At night, we can see lots of stars in the sky. There are so many stars that we cannot count them all. Stars look like they are little because they are very far away. But stars are actually very big! Stars are huge balls of hot gas. They glow because they are so hot.

During the day, we see a bright yellow star shining in the sky. It is our sun! Our sun gives us heat and light. It looks to us like the sun moves across the sky during the day, but it is really the earth that is moving around the sun.

To us, the sun looks much bigger than any other star. But many of the stars that we see at night are actually much bigger than the sun. The stars we see at night look smaller because they are much farther away than the sun.

Fun facts about stars：

The color of a star can help us tell how hot the star is. Red stars are hot. Yellow stars are hotter than red stars. Green stars are hotter than yellow stars.

At the moment of 9:43 a. m., on Tuesday, June 23rd, 2020, at the Xichang Satellite Launch Center (卫星发射中心) in Sichuan Province, the last satellite of the third-generation network (第三代导航系统) was sent into space. It is the 55th member in the family of BeiDou. It belongs to China’s Beidou Navigation Satellite System (BDS北斗卫星导航系统). So far, all the members of Beidou, 59 satellites, have been launched into space. With the development of China, we have already owned three other famous satellite launch centers — Jiuquan, Taiyuan and Wenchang.

Now, the satellite works well with other Beidou satellites together. So far, China has completed the third-generation network of China’s BDS. It was a newmilestonein the nation’s space research work. The launch showed that our country has completed our largest space-based system. It’s one of four international net-works, including the United States’ GPS, Russian’s GLONASS and the European Union’s Galileo.

BDS has been widely used as public resources in our daily life. It has been shared by the whole world. It will provide more services around the world. BDS is the common wealth of the development of human beings.

Star scientists have taken the first ever picture of a black hole, which is from a far away galaxy (银河系). It is 40 billion km across-three million times the size of the Earth-and has been described by scientists as "a monster".

The black hole is 500 million trillion km away and was photographed by a network of eight telescopes (望远镜) across the world.

Details have come out today in Astrophysical Journal Letters. Prof Heino Falcke, says "It is one of the heaviest black holes that we think there is. It is a real monster."

The picture shows a quite bright "ring of fire", as Prof Falcke describes it. The brighthalois caused by superheated gas fling into the hole. The light is brighter than all the billions of other stars in the galaxy-which is why it can be seen so far away from Earth.

The dark circle at the centre is the point at which the gas enters the black holes, which is an object that has such a large gravitational (万有引力的) pull, not even light can escape.