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.

According to Ken Croswell, The Sun shines all the time. It shines during the day when we see it, and even at night when we don’t.

As the Earth turns, sometimes we face the Sun. That’s when we get day. When the Earth’s spin (自转) turns us away from the Sun and we are in the Earth’s shadow, we get night. When people on the opposite side of the Earth face the Sun, those people have day while we have night.

The Moon is a different story. Unlike the Sun, it doesn’t make its own light. Moonlight is actually the Sun’s light reflecting (反射) the Moon back to us.

The Sun lights up only the side of the Moon that faces the Sun. At Full Moon, the Moon is on the opposite side of the Earth from the Sun. Then the side of the Moon facing the Earth is all lit up. During Full Moon, the Moon rises around sunset (日落), shines all night, and sets around sunrise (日出). Since the moonlight is so bright, you can sometimes see it during the day, too. A few days before Full Moon, if you look east in the afternoon, you may see the Moon in the sky. After Full Moon, you may find it if you look west in the morning.

The Moon is most difficult to see at New Moon, when its orbit (轨道) puts it between the Earth and the Sun. Then, the side of the Moon facing the Earth is dark and we can’t see the Moon at all.

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In the universe, as we know, there is the sun, the moon, the earth and many stars. Through our geography lessons, we know the earth goes around the sun, and the moon goes around the earth. We have day and night because the earth keeps turning all the time. When our part of the earth turns to the sun, it is day. When our part of the earth turns away from the sun, it is night.

Just because the moon is closer to the earth than the sun, it looks much bigger than the sun. Big things look smaller when they are farther, and small things also look bigger when they are nearer.

The sun is bright enough to give out very strong light. The moon can’t give out any light at all, but it looks quite bright too. Why? In fact, the light from the moon comes from the sun. The moon looks much bigger and brighter than the stars. But actually the stars are much bigger and brighter than the moon. They look smaller than the moon also because they are farther away from the earth.

There are still many other planets in the solar system (太阳系). All of them move round the sun. But of all these planets, only on the earth there are living things and people can only live on the earth too. At 9:00 am on October 15th, 2003, Chinese pilot Yang Liwei was sent up to space. He stayed there for 21 hours. It was the first time for Chinese to get into space.