实用英语听力材料思维导图

This term several useful and interesting courses have been offered. An introduction to European culture, for instance, gives us a lot of background knowledge of the history of European philosophy, literature and arts. From time to time, we see slight shows of famous paintings, and hear tapes of famous pieces of music, these make the lecture all the more interesting.

American society and culture is another course that attracts a large audience. The teacher who visited the united state not long ago, discusses new train and changes in American life, as well as American history and traditions. We like these and other courses very much, because they help us not only to improve our English, but also to broaden our vision.

Most young people enjoy some form of physical activity. It might be walking, cycling, or swimming , or in winter , skating or skiing . It might be a game of some kind —football, hockey, golf or tennis., or it might be mountaineering . Those who have a passion for climbing high and difficult mountains are often looked upon with astonishment. Why are men and women willing to suffer cold and hardship , and to take risks on high mountains ? This astonishment it probably caused by the difference between mountaineering and other forms of activity to which men give their leisure. If we compare mountaineering and other more familiar sports, we might think that one big difference is that mountaineering is not a "team sport". We should be mistaken in this . There are , it is true , no "matcher" between " teams" of climbers , however, when climbers are on a rock face linked by a rope on which their lives may depend , there is obviously teamwork .

If three's a crowd, a new planet recently discovered orbiting a sunlike star is really cluttering up its neighborhood.

The new planet is the fourth Jupiter-like world to be found around the young star HR 8799, astronomers announced today. The same team had previously found the other three planets in 2008, when they took a direct picture of the star system.

Of the more than 500 planets discovered to date outside our solar system, most have been found via indirect methods, such as looking for planets' gravitational tugs on their host stars or for dips in starlight when planets pass in front of their hosts.

The new planet was also found in a direct image of the HR 8799 system. But based on the masses of the planets and their distances from the star, the fourth world challenges current theories of planet formation, according to the study authors.

"This is the first multiplanet system directly imaged so far, so it's quite a feat," said lead study author Christian Marois, an astronomer at the Herzberg Institute of Astrophysics in Canada.

"But we are now stuck with four planets [and] we cannot explain their formation and their current locations by any of our models."

Fourth Planet Too Close to Its Parent?

The previously known planets around HR 8799 are about five, seven, and ten times Jupiter's mass. They orbit between 2.2 billion miles (3.5 billion kilometers) from the star—roughly the same as Neptune's distance from the sun—and 6.3 billion miles (10.1 billion kilometers), or almost twice Pluto's distance.

The most distant planet circles just inside a dusty disk similar to that produced by the solar system's Kuiper belt, a region of small, icy bodies that includes Pluto.

The whole HR 8799 system is estimated to be no more than 60 million years old, so the planets are still glowing with heat from their formation. This heat signature is what betrayed the planets' positions in the previous infrared images of the star.

Astronomers found the fourth planet using the Keck II telescope on the peak of Mauna Kea in Hawaii. The instrument is equipped with a special near-infrared imager and adaptive optics to eliminate the blurring effect of Earth's atmosphere.

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