4 . Have you ever got the thought or feeling that you’re being watched? Well, guess what? You might be right.

According to a study published in Nature on June 23, astronomers have found that 1,715 stars have had a direct view of Earth since humans have been here.

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

The team looked at 331,312 stars within 326 light-years of Earth, with each light-year equaling 9.4 trillion kilometers. 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 (研究所) 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 (标志). In fact, human-made radio waves have already traveled 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 civilization (文明) 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.

6 . Mounting a telescope on the balcony at home, Wang Zhipu, a 16-year-old boy from Fujian Province, observes the skies, takes photos and begins his voyage into space after class. Recently, his efforts were rewarded when he won the title of “Young Astronomy Photographer of the Year 2021” in the Royal Observatory Greenwich’s annual astrophotography contest. His winning entry, entitled Family Photo of the Solar System, shows seven of the eight planets lined up horizontally, with the sun on the left and moon on the right, both pictured larger in size than normal.

“All families are unconventional, so I adored this fresh, gently playful concept around the solar system,” said the competition judge Sue Prichard while talking about Wang’s picture. “A meaningful technically accomplished work from a rising star of astronomical photography.”

It hasn’t been easy taking pictures of outer space. For about half a year, Wang had to calculate the best time to shoot planets when they’re opposite the sun in Earth’s sky to get the brightest images. What’s more, he still needed to wait for clear weather to see better. For example, to capture a clear picture of Mercury, the planet closest to the sun, which is often cited as the most difficult of the five brightest planets to see with the naked eye, Wang tried to shoot it three times in the early morning but failed. At sunset, he shot 10, 000 frames of video and selected several thousand better frames to overlay, further refine them and form a more satisfactory picture.

Sometimes Wang would be so absorbed in his observations that he wouldn’t go downstairs to fetch a coat, even in the middle of winter. Other times, he stood for hours under the burning sun to get the perfect shot. To get an ideal shot, he often gets up at dawn, sleeps early to wake up at midnight, and even takes time off from evening classes when necessary.

8 . China's Mars rover, Tianwen-1, will likely attempt to land at a site in northeastern Mars, according to a new paper published just days ahead of the mission's launch. The paper was written by team members of China's Tianwen-1 Mars mission, which aims to send an orbiter and a rover to the Red Planet.

The study reveals new details about Tianwen-1, outlining its intended landing area, science goals and the names of instruments aboard the spacecraft. It also stresses the historic nature of the mission: Not only is Tianwen-1 China's first fully homegrown Mars mission, it's also the first to carry both an orbiter and a rover.

Tianwen-1 means "questions to heaven“ and was taken from the title of a poem by Qu Yuan (340 — 278 BC). The spacecraft will reach Mars in February 2021, at the same time as NASA's Perseverance rover and the United Arab Emirates5 Hope orbiter launched on Sunday (July 19). However, China's rover will remain attached to the orbiter for two to three months before attempting its landing, according to the paper.

The chosen landing area is Utopia Planitia, a huge basin formed by a large impact far back in Mars' history that was also the region where NASA's Viking 2 lander touched down in 1976. China had isolated a part of the vast plain as a landing area, which means there will be more time and atmosphere for the entry spacecraft to slow down and safely land on the surface. The latitude is also suitable for receiving enough sunlight to power the 240 kilograms rover. The relatively smooth surface will also be helpful for roving. The mission also benefits from the engineering heritage of China's Chang'e lunar exploration program, the paper noted.

The Tianwen-1 orbiter will operate in a polar orbit in order to map Mars. The rover will also investigate the surface soil characteristics and water-ice distribution with its own Subsurface Exploration Radar. It will also analyze surface material composition and characteristics of the Martian climate and environment on the surface.