Scientists know quite a lot about stars. After centuries of pointing telescopes at the night sky, astronomers and amateurs alike can figure out key traits of any star, such as its mass or its composition.
To calculate a star’s mass, just look at the time it takes to orbit a companion star. Then do a bit of calculation. To determine what it’s made of, look to the spectrum of light the star sends out. But one question scientists haven’t quite cracked yet is how to calculate the exact time of a star.
“The sun is the only star we know the age of,” says astronomer David Soderblom. He works at the Space Telescope Science Institute in Baltimore, Md. We use what we know about it and how it compares to others, he says, to figure out the age of other stars.
Even well-studied stars surprise scientists every now and then. In 2019, the red supergiant Betelgeuse became gradually dark. At the time, astronomers weren’t sure if this star was just going through a phase. The alternative was more exciting: It might be ready to explode as a supernova. (Turns out it was just a phase.) The sun also shook things up when scientists noticed that it wasn’t behaving like other middle-aged stars. It’s not as magnetically active as other stars of its age and mass. That suggests astronomers still might not fully understand the timeline of middle age.
Using physics and indirect measurements, scientists can make a rough estimate of a star’s age. Some methods, it turns out, work better for different types of stars.
Why do we even care? Galaxies are huge collections of stars of different ages. Star ages might help us figure out how such galaxies grow and evolve or how planets within them form. Knowing star ages might even assist in the search for life in other solar systems.
1. What may scientists want to research about stars most now?| A．Their companions. | B．Their types. |
| C．Their ages. | D．Their characteristics. |
| A．Discussed. | B．Described. | C．Touched. | D．Solved. |
| A．To show scientists still have puzzles about stars. |
| B．To prove scientists have studied stars to the full. |
| C．To provide facts for scientists’ researches on stars. |
| D．To warn scientists to notice some surprising stars. |
| A．The reasons for caring about the space. | B．The significance of researching star ages. |
| C．The ways of measuring a star’s age. | D．The benefits of figuring out solar systems. |
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【推荐1】A new study suggests that dark markings on the planet Mars represent sand — not water. The research in 2015 suggested that lines on some Martian hills were evidence of water. Yet American scientists now say these lines appear more like dry flows of sand. If water is present, it is likely to be a small amount. Water in liquid form would be necessary for microbial (微生物的) life.
NASA, the American space agency, said more research is needed. Michael Meyer is the lead scientist for NASA’s Mars exploration programme. He noted that the latest study does not reject the presence of water. But he admitted, “It just may not be as exciting as the idea of rivers going down the sides of cliffs (悬崖).”
The new findings come from a team led by Colin Dundas of the United States Geological Survey. His team measured 151 of these lines in 10 areas. Most of the lines end with slopes (倾斜) between 28 degrees and 35 degrees. These measurements are similar to active sand dunes (沙丘) on both Mars and Earth. A small covering of dust that moves and sometimes becomes lighter might help explain the markings. They usually appear in the Martian summertime, and then disappear until the next year. If these lines are dry, this suggests that recent Mars bas not had large amounts of liquid water. Dundas and his research team say that many questions remain.
“I still think that Mars has great potential for having had life early on in its history,” Meyer said. “As long as that’s true, we also have a reasonable possibility of life still being on Mars. It just happens to be cryptic or well hidden.”
NASA currently has no robotic — either on Mars or in development — with the ability to climb steep slopes. The lack of such equipment has engineers coming up with ideas like Martian helicopters or planes without pilots.
1. What do American scientists find on Mars now according to their study?| A．A lot of little life. | B．An amount of water. |
| C．Some Martian hills. | D．Dark markings are sand. |
| A．In Martian spring. | B．In Martian summer. |
| C．In Martian autumn. | D．In Martian winter. |
| A．Doubtful. | B．Trustful. | C．Unconcerned | D．Objective. |
| A．Undiscovered. | B．Strange. | C．Magical. | D．Icy. |
【推荐2】Photographer Rebecca Douglas has always been fascinated by the night sky. Her love for stars has taken the U.K. resident on “star walking” trips to Iceland and into the Arctic, where she steps out onto darkened trails to capture twinkling stars and glowing planets in her images.
