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'NASA ready to take whatever Universe throws at us'_我的网站

杀害班花逃15年

A | 绍兴两条“宠客公交”游线试运营杭州日报讯近日，绍兴公交全新打造的两条“宠客公交”旅游专线——游1路、游2路启动试运营。 Washington, Oct 12 (UNI) American space agency NASA says its recent attempt to deflect the path of an asteroid was successful, after its Dart probe struck an asteroid head-on.
Scientists have now confirmed the orbit of a 160m-wide space rock known as Dimorphos was altered when the Dart probe struck it head on last month.
Researchers came to the conclusion after making measurements using a range of space and Earth-based telescopes.
The mission was conceived to test a potential strategy to defend the Earth against threatening objects.
Dart's achievement proves such an idea would work, provided it was initiated early enough and the target wasn't overly massive.
"This mission shows that Nasa is trying to be ready for whatever the Universe throws at us," said agency administrator Bill Nelson.
"I believe that Nasa has proven that we are serious as a defender of the planet," he told reporters.
The space agency released a raft of data on Tuesday to support its assessment, including new pictures from the Hubble Space Telescope and from a small Italian spacecraft that stood off from the impact by about 50km (30 miles).
The Double Asteroid Redirection Test (Dart) took place some 11 million km (7 million miles) from Earth.
It saw the refrigerator-sized Nasa satellite drive straight into Dimorphos at 22,000km/h (14,000mph), destroying itself in the process.
The space rock orbits a much larger (780m wide; 2,550ft) object called Didymos. Before impact, the time taken for Dimorphos to make one circuit of its sibling was 11 hours and 55 minutes.
The telescope evidence now indicates this orbital period has been reduced to 11 hours and 23 minutes - a change of 32 minutes. This corresponds to Dimorphos moving closer into to Didymos by "tens of metres".
Nasa had defined a minimum successful period change of Dimorphos of 73 seconds or more. The results released on Tuesday show Dart surpassed this benchmark by more than 25 times.
"This is a 4 percent change in the orbital period of Dimorphos around Didymos. Dart just gave it a small nudge. But if you wanted to do this in the future, you'd want to do it years in advance," commented Nancy Chabot from the Johns Hopkins University Applied Physics Laboratory, which led the mission for Nasa.
"Warning time is really key here in order to enable this sort of asteroid deflection to be used in the future as part of a much larger planetary defence strategy."
Nasa's Dart programme scientist, Tom Statler, also had a word of caution about drawing too many conclusions from the experiment.
Asteroids came in many different guises, he said. Their compositions and constructions were diverse - something that was being emphasised every time a mission visited a new object.
"We should not be too eager to say one test on one asteroid tells us exactly how every other asteroid would behave in a similar situation," he stressed.
"But what we can do is use this test as an anchor point for our physics calculations in our simulations that tell us how different kinds of impacts in different situations should behave."
Four years from now, the European Space Agency (Esa) will have three spacecraft - collectively known as the Hera mission - at Didymos and Dimorphos to make follow-up studies.
UNI ING。

B | 两条线路均从高铁绍兴北站始发，精准对接高铁客流，尤其方便杭州游客乘高铁跨城前往游玩，实现“下车即上车，直达景区门口”，彻底告别“站站停、绕远路”的出行痛点。游1路定位为“禹迹山水线”，全长28公里，设绍兴北站、东湖风景区、大禹陵景区3个站点，串联东湖与大禹陵两大核心景区，湖光山色交融大禹文化，一步一景尽显越地悠远底蕴；游2路则定位为“诗酒书香线”，全长28.5公里，设绍兴北站、黄酒小镇、陆游故里、兰亭风景区4个站点，荟萃酒韵、诗魂、书道三大越地特色文化，堪称古城经典文脉地标的一次性打卡。两条线路均实行3元一票制，双休日及节假日运营，日发班次均为20趟，节假日期间还将根据客流情况动态调整班次。绍兴市公交集团相关负责人表示，此次开通的两条旅游专线，旨在解决游客“站站停、绕远路”的出行痛点，通过精简站点、大站快运的模式，实现从高铁站快速到达景区。