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China adds Kyrgyzstan, Vietnam to 240-hour visa-free transit program, raising total covered countries to 57._我的网站

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一 | (ECNS) -- China has expanded its 240-hour visa-free transit policy to citizens of Kyrgyzstan and Vietnam, bringing the number of countries covered by the policy to 57, according to the National Immigration Administration (NIA) on Wednesday. Under the new arrangement, which took effect on Aug. 20, citizens of Kyrgyzstan and Vietnam holding ordinary passports and interline passenger tickets with confirmed dates and itineraries bound for a third country or region may enter China through any of the 65 ports across the country and stay up to 240 hours, or 10 days, without a visa, according to the National Immigration Administration (NIA). Citizens of these two countries who hold ordinary passports will also be eligible for the 30-day visa-free entry policy for Hainan Province in south China starting the same day. This will allow them to enter the province through Hainan's open ports and stay visa-free for up to 30 days. With these additions, the number of countries covered by this Hainan visa-free policy has now reached 61. During the visa-free period, travelers are permitted to engage in tourism, business, exchange visits and family visits. However, the two policies do not cover employment, study or journalistic activities, which still require appropriate visas, the NIA said. An NIA official said the measures are part of efforts to advance high-level opening-up and facilitate exchanges and cooperation with neighboring countries. Looking forward, the NIA will continue to support international travel while ensuring orderly border management. (By Intern Liu Shuagjing, Zhang Dongfang) 。这张图像展示了已知最大星系IC1101。

二 | 图片来源：NASA/ESA/哈勃太空望远镜　　据ScienceNews网站最新报道，包括西班牙天文学家在内的联合团队通过超深成像观测确认已知最大星系边界。

三 | 这个名为IC1101的星系直径达到约520千秒差距（星系尺度单位），接近170万光年，宽度相当于17个银河系并排排列，而这个星系目前还在成长。

四 | 　　确定这一尺度的关键，是天文学家获取了迄今对IC1101曝光时间最长、探测最深的影像。这些图像由位于西班牙加那利群岛拉帕尔马岛的艾萨克·牛顿望远镜于早前拍摄。经过最新详细测算，天文学家得以识别这颗巨星系暗淡的外缘，同时算出IC1101的恒星物质总质量约为3.4万亿个太阳质量。　　IC1101坐落在距地球超过10亿光年的Abell2029星系团中心，是该星系团中光度最高的星系。这类星系位居宇宙中最庞大星系之列，其成长方式是通过反复吞并附近较小的星系来不断扩张，这一过程被称作星系同类相食。

五 | 　　此前的研究已经暗示IC1101体量巨大，但始终未能精确界定星系本体与外围星系团弥散物质之间的过渡边界。本次超深观测填补了这一空白。加那利天体物理研究所的天文学家们在星系边缘识别出带状尾流结构，认为这是IC1101与其他星系发生并合的产物，表明该星系迄今仍在吸积物质，生长并未停止。　　加那利天体物理研究所天文学家卡洛斯·马雷罗-德拉罗萨表示，IC1101展示了涉及反复并合与吸积的星系演化过程在极端尺度上的样貌，是可参照的星系未来演变样本。　　这次边界判定之所以重要，是因为最亮团星系的暗弱外围通常会混入星系团的弥漫星光，导致很难判断巨星系本体的终结位置。IC1101的测量结果为这类天体的尺度研究提供了方法论样本。作为已知最大的星系，它的存在也揭示了在数十亿年的时间尺度上，宇宙中的最大尺度星系结构可以通过持续吞并周围星系而发展到何等极端的规模。