What's the name of the nebula in Cancer?

Hello, the landlord, the following is the relevant information: Cancer is in the west of Leo and the snake head is in the north. It is the darkest constellation in the zodiac, and the brightest star in the constellation is only 93.8m, so you can't see the shape of a crab at all. This may be because Hercules had already hit it with a stick.

Center position: 8: 00 right ascension, 10 minute, 20 degrees right ascension. Gemini East, Leo West. There are four brighter stars in the constellation, and there is an open cluster M44 (Ghost Cluster).

The fourth house of Cancer Palace. The longitude of the Yellow River varies from 90 degrees to 120 degrees. It originally came from Cancer, hence its name. Every year around June 22nd, the sun comes to this palace. At this time, the solar term is the summer solstice, so the summer point is also called "the first point of Cancer Palace". Near the Delta Star in the center of Cancer (or between the two bright stars of Leo Xuanyuan XIV and Gemini Beta), people with good eyesight can see a small white fog, which was called "corpse gas" in ancient China. The book describes it as "like a cloud Feiyun, like a star but not a star, just seeing gas." It was not until the invention of the telescope that people observed that it was originally a cluster, which was called "hive cluster" in astronomy. This cluster has more than 200 members and is 520 light years away.

Astronomically speaking, star clusters can be divided into two categories, one is the "globular cluster" in Ursa Major, and the other is the "open cluster". These clusters are irregular in shape and generally distributed on silver disks. Astronomers have discovered more than 1000 open clusters in the Milky Way. They estimate that the number of open clusters in the whole galaxy must exceed 10000.

Honeycomb cluster

Praesepe is a member of the open cluster, located in Cancer. Named for its location in a haunted house. Also known as hive clusters, it accumulates corpse gas. China called it corpse gas in ancient times. It is numbered M44 in the messier catalogue. The size of the ghost cluster is less than 10 parsec, and there are more than 200 member stars. The total mass is more than 200 times that of the sun, and its center is about 160 parsec from the sun, which is much farther than the Bi cluster. Ghost cluster is a moving cluster, which is moving away from the earth, and its speed and direction are almost the same as that of Bixing cluster. Galileros confirmed this "hazy" celestial body for the first time. He recorded: "The nebula called Praesepe is not just a star, but a collection of more than 40 small stars." Later, it was added to his catalogue on March 4 1764. M44 also contains a unique blue star. Among its member stars, there are eclipsing binary star-Cancer TX, a star with metal absorption line-Cancer ε, and several 7-8 shield Delta variables, all of which are in the early post-main sequence. Check out our list of brightest stars in M44.

Ghost clusters are classified by trumpler as I, 2, R (according to Kenneth Green Jones), and the classification of Sky Catalogue 2000 is II, 2, M, G? Tz divides it into type ii, type 2 and type R.

As mentioned in the description of Orion nebula M42, it is unusual for messier to add ghost clusters (together with Orion nebula M42/M43 and Pleiades cluster M45) to his catalog, and the reason may still be worth considering.