On 15 October 1997, the Cassini spacecraft set out on a mission to explore the planet Saturn. So great was the distance from Earth that it     1    (would / shall) need to travel for almost six years to reach its destination. When it reached Saturn, it sent back amazing images of the planet's famous rings viewed in ultraviolet light. Cassini made numerous trips around Saturn so it     2    (could / must) collect data. Over the following years, Cassini took some 450, 000 images of the planet and its moons. Finally, on 15 September 2017, Cassini was pointed towards Saturn so that it     3    (should / would) meet a fiery end. Scientists had decided that Cassini     4    (could / must) be destroyed this way, so it     5    (must / would) not collide with any of Saturn's moons. In its nearly 20-year mission, Cassini provided so much information that scientists     6    (could / would) not process it all. No wonder so many people took to social media to bid it goodbye, saying, “Farewell, dear Cassini! We     7    (shall / should) never forget you!”

The U.S. space as agency NASA has released the first images captured by the James Webb Space Telescope, the most     1     (powerful) equipped telescope ever put into space. The Webb launched in December, 2021     2     a mission     3     (see) farther into space and farther back in time than ever before and observe faraway planets for signs of life.

One of the images shows some of the first galaxies (星系) ever to form, which means the Webb is seeing the galaxies that existed about 13 billion years ago. Additional     4     (photo) taken by the Webb show a cloud of gas and dust     5     stars are born, a distant planet’s atmosphere, and a dying star. This is just the beginning of     6     (it) mission, which     7     (expect) to last at least 5 to 10 years.

The Webb is the result of a $10 billion, 25-year project led by NASA and supported by other space agencies.     8     (name) after former NASA head James Webb, the telescope is about 100 times better than NASA’s Hubble Space Telescope, which is still operating after more than 30 years. The Webb collects and     9     (analyze) infrared light, using 18 mirrors covered in a thin layer of gold. The Webb also has a sun shield     10     size of a tennis court to help keep it cool.

4 . Scientists for the first time have found water in the atmosphere of an Earth-like planet orbiting a distant star. It is the evidence that a key ingredient for life exists beyond our solar system, according to a study published in 2019.

Water vapor was found in the atmosphere of K2-18b, one of the hundreds of “super-Earths” recorded in a new field of astronomy that explores the so-called exoplanets, which are planets that orbit a star other than the sun. In total, more than 4,000 exoplanets of all types and sizes have been found.

The latest discovery was reported in research by a team of scientists at University College London (UCL) published in the journal Nature Astronomy. “We found water through the Hubble Space Telescope,” UCL astrophysicist Ingo Waldmann said. It marks the first time that scientists have found water in the atmosphere around a super-Earth.

Angelos Tsiaras, an astronomer at UCL, said the team is working on finding exoplanets whose conditions are similar to those on Earth. “But of course its purpose is not to find a place where we could go,” Tsiaras said. “While light from the sun takes several minutes to reach Earth, light from K2-18b’s star takes a century to reach our planet, so it’s impossible for us to travel there.”

“Considering it’s so far away, we don’t really have any other choice but to stay on our own Earth, so it’s important to make Earth great again rather than looking for another planet to take the place of Earth,” Tsiaras said.

Besides the quite long distance separating Earth from K2-18b, there is far more radiation on the exoplanet than on Earth, which diminishes the possibility for life to exist. However, the discovery brings astronomers closer to answering the fundamental question of how special Earth is in the universe, the scientists said.

The probe of China’s first Mars mission Tianwen-1 flew a total of 100 million kilometres by 10:08 a.m.    1     Friday,according to China National Space Administration.

    2     (launch) on July 23,the probe was sent into the Earth-Mars transfer trajectory(轨道) by the country’s Long March-5 carrier rocket.It becomes     3     artificial planet to circle the Sun together with the Earth and the Moon,    4     (fly) away from the Earth and approaching the red planet.It is now 10.75 million kilometres away from the Earth     5     36 days’ travel.When arriving at Mars,the probe will be about 195 million kilometres from the Earth with an actual flight     6     (distant) of roughly 470 million kilometres.

During the flight,the probe has     7     (successful) captured a photo of the Earth and the Moon,and completed the first mid-course orbital correction.

It is expected     8     (carry) out deep-space maneuvers and multiple mid-course corrections later,and conduct orbiting,landing and roving missions after approaching the Mars orbit.

The Tianwen-1     9     (schedule) to make a second orbital correction in September to ensure that the probe is flying accurately in     10     (it) preset orbit.

8 . Here's a list of some interesting facts about stars; some you might already know, and few that are going to be new.

The sun is the closest star to the earth. The sun is about 150 million kilometers away. Our sun, like most other stars, gives off power and light by nuclear fusion, which happens exactly where it's the hottest. The sun is about 4.5 billion years old and it will still last six billion years or so. When it runs out of its fuel, it would develop into a red star when increasing in size.

Since stars are billions of light years away, it may be hard to recognize that stars are in continuous battles with themselves. All the stars have their own gravitational pull that pulls them. The surprising part is that the nuclear fusion occurring inside the star truly produces an outward push to resist the gravitational force, which keeps its present shape.

Stars have different colors. The hottest stars are surprisingly the smallest ones and are blue in color. Their temperatures go to about 12,000 Kelvin. Although the yellow-colored stars are the middle-sized ones just like the sun, their temperatures fall to about 6,000 Kelvin. And lastly, the coolest and greatest ones are colored red and the temperatures of them are about 3,000 Kelvin.

When looking at the night sky, we may think that stars are up there alone. But don't be surprised that these heavenly bodies in fact come in pairs. And stars can even come in groups of 3 or even 4!

10 . Some new comets have been discovered accidentally by amateur (业余的) astronomers. Surprisingly a few bright comets have been discovered with the naked eye (肉眼) by members of the general public. However, a great number of comets are found by comet hunters carrying out telescope searches of chosen areas of the night sky.

As the movement of all comets is directed around the Sun and because these bodies brighten as they move towards the Sun, there is a greater possibility for the discovery of a new comet in the skies towards the Sun rather than away from the Sun's direction. This means that searches should be put on the western sky after evening light and on the eastern sky before morning light.

From the astronomical point there is no time during the year which is the best for the discovery of new comets. A search can be done at any time providing there is no bright Moon.

Studies done on the discovery conditions of comets discovered before show that more comets have been discovered in the morning sky than in the evening sky. Thus the smart comet hunter should make sure that morning activity receives as much if not more attention than any evening effort.

In recent times, the use of advanced CCD technology to discover objects close to the Earth will in the future greatly reduce the chances of new comets being found with small telescopes. An example of the new technology is the very successful LINEAR program operating in New Mexico, However, until a similar system is based in the southern half of the Earth there will continue to be chances for the discovery of new comets which come from the south.