Hiking at night isn’t uncommon. Plenty of people hike after dark to get to campsites or watch the sunrise from a mountaintop. Star walking goes a step further by blending hiking with stargazing. Rather than heading to an observatory or setting up a telescope in your backyard, star walking takes you on a brief journey to look at the stars from different viewpoints.
Whether you’re in the mountainside or by the lake with stars reflecting on the water, star walking is often much more dynamic than traditional stargazing.
What’s more, star walking is good for you. There are plenty of studies that show the health benefits of being in nature. Spending at least two hours a week outdoors, particularly while engaging in what involves “effortless attention”, can decrease blood pressure, heart rate, and stress levels.
So how does an aspiring star walker get started? It doesn’t take much more than a sturdy pair of boots.
While telescopes and binoculars obviously have their uses, people are encouraged to start with naked-eye stargazing. Using only the eyes allows one to get lost in the infinite expanse of space and lets the mind go.
It is advised that one read up on the night sky before heading out. Free mobile apps, such as Star Walk 2, can help identify celestial bodies（天体）and are easy to use—simply point your phone at the sky to reveal a map. Websites like Sky & Telescope and NASA’s Space Place cover the basics, have in-depth explanations on stars, and offer advice on equipment. Space Place posts monthly skywatching updates, so you can plan outings around events such as meteor showers.
In the United States, national parks are great options for inexperienced night hikers. Many offer guided outings that explain the importance of protecting night skies. Those with a good number of walks under their belt may want to try Glacier National Park in Montana.
If national parks and other dark-sky designated areas are out of range, check local astronomy clubs and observatories for guided sessions. Sites like the International Astronomical Union are useful for finding resources by area.
At the end of the day, the best advice is to take it slow and enjoy the journey.
“With all of the chaos（混乱）that’s happening around us, the one constant has been the night sky,” explains Douglas, who has been exploring popular places nearby, long after the crowds have gone home for the day. “Walking is quite a mindful way of looking up and being reminded that, although everything feels so different, some things are still the same.”
1. According to the passage, star walking refers to ________.| A．going to an observatory |
| B．looking at stars in mountains |
| C．combining hiking and stargazing |
| D．setting up a telescope in the backyard |
| A．it’s easier to identify celestial bodies |
| B．it is good for physical and mental health |
| C．they can enjoy the journey without crowds |
| D．they can raise awareness of protecting night skies |
| A．prepare a pair of strong boots |
| B．start by observing with telescopes |
| C．join an astronomy club or an observatory |
| D．find guided outings with the help of mobile apps |
| A．excite people’s interest in star walking |
| B．recommend some places for star walking |
| C．explain the health benefits of star walking |
| D．introduce the preparations for star walking |
【推荐3】Round and Round They Go
Space is becoming more crowded. On December 3, a Falcon 9 rocket made by SpaceX thundered into the sky. On board were 64 small satellites, more than any American company had launched before in one go.They have a variety of uses, from space-based radar to the monitoring of radio-frequency emissions.
These objects are part of the latest breed of low-Earth-orbit (LEO) satellites. This launch is just a taste of what is planned. SpaceX and OneWeb, a communications firm, plan to launch satellites in their thousands, not hundreds. The pair are set to double the total number of satellites in orbit by2027.
For that to happen,however,three worries must be overcome. Debris (碎片) is the most familiar concern.As long ago as 1978, Donald Kessler,a scientist at NASA, proposed a situation in which, when enough satellites were packed into low-Earth orbits, any collision could cause a chain reaction which would eventually destroy all space craft in its orbital plane (平面).The syndrome which bears Mr. Kessler's name weighs heavily on the minds of executives at the new satellite firms.Debris could cause entire tracts (广阔的一片) of space to be unusable for decades.
