The world got a glimpse（一瞥）of one of the greatest mysteries of our universe（宇宙）on April 10. That's when the first image of a black hole was shown to the public. The picture was created by a network of eight radio telescopes（射电望远镜）.

“We have seen what we thought was unseeable ,"says Shep Doeleman. He led the effort to create the image.

The black hole is at the center of galaxy（星系）named Messier 87,some 55 million light-years from the earth，and is 6.5 billion times the mass of the sun.

The image shows the gas，dust，and stars that move around the black hole before disappearing into it. It does not truly show the black hole，because not even light can escape its gravity. Black holes, like vacuums, suck（吸）in everything that gets too close.

①Most people have a place to call home on Earth. What about in outer space? The International Space Station(ISS) became our first “home” in space in 2000. It welcomed its first crew(队) that year, paving the way(铺平道路) for 20 years of future research.

②“You just have this impression that we’re all citizens(公民) of not a country, but of the planet,” former NASA astronaut Scott Kelly told National Geographic about working in ISS. “We’re all in this thing called humanity(人类) together.”

③Over the past 20 years, the ISS has mainly been used as a science lab, hosting 241 people from 19 countries, according to NASA. They have gone on spacewalks, done research on how space affects the human body, and even grown plants in space.

④ ▲ . For example, the station’s water purification(净化) technology has been used in poor areas to provide clean drinking water. The station also helps to warn us of natural disasters(灾难), such as earthquakes.

⑤However, after being our home in space for over 7,000 days, the station is starting to get old. It has leaked(泄漏) air a few times. Scientists think that the station can keep working until 2024. After that, scientists will bring it down to Earth. It is believed that Earth’s atmosphere(大气) will burn up most of the station. Other debris(残骸) will fall into the Pacific Ocean.

⑥In the future, space will be home to more stations like the ISS. NASA is building a space station that is smaller than the ISS near the moon. Also, China will have its own space station up in 2022.

(a. gone on spacewalks        b. provide clean water for poor areas       c. stopped earthquakes       

d. learned how space affects the human body            e. grown plants )

The idea of life in outer space has been talked about for a long time. Some scientists say that life development on Earth was far too unlikely for it to have happened anywhere else. Things had to be perfect for us to make it on this planet.

Other scientists say that space is too big. Stars and other planets are far too numerous for there to be no other life in the universe.

For many years, there have been reports of visitors from other planets. People all around the world have claimed to see alien spaceships or even aliens themselves.

There have been glimpses of these so-called UFOs (unidentified flying objects) flying through the air and they have even ben captured on video. Some Americans believe that the U.S. Army found an alien spaceship crashed in the desert and then lied to the press about it. Although these sightings may be true, scientists have not found significant evidence that aliens exist.

If you go out into the countryside on a clear night and look up, you can see thousands of stars. Those stars make up a tiny part of our universe. There are more stars, planets, and galaxies than we can count. Even the smartest scientists can’t even come close to defining how big space is. The number of possible stars and planets out there is bigger than our ability to count. If we are really on the only planet that can sustain life, then we are very special in a universe full of amazing things.