[1] transit of venus is a celestial phenomenon in which Venus runs between the sun and the earth, and the three are in a straight line, and Venus blocks part of the sun. Therefore, transit of venus is also called a small solar eclipse. Transit of venus can be divided into five stages: circumscribed, inscribed, inscribed, inscribed and circumscribed. Hours are usually used to calculate the time in transit of venus (2004 and 20 12, lasting about 6 hours). In principle, it is similar to an eclipse, although Venus is almost four times the diameter of the moon. Venus that we see from the earth is much smaller because it is farther away from the earth. Before modern astronomy, people used parallax to measure the distance between the sun and the earth by observing transit of venus. Venus is the inner planet of the earth. It takes 224.438+0 days for the earth to go around the sun, and 365.256 days for the earth to go around the sun. The rendezvous period is 583.92 days, that is, the time interval between two consecutive eclipses of Venus.

classify

Transit of venus can be divided into two types: one is transit of venus and the other is descending node, which happened around June 8th. At that time, Venus will cross the sun from north to south (ecliptic); One is transit of venus, which occurred around 65438+February 10. At that time, Venus will cross the ecliptic from south to north. It is generally believed that

Transit of venus (3 photos) shows that Venus appears alternately in pairs at the descending node and transit of the ascending node, and the number is equally divided. In fact, they are not equal in quantity, that is, the transit of venus of the descending intersection is more than that of the ascending intersection. From 902 to 1984, there were 32 occurrences in transit of venus, including 18 occurrences in transit of venus and descending node, and only 14 occurrences in transit of venus. The reason why the intersection of descending node and transit of Venus is more than the ascending intersection is that the transit of Venus is in descending node (around June 8), and Venus is far away from the earth, reaching 432 10000 km; In transit of venus, the ascending node, Venus is close to the earth, only 39.47 million kilometers. Under the same conditions, the farther away from the earth, the greater the possibility of transit of venus.

circulate

Transit of venus takes two transits as a group, with an interval of 8 years, but the interval between the two groups exceeds 100 years. The last group of transit of venus before 2004 occurred in February of 65438+ 1874 and 1882. The first transit of venus in 2 1 century took place on June 8, 2004, and the other one in this group will take place at 6: 09 on June 6, 20 12. The next time is 2 1 17 and 2 125. The interval is 105. Each type occurs every 243 years, because the 243 sidereal year (365.25636 days) on Earth is 88757.3 days, and the 395 sidereal year (224.5438+0 days) on Venus is 88756.9 days. So after this time, Venus and the Earth returned to the same position in their respective orbits at almost the same time. Because Venus and the Earth's orbits around the sun are not on the same plane, the transit of venus phenomenon does not happen every time Venus and the sun meet. Generally speaking, the earth passes through the ascending intersection of Venus orbit around 12 every year, and passes through the descending intersection of Venus orbit around June 8 every year. Therefore, transit of venus can only happen around these two dates. Transit of venus has cycles of 8 years, 243 years and 25 1 year. The 8-year period is equal to 8 Earth years (365.256 days), 13 Venus years (224.7438+0 days) and 5 rendezvous periods (583.92 days). The period of 243 years is equal to 243 Earth years, 408 Venus years and 157 rendezvous periods. If you choose 8 years at will, you can get two transit of venus, such as 1874 to 1882. If you choose 243 years arbitrarily, you can get five transit of venus, such as 1874 to 2 1 17, and if you choose 25 1 year arbitrarily, you can get six transit of venus, such as 1874 to 21/kloc-. The interval between the two transit of venus events is 8 years,1210.5 years, 8 years, 105.5 years, 8 years,1210.5 years, 8 years, 105.5 years. The sum of 8,121.5,8 and 105.5 is equal to 243, which is the most basic and stable period in transit of venus. Judging from the long period of transit of venus, Venus descending node (Ascending Point) moves from west to east. On June 8, 2004, transit of venus was two days later than transit of venus on June 6, 176 1, that is, in 243, the downward intersection of Venus moved forward (east) for two days. Astronomers in China discovered the 8-year Venus cycle more than 2,200 years ago. Cheng Shu wrote in the Western Han Dynasty's "Five Stars": "Five out, eight years old is the sky, and the re-camp room leaves the east in the morning." In other words, the five rendezvous periods of Venus will wait until eight years, which means that Venus will reappear in the same constellation at the same time eight years ago or eight years later. This shows that ancient Chinese astronomers have mastered the laws of Venus and the Earth. As can be seen from the cycle of transit of venus above, most people can only see transit of venus twice at most, not at least once, and only a few people can see it four times.