2 . Mars is the fourth planet from the Sun and the second smallest planet of the Solar System.

It is around two times smaller than Earth with a diameter of 6,779 km. If you stand on Mars and look at the Sun, it will appear about half the size we see it on Earth. Mars is widely known as the red planet. Its red appearance is caused by the rusty iron in the ground.

In many ways, Mars can be considered Earth’s brother. On Mar’s surface, we have discovered the biggest mountain in the Solar System. It is named Olympus Mons, and it is three times bigger than the largest mountain on Earth. A day on Mars is also a little longer than a day on Earth. It lasts about 24.6 hours. A year on Mars, however, or the time that takes for the red planet to circle our Sun, lasts about 687 Earth days. That is almost twice as long as a year on Earth !

In the 19th century, it was believed that life on Mars existed. An astronomer said that he “found” straight lines on Mars’s surface. Many people believed that those were the work of clever life as the straight lines were most likely to be canals for irrigation.

However, as more advanced telescopes were built, it was found that the straight lines were an optical illusion.

To this day, humans are still trying to find out whether there was life on Mars!

Stargazing（观星）takes imagination. People who love stargazing see the stars as shining spots in a dot-to-dot（点对点）drawing game. They imagine lines that connect groups of stars called constellations. A constellation is a group of stars that looks like a person, an animal, or an object.

The constellation Orion is known as the hunter, after a hero from ancient Greek stories. To find Orion, first find the Big Dipper. The Big Dipper looks like a huge cup with a long handle. After you find the Big Dipper, turn around. There’s Orion! He is outlined by four bright stars that form two triangles. The tips of the triangles seem to come together. Where they meet, there are three more bright stars.

Different kinds of stars are in the constellation Orion. The star Betelgeuse makes Orion’s right shoulder. Betelgeuse is an Arabic word that means “shoulder of the giant（巨人）.” The star itself is so huge that it is called a supergiant. Its diameter is 400 times greater than that of our sun. Betelgeuse is considered a cool star. It is probably not as hot as our Sun. Rigel is the star that makes Orion’s left foot. Rigel is the Arabic word for foot. Rigel is much brighter than Betelgeuse because it is much hotter. It’s more than three times as hot as our Sun. However, Rigel is just a baby in size compared to Betelgeuse.

6 . Do you ever get the feeling that you’re being watched? Well, you might be right.

According to a study published in Nature on June 23, astronomers(天文学家) have found that 1,715 stars have had a direct view of Earth since humans were here.

In order to do this, scientists used a method that looked for life on other planets. But instead, they changed the method so it could try to decide what places could see us.

The team looked at 331,312 stars within 326 light-years of Earth. Out of all those stars, only 1,715 of them could see Earth within the last 5,000 years, with an extra 319 stars that will be able to see us in the next 5,000 years.

“When I look up at the sky, it looks a little bit friendlier because it’s like, maybe somebody is waving,” said Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University, US, and the study’s lead writer.

If a planet circling around one of those 1,715 stars is home to advanced life, they could easily see that there is life here because of the oxygen on Earth. If that didn’t give it away, then the radio waves we have sent out into space would also be an indicator. In fact, human-made radio waves have already travelled through 75 of the closest stars on Kaltenegger’s list.

Why haven’t we heard from anyone yet, then?

It takes a long time for messages to travel between star systems. By the time a message could be received, that advanced life would probably not exist anymore.

Alan Boss, a scientist at the Carnegie Institution for Science in the US who wasn’t part of the study, wrote in an email that this long time would limit the chances for different life to exchange “emails and TikTok videos”.

“So we should not expect aliens to show up anytime soon,” Boss said.

The planets and stars are very far away from us. For many years, people have wanted to visit space and the moon. People who go into space are called “astronauts”. The first astronaut went into space about 40 years ago, and some people went to the moon about 8 years later.

Space is amazing. However, it is dangerous in space. Small pieces of rock fly past very quickly all the time. There is no air, so there are no animals or plants. Astronauts have to take air, water and food with them. In space, you can pick up very heavy things easily, but it is difficult to eat and drink. This is very strange for astronauts. For sleeping, astronauts spend the night floating (漂浮) in a sleeping bag.

Besides working, eating and sleeping, what do astronauts spend a lot of time doing in space? It’s exercise. If they don’t take exercise, their bodies start losing bone and muscle(骨骼和肌肉) which makes them weak.

It isn’t good for our bodies to be in space for a long time. Astronauts don’t usually stay in space for very long, but some have stayed for a year without any problems. Perhaps in the future we will all visit the moon or have holidays in space.

On December 25, 2021, a new and exciting age of space science started when the James Webb Space Telescope was launched* into space. According to NASA, Webb is the largest and most powerful space science telescope ever built.

At first, Webb was planned to cost half a billion dollars and launched in 2007. But it turned out to be impossible. As designed, Webb’s orbit* is about 1.6 million kilometers away from the earth. It is too far for the astronauts to repair if it breaks down. So everything has to work perfectly on the first try, and it is the main reason why NASA spent nearly 30 years and 10 billion dollars getting it ready for launch.

Considered as a successor* to the old Hubble Space Telescope, Webb will allow us to look deeper into the universe than ever before. Hubble mostly sees what we see—which is known as visible light. But Webb is designed to focus on the infrared* light, which is invisible to the human eyes. That means Webb can see through dust* in the universe and make new discoveries by examining stars inside those dust clouds. It will try to collect light from the very first stars when the universe was young. By collecting the light, the telescope can see galaxies as they appeared in the past, which could help to explain how the universe began. It will also study the planets around other stars, looking for signs of life.

In order to collect the light and focus it into its camera, the mirror* Webb uses is 6.5 meters across much larger than Hubble’s 2.4-meter-wide mirror. The size advantage gives Webb 6.25 times more surface area to collect light in the universe, letting it see further and more detailed. However, the mirror also needs to be small enough to fit into a rocket to be launched into space. To fit the telescope in the rocket, engineers built the mirror with 18 honeycomb-shaped segments* that could fold up. And during Webb’s journey to the orbit, they will unfold, creating one large mirror.

Now, Webb has been in its orbit for several months, and it will send back its first images in June. By the time, the results will prove it is of great value to put so much time and money in building it.