What do black holes look like? We finally got the answer: they look like dark circles with a bright ring around the outside. Scientists took the world’s first photo of a black hole. The black hole is very far from Earth—about 55 million light years away. This is not the only black hole in the universe.

Black holes are mysterious in the universe. A photo can help us learn more about them. How much do you know about black holes? Try to answer the following questions.

Q: What is a black hole?

A: A black hole comes from a dying star. The star turns in to a small point. The point has much mass and strong gravity (引力) . The strong gravity of a black hole pulls things. The black hole “eats” these things. Black holes can even “eat” light. That’s why a black hole looks “black”.

Q: If black holes are “black”, how do scientists know they are there?

A: We cannot see black holes. But we can see how their strong gravity works on the things around them. A black hole’s gravity pulls dust and gas into it. And if a star is orbiting (绕轨道运行) a point in space, scientists can study the star’s orbit. They can tell if the star is orbiting a black hole.

Q: How did scientists take the picture of the black hole?

A: Scientists didn’t use a camera to take the picture. They used eight radio telescopes in different places across the world. The telescopes got information from the black hole. Scientists used computers to deal with the information. It took them two years to get the final picture.

Q: Will the sun turn into a black hole? And if it does, will it “eat” Earth?

A: The sun won’t become a black hole. According to NASA, it does not have enough mass to turn into one. When the sun dies, it will become a smaller and cooler star. Even if the sun becomes a black hole, Earth would still be safe.

NASA’s space scientists were closely watching a very large asteroid (小行星) that flew past Earth recently.

Asteroid 2015 DR215 was on NASA’s “close approach(接近)” list. But don’t worry, it was a safe distance (距离) away! It was thought to have passed Earth at a distance of 4.1 million miles away. So it was not a dangerous asteroid for us! The asteroid is around 1,600 feet wide, which is three times larger than the Great Pyramid in Egypt. What are asteroids? Asteroids are large space rocks in our solar system (太阳系). Sometimes they are called NEOs-Near Earth Objects. Until today, about 26,000 asteroids have passed Earth, according to NASA.

There are lots of asteroids that NASA watches all the time. They are usually 140 meters or above and can be a threat (威胁). The last big asteroid to actually hit Earth was 66 million years ago. This one caused the dinosaurs to die out. In fact, many smaller asteroids fly to Earth the whole time. But because of their much smaller size, they get burnt up in the atmosphere (大气层) before they hit Earth. Therefore, they can’t bring serious results.

We live on Earth. It’s our home. But how much do you know about it? Let me tell you something about our Earth. The Earth is like a huge ball. Like the other seven planets（行星）, the Earth is running around the sun. It’s the third nearest one to the sun. It takes the Earth about 365 days to run around the sun. At the same time, the Earth is going around itself. If you are in space, you can see lots of white clouds over the surface（表面）of the Earth. Through the clouds, you can see the blue colour of the oceans, and the brown colour of the land. About 70% of the Earth is covered with water. Why do we have day and night? When the half of the Earth is facing the sun, it’s daytime. As the Earth turns, and this half is away from the sun, night is coming. And it’s daytime for the other half.