How often does 12 meteor shower occur? When does the Pisces meteor shower appear?

Every time a comet returns to the sun, it will peel off some substances and scatter them in space under the action of the solar wind. When the earth encounters these substances, it will see meteors appear radially. This is called a meteor shower. Meteor shower is not like rain as expected. As long as all meteors come out from one radiation point, it can be considered as a meteor shower. There are nearly 40 meteor showers every year, among which 10.4 is the quadrant meteor shower, April 22 is the Lyra meteor shower, and August13-/kloc-0.4 is the Perseid meteor shower, 165438+ 10/0.

Activity range of Pisces meteor shower: September1-30; Maximum time: September 19 (Sun Huang Pingjing177); ZHR = 3； Radiation point: Right ascension = 005, and declination =-01; Radiation point drift: See Table 6; Speed = 26 km/s;

This group, which is often regarded as the "essence of September", like other groups this month, is very lacking in observation. It seems that its radiation points are scattered, and we confirm that it has double radiation points through some data.

In the 1 9th century, this set of observation data was only observed twice, both of which were observed by William F. Denning. He observed at 1879 and 1885 respectively, and the radiation points were located at1degree right ascension, declination -5 degree right ascension and declination -2 degree respectively.

It was first officially observed by Kuno Hoffmeister. After analyzing the observation data of German observers in 1908 and 1938, he pointed out that this group was active between 16 August and 18 October, with the maximum value appearing in 12 September. Hoffmeister described this group as very weak and divided it into two radiating points. Hoffmeister didn't give an accurate description of his South League and North League, he only gave a table. Among them, it is impossible to confirm whether the second largest value of No.29 is the product or combination of the Northern Group.

After 1890, photography was introduced into the study of meteors, but the most famous one should belong to the Harvard Meteor Project carried out by 1952- 1954, which included the orbits of more than 2,500 meteors and provided a huge database for future meteor research. 197 1 year, Bertil-Anders Lindblad conducted a study to find out the orbits of those active meteor groups.

Limbra discovered two groups, which he called "Pisces meteor shower" and numbered "3 1" and "92". Activity 92 lasted for a long time, from August 3 1 to August 2 1 1. The radiation points are located at right ascension 10 degree and declination +6 degree. However, the orbit of this group is far from Pisces in Hoffmeister, but the ascending intersection is 2 1 degree, and the nearest distance is even 0.60 degree. No.365438 +0 is a better candidate-although it is a little later than Pisces in Hoffmeister. After node 65438+1October 13, the radiation point is located at 26 degrees right ascension and 0/4 degrees declination.

1973, Limbra and Allen F. Cook re-studied the document 197 1, and an important discovery was that most of the No.92 meteor belonged to andromedids of 1 1, so in fact No.92 was confirmed as the southern branch of the Pisces meteor shower. But despite this, the authenticity of No.92 is still in doubt.

No.92 in 197 1 has 33 members, but after Andromeda is excluded in 1973, only 14 members remain. G.Kronk of the United States thinks that the remaining 14 meteors are very different from perihelion and have different orbital characteristics of meteor groups. He believes that the so-called 92 is actually a mixture of the Southern Taurus meteor shower and the Perseid meteor shower. According to Crowe's theory, the Southern Pisces is actually composed of two different groups (one of which is the meteor shower in 10), and neither of these groups was mentioned by Hoffmeister, nor was it photographed in the Harvard Meteor Project.

The Pisces meteor shower plays an important role in two radio meteor projects of Z.Sekanina. The first observation was made in 196 1- 1965, and the activity time was from August 14 to June 10.4, and the intersection time was 10.7 September (solar longitude/kloc-0 The activity time of 1968- 1969 is 12 from August to10.7, and the intersection time is September 16. 1 (solar longitude 172.8 degrees. At this time, the radiation point is located at 8.5 degrees right ascension.

According to Cagnina's radar data, it seems that the annual meteor shower reaches its maximum in Pisces in early September, and there is no possibility of a second group. But the first observation and the second observation are slightly different, which should be caused by scattered meteor material.

The Meteor Organization of Western Australia, under the leadership of its chairman, Jeff Wood, made very effective observations. 1979 Despite the influence of the full moon, they still observed that ZHR reached 1.32+/-0.22, which appeared on September 23rd, and the radiation point was located at right ascension 10 degree and declination10 degree. September 1980, 10- 12, appearing at 1 1, reaching 1.24+/-0.26, and the radiation point is located at 4 degrees right ascension and 9 degrees declination. The data of 1980 are divided into north group and south group. On September 1 1-27, the ZHR of the southern group was 2.08+/-0.20, and on May 5-16, the ZHR of the northern group was 2.94+/.