Messier 22

A big group of stars sits in space. It is called M22. It is very bright in the night sky.

This group has many stars. One man found about 70,000 stars in it. The center is very thick with stars.

It is far away from Earth. It is near a shape called the Teapot. You can see it in the summer sky.

It also has a glowing cloud of gas. This cloud comes from a big star. There are also black holes in the group.

It is a very special place in space. Do you like to look at stars?

M22 is a big group of stars. We call this a globular cluster. It sits in the Sagittarius constellation. This group is very bright in the night sky. You can see it from many places in the north.

This cluster is about 10,600 light-years away. A light-year is the distance light travels in one year. M22 is quite wide. It is about 99 light-years across. In 1930, a man named Harlow Shapley studied it. He found about 70,000 stars inside. He saw that the center is very thick with stars.

M22 has some very rare things. It has a planetary nebula. This is a glowing cloud of gas from a big star. The cloud is likely 6,000 years old. It has a blue star at its center.

Scientists also found black holes there. They used a radio telescope in New Mexico. They found two black holes. These holes are 10 to 20 times the mass of our sun. There may be up to 100 black holes in the cluster. These black holes might help make the center so thick.

Messier 22 is a huge group of stars. Scientists call this shape an elliptical globular cluster. It sits in the Sagittarius constellation. You can find it near the galactic bulge. This is a busy part of our galaxy. It is one of the brightest globular clusters in the sky. People in the northern hemisphere can see it well. It stays low in the southern sky for them. This is because its position is 24 degrees south of the equator.

This cluster is about 10,600 light-years away from Earth. It spans 32 minutes on the sky. This means its width is about 99 light-years. The stars inside are very crowded. Harlow Shapley found about 70,000 stars in 1930. He saw that the core is very dense. This means the stars are packed tight in the middle. Other scientists like Halton Arp studied it later. They looked at it in 1959.

Many people helped find and study M22. Johann Abraham Ihle discovered it in 1665. Charles Messier added it to his list in 1764. Later, James E. Hesser and his team studied it in 1977. They looked at the red giant branch. This is a line of stars that are turning red. This part of the cluster has many different colors. It has also had 32 variable stars recorded in it.

There are rare things hidden inside this cluster. M22 is one of only four clusters with a planetary nebula. A planetary nebula is a glowing cloud of gas. This gas comes from a massive star. This specific cloud is likely 6,000 years old. It has a blue star at its center. Fred Gillett found this using a satellite in 1986. He and his team found its true nature in 1989.

Scientists also found something very heavy there. They used the Very Large Array in New Mexico. They also used the Chandra X-ray telescope. In 2012, they found two black holes. Each one is 10 to 20 times the mass of our sun. There might be 5 to 100 black holes in the cluster. These black holes might interact with stars. This could explain why the core is so thick. It shows that black holes stay in clusters well.

Messier 22, also known as M22 or NGC 6656, is a massive group of stars. Astronomers call this shape an elliptical globular cluster. It is located within the constellation Sagittarius. The cluster sits near the galactic bulge, which is a busy region of our galaxy. M22 is one of the brightest globular clusters visible in the night sky. It is particularly easy to see from mid-northern latitudes. These locations include Europe, North America, Korea, and Japan.

This cluster is quite large and spans 32 minutes of the sky. Based on its estimated distance, its diameter is about 99 light-years wide. M22 is relatively close to Earth at a distance of 10,600 light-years. Even though it is close, its light is limited by dust extinction. This means dust in space blocks some of its brightness. This results in an apparent magnitude of 5.5. Because its declination is nearly 24 degrees south of the celestial equator, it stays low in the sky for northern viewers.

Scientists have studied the structure of M22 for a long time. In 1930, Harlow Shapley conducted a careful study of the cluster. He estimated that it contains roughly 70,000 stars. He also discovered that the cluster has a very dense core. Other researchers, including Halton Arp and William G. Melbourne, continued these studies in 1959. By 1977, James E. Hesser and his team began intense scrutiny of the cluster. They focused on the red giant branch, which is a sequence of stars in the cluster. This branch shows a large spread of different colors.

Many people have contributed to our knowledge of M22 over the centuries. Johann Abraham Ihle first discovered the cluster in 1665. Later, Charles Messier included it in his famous catalog of comet-like objects in 1764. The cluster also contains 32 known variable stars. These are stars that change in brightness over time. Because M22 sits in front of part of the galactic bulge, it is useful for studying microlensing. This occurs when the gravity of the cluster acts like a lens on stars behind it.

One of the most unusual features of M22 is a planetary nebula. A planetary nebula is an expanding, glowing cloud of gas from a massive star. M22 is one of only four globular clusters in our galaxy known to have one. This nebula is called GJJC1. It likely has an age of only about 6,000 years. A blue star sits at the center of this gas cloud. Fred Gillett and his associates first noted this light source using the IRAS satellite in 1986. They confirmed its true nature in 1989.

Recent discoveries have also revealed heavy objects hidden within the stars. In 2012, researchers used the Chandra X-ray telescope and the Very Large Array in New Mexico. They found two black holes inside the cluster. Each black hole has a mass between 10 and 20 solar masses. Scientists estimate there could be between 5 and 100 black holes in M22 in total. These findings suggest that black holes are not easily ejected from clusters through gravity. This discovery helps us understand how clusters evolve over time.

The presence of these black holes might explain why the cluster has such a large core. Interactions between the stars and the black holes could be the cause. This connects the study of individual stars to the study of massive, invisible objects. By studying M22, astronomers learn more about the history of our galaxy. They also learn how gravity shapes the largest groups of stars in the universe.