1 . How many things can you see in the night sky? A lot! On a clear night you might see the Moon, some planets, and thousands of stars.
But scientists believe there are some things in the sky that we will never see. We won’t see them with the biggest telescope in the world, on the clearest night of the year. That’s because they are invisible (看不见的). They’re the mysterious dead stars called black holes.
You might find it hard to imagine that stars die. After all, our Sun is a star. Year after year we see up in the sky, burning brightly, giving us heat and light. The Sun certainly doesn’t seem to be getting old or weak. But stars do burn out and die after billions of years.
As a star’s gases burn, they give off light and heat. But when the gases run out, the star stops burning and begins to die.
As the star cools, the outer parts of the star pull in toward the center. The star is squashed (挤压) into a smaller and smaller ball. If the star was very small, the star ends up as a cold, dark ball. If the star was very big, it keeps being squashed inward until it’s packed together tighter than anything in the universe.
Imagine if the Earth collapsed until it was the size of a tiny marble (玻璃球). That’s how tightly this dead star, a black hole, is packed. What pulls the star in toward its center with such power? It is the same force that pulls you down when you jump — the force called gravity. A black hole is so tightly packed that its gravity absorbs everything — even light. The light from a black hole can never come back to your eyes. That’s why you see nothing but blackness.
So the next time, you look up at the night sky, remember: there’s more in the sky than what meets the eye! Scattered (散落) in the silent darkness are black holes — the great mystery of space.
1. What might happen after a star dies?| A．The star might become a black hole. |
| B．The Earth might be hit by the star. |
| C．The sky might become much darker. |
| D．The gravity might totally disappear. |
| A．Its gases run out. | B．It hits other stars. |
| C．It gets too hot. | D．Its light fades away. |
| A．Folded. | B．Crashed. | C．Orbited. | D．Marched. |
| A．Most black holes are too far away. |
| B．We don’t have a powerful enough telescope. |
| C．Black holes can travel as fast as light. |
| D．Light can not escape a black hole’s gravity. |
2 . A new study focuses on K2-18b, an exoplanet(系外行星) discovered in 2018, which orbits a red dwarf star close enough to receive about the same amount of radiation from its star as Earth does from our sun.
Recently, scientists have discovered gas giants that have water in their atmospheres, but this is the least giant planet ever to have water detected in its atmosphere. “The water detection was quite clear to us relatively early on,” lead author Bjorn Benneke, a professor at the Institute for Research on Exoplanets at the Universite de Montreal, told Space.com in an interview.
“Studies have suggested that planets with hydrogen-rich atmospheres could host certain forms of life.” Benneke said. However, “K2-18b’s large atmosphere is extremely thick and creates high-pressure conditions, which likely prevents life as we know it from existing on the planet’s surface.” a news release reads. While these researchers found evidence for liquid water clouds on K2-18b, because of its lack of surface, rain wouldn’t pool on the planet. Without a real surface, so to speak, landing on the planet would also be nearly impossible to land on, especially because the gas is so thick and has such an incredibly high pressure that any Earth-created spacecraft sent there would be destroyed.
Benneke suggests that, possibly, this planet formed by rock absorbing large amounts of gas, “like a vacuum cleaner,” he said. The gas absorbed would have more than doubled the planet and increased its volume Warren eightfood.
To come to these conclusions, the research team analyzed data from Hubble Space Telescope observations that they made between 2019 and 2020 of the K2-18b planet passing in front of its star eight times. This type of research, Benneke said, is leading toward a final goal of “being able to study real, true earth-like planets.” We are not quite there yet, he said, but this is really exciting.”
1. Why is it impossible to land on the K2-18b?| A．It has thin gas. | B．It doesn’t have a real surface. |
| C．It has too much water. | D．It is too far from the earth. |
| A．By releasing gas itself. | B．By receiving radiation from the sun. |
| C．By taking in much gas by rocks. | D．By getting away from the red dwarf star. |
| A．Scientists are making progress in studying real earth-like planets. |
| B．It is impossible for humans to land on other earth-like planets. |
| C．Scientists have succeeded in exploring K2-18b completely. |
| D．The K2-18b planet has passed before its star eight times between 2019 and 2020. |
| A．The exploration of the outer space. |
| B．The study of solar systems’ environment. |
| C．The discovery of the K2-18b planet. |
| D．The research on the K2-18b planet. |
