One of the 88 constellations-Sagittarius

Sagittarius is the third smallest constellation in the whole day (only Sagittarius and the Southern Cross are smaller than it), belonging to the northern constellation, located in the Milky Way galaxy south of Cygnus and north of Aquila. Adjacent to the fox constellation. This is one of the ancient Ptolemy 48 constellations. It was smaller than it is now, accounting for only 4 square degrees. The brightest star is left 75 (Sagittarius γ). You can see the complete Sagittarius in the vast area north of 69 degrees north latitude, but you can't see it at all in the area south of 74 degrees south latitude. On the night of July 16 every year, the center of Sagittarius passes through the upper transit, and the best observation month is August.

Sagittarius is surrounded by the following constellations, from north to clockwise: fox, five immortals, eagle and dolphin. Several stars in Sagittarius are arranged in the shape of a flying arrow, and the arrow body is just perpendicular to the direction of the three stars of Altair (also known as the shoulder pole star), so it is easy to identify. Sagittarius comes into view when it moves from the alpha star of Aquila to the beta star of Cygnus (third-class star) with a visual field of about 10. Sagittarius γ is the brightest star in the constellation, with the middle name left 75 and apparent magnitude 3.47. , the distance is 190 light years. The middle name of Alpha Sagittarius is Zuo Qi 1, the apparent magnitude is 4.37, and the distance is 6 10 light years. The middle name of Sagittarius β is left flag 2, which makes the brightness 4.37 and so on, and the distance is 640 light years. The above three stars are all superstars. The middle name of Sagittarius is Zuoqisan, which is an irregular variable star with an apparent magnitude of 3.75 to 3.83, 570 light years away.

Sagittarius has a famous globular cluster-m 71,which lies between the γ star and δ star in Sagittarius. It is a globular cluster with brightness of 9 and apparent diameter of 6. Because the apparent diameter is too small, it looks like a nebula from binoculars. For a long time, many astronomers thought that M7 1 was more like a dense open cluster, just like M 1 1, but now people have agreed that M7 1 is indeed a loose globular cluster. Its apparent magnitude is 8.3, and it is 13000 light years away.