Solutions exist. One is to grab malfunctioning satellites and pull them down into-Earth's atmosphere.Another is to monitor space more intensively for debris; a US Air Force programme called Space Fence is due to start in 2019. But technology is only part of the answer. Rules are needed to govern the safe disposal (清除) of old satellites from low-Earth orbit. The United States' Federal Communications Commission is revising its regulations with this in mind. Other countries should follow suit.
Cyber-security is a second, long-standing worry. Hackers could take control of a satellite and seal intellectual property, redirect data flows or cause a collision. The satellite industry has been slow to respond to such concerns. But as more of the world's population comes to rely on the infrastructure of space for access to the internet, the need for action intensifies.
The third issue follows from the first two. If a simple mistake or a cyber-attack can cause a chain reaction which wipes out hundreds of billions of dollars of investment, who is liable?Underwriters (保险商) are studying the plans of firms that wish to operate large numbers of satellites.But there is a long way to go before the risks are well understood,let alone priced.
As space becomes more commercialized, mind-bending prospects open up: packages moved across the planet in minutes by rocket rather than by plane, equipment sent to other small planets, passengers launched into orbit and beyond. All that and more may come,one day. But such activities would raise the same questions as LEO satellites do. They must be answered before the space economy can truly develop.
1. What can we learn about LEO satellites from the passage?| A．They are supposed to limit the space economy. |
| B．They are expected to increase in large numbers. |
| C．They are designed to move beyond the Earth as far as possible. |
| D．They are mainly intended to bring internet connectivity to remote areas. |
| A．depending entirely on the modern technology |
| B．monitoring the movement of spaceships carefully |
| C．strengthening rules to remove old satellites safely |
| D．destroying all the satellites with problems instantly |
| A．Measure. |
| B．Increase. |
| C．Spread. |
| D．Repeat. |
| A．Lack of satellite regulations. |
| B．Loss of intellectual property. |
| C．Crisis of confidence in the field. |
| D．Slow response of satellite industry. |
| A．It should be further confirmed for it ownership. |
| B．It should be continued because of its advantages. |
| C．It should be done carefully to avoid potential risks. |
| D．It should be stopped in face of the space economy. |
【推荐1】By now it's almost common knowledge that spending time in nature is good for you. Areas with more trees tend to be less polluted, so spending time there allows you to breathe easier. Spending time outdoors has been linked with reduced blood pressure and stress and seems to motivate people to exercise more.
“So it'll come as surprise that there's research showing that spending time in nature is good. There are dozens of papers showing that,” University of Exeter Medical School researcher Mathew P.White said.“We get this idea-patients are coning to us and they are asking, ‘Doctor, how long should I spend? ’And the doctor is saying,‘I don't really know.’”
So White and his team decided to find out by using data collected from nearly 20,000 people in England through the Monitor of Engagement with the Natural Environment Survey. And their answer? Two hours a week. People who spent at least that much time in nature either all at once or totaled over several shorter visits were more likely to report good health and psychological well-being than those with no nature exposure.
Remarkably, the two-hour standard applied to men and women, to older and younger folks, to people from different ethnic backgrounds, occupational groups, socioeconomic levels, and so on. Even people with long-term illnesses or disabilities benefited from time spent in nature- as long as it was at least 120 minutes per week.
While the findings are based on a vast number of people, White cautions that it's rally just a correlation. Nobody knows why of how nature has this benefit, or even if the findings will stand up to more strict investigation.
“I want to be rally clear about this. This is in very early stages.We're not saying everybody has to do 120. This is really to start the conversation, saying, what would athresholdlook like? What research do we need to take this to the next step before doctors can have the true confidence to work with their patients? But it's certainly a starting point.”
