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一 |     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。    AI摘要      受强降雨影响，台湾南部多地停班停课，部分区域积水严重。气象部门发布豪雨特报，预计降雨持续至25日，并密切关注第18号台风“沙德尔”动向。         台北8月23日电（记者 马欣然、黄扬）受低压带及偏强西南风双重影响，台湾近日持续降雨，南部雨势尤为明显。台南、高雄、屏东宣布23日停班停课，部分地区累计雨量接近300毫米。    台经济事务主管部门的“水利署”23日7时发布最新淹水警戒，高雄市与台南市多地拉响警报。    据悉，屏东县万丹乡22日晚累计雨量达299毫米，高雄部分地区也出现明显降雨。台南地区自当日深夜起降雨几乎未停，部分路段积水一度超过成人膝盖高度，有公路入口临时封闭。目前，台南市对部分积淹水较严重路段实施交通管制，抽水站及移动式抽水机组持续运转。    当地居民也加强防范。有台南市民说，22日晚曾遭遇积水，看到雨势再起便提前准备沙包，有人凌晨守在家门口，“担心水再度淹进家中”，部分车辆因来不及驶离积水路段故障。    目前，台湾南部雨势仍未完全缓解，相关部门持续监测降雨及各地灾情。

二 | 台气象部门23日持续发布豪雨特报，并预估此轮降雨至少持续至25日清晨，嘉义以南仍是防范强降雨的重点区域。    关于第18号台风“沙德尔”，台气象部门表示，台风后续路径仍存在不确定性，将持续观察其对台湾天气的影响。

三 | 台湾气象专家吴德荣推测，“沙德尔”有可能成为今年首个登陆台湾的台风。

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