takes experience to identify planets with the naked eye. As long as you can persevere, you can be accurate. Even, we can apply the above principles analogously and use astronomical telescopes to identify and discover new planets or asteroids.