1. What does White want to figure out in the survey?| A．The benefits of being outside. |
| B．How long we should stay in nature. |
| C．The significance of outdoor activities. |
| D．Whether the British spend enough time in nature |
| A．The two-hour standard applies to everyone. |
| B．The reason why nature is beneficial is clear. |
| C．Further study is needed to confirm White's result. |
| D．The findings of White's survey have bee widely used. |
| A．Strict investigation. | B．Following step. |
| C．Healthy lifestyle. | D．Staring point. |
| A．Nature and Health | B．Two-hour Staying in Nature |
| C．Tips to Improve Health | D．The Starting Point |
【推荐2】Driving in Canada is similar to driving in many parts of the United States. Distances and speeds, however, are posted in kilometers per hour and some signs, particularly in Quebec, may only be in French.
Unless otherwise posted, the maximum speed limit in Canada is 50km/hr in cities and 80km/hr on highways. On rural highways, the posted speed limit may be 100km/hr. It is illegal to take automobile radar detectors into Quebec, Ontario, Manitoba, and the Yukon. Seat belt use is required by law for all passengers, and child car seats must be used by children under 40 pounds. Some provinces require drivers to keep their vehicles’ headlights on during the day and some have banned driving while using a hand-held cell phone. Motorcycles cannot share a lane, and safety helmets for motorcycle riders and passengers are necessary. Running a red light is a serious crime throughout Canada and drivers are advised to stop before starting when a light turns green.
Winter travel can be dangerous due to heavy snowfalls and icy conditions. Some roads and bridges are often closed in winter. Snow tires are required in some provinces. Travelers should also be careful about animals while driving at night in rural areas.
Highway 401, from Detroit to Montreal, is one of the busiest highways in North America. It has been the scene of many deadly traffic accidents due to sudden and severe weather changes, high rates of speed, and heavy truck traffic. Thus drivers should be alert while travelling here.
Please refer to our Road Safety page for more information. Also, we suggest that you visit the website of Canada’s national authority responsible for road safety.
1. Which of the following is TRUE according to the text?| A．All signs on the roads in Quebec are in English. |
| B．Automobile radar detectors are allowed to be used in Manitoba. |
| C．Passengers may choose not to wear seat belts while in a car in Canada. |
| D．The speed of cars in Canadian cities should be less than 50km/hr. |
| A．careful | B．relaxed | C．nervous | D．pleased |
| A．Different traffic rules in Canada | B．Tips for traveling by car in Canada |
| C．Special rules for driving in Canada | D．Traffic safety and road conditions in Canada |
【推荐3】Throughout history, people have been interested in knowing how languages first began, but no one knows exactly where or how this happened. However, we do know a lot about languages, the languages of today and also the languages of earlier times. There are probably about 3,000 languages in the world today. Chinese is the language with the most speakers. English, Russian and Spanish are also spoken by many millions of people. On the other hand, some languages in the world have less than one hundred speakers.
There are several important families of languages in the world. For example, most of the languages of Europe are in one large family called Indo-European. The original (最初的) language of this family was spoken about 4,500 years ago. Many of the present day languages of Europe and India are modern forms of the language of 4,500 years ago.
Languages are always changing. The English of today is very different from the English of 500 years ago. In time some even died out completely. About 1,000 years ago, English was a little-known relative of German spoken on one of the borders of Europe.
If a language has a large number of speakers or if it is very old, there may be differences in the way it is spoken in different areas. That is, the language may have several dialects. Chinese is a good example of dialect differences. Chinese has been spoken for thousands of years by many millions of speakers. The differences between the dialects of Chinese are so great that speakers of Chinese from some parts of China can’t understand speakers from other parts.
1. The first paragraph mainly tells us that ____ .| A．most people in the world speak Chinese |
| B．there are thousands of languages in the world today |
| C．man has much knowledge about languages |
| D．some people know several languages |
| A．will soon die out completely | B．were once a relative of English |
| C．are no longer spoken | D．come from the same family |
| A．Chinese | B．English | C．Spanish | D．German |
| A．German | B．English | C．Spanish | D．Chinese |
| A．a special language spoken by Chinese |
| B．the sign used by the Chinese people in a special area |
| C．the difference between the old and today’s Chinese |
| D．the form of a language used in one part of the country |
