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South Africa hopes to ease crippling blackouts as major power station recovers_我的网站
A | 这一意外的发现提出了关于这些异域大气可能是什么样的问题。这一发现是利用欧洲南方天文台的超大型望远镜(ESO's VLT)得到。 JOHANNESBURG -- South African officials are hoping that the gradual recovery of one of the country's biggest coal-fired power stations will reduce crippling power blackouts.At least two units at the Kusile power station have been restored in the last three weeks, adding 1,600 megawatts to the national grid and reducing the rolling power blackouts, which can last up to 12 hours a day.The units have been out of service since they broke down in October last year, contributing significantly to the blackouts, known in South Africa as loadshedding.The two units were restored nearly two months ahead of schedule and two more are expected to be brought back online before the end of the year, officials said.While the full recovery of the power station is unlikely to end all power blackouts, it is seen as a significant step toward resolving the power crisis that has severely affected households and the country’s economy.The Kusile power station has six generating units capable of producing 800 megawatts each, making it one of the biggest coal-fired power stations in the world with a total capacity of 4,800 megawatts of electricity.“Both units are adding 1,600 megawatts back into the grid, thereby improving the available generation capacity. This signifies that Eskom is on the right path to reducing and ultimately ending loadshedding,” Daphne Mokwena, spokesperson for power utility Eskom, said Tuesday.The government remains under pressure to bring Kusile and another power station, Medupi, up to full operation. Construction delays, cost overruns and allegations of corruption have besieged both power stations since their construction began in 2007.South Africa has committed to a transition from a heavy reliance on coal for electricity generation to cleaner sources including solar, wind and battery storage. The transition has secured funding pledges of up to $8.5 billion from France, the U.K, Germany, the U.S. and the European Union.However, the country's electricity crisis has led the government to consider prolonging the lifespan of its aging power stations.The country has also launched a program to secure additional electricity from neighboring countries.。来自波尔图大学和葡萄牙天体物理研究所(IA)的博士生Tomás Azevedo Silva表示：“令人费解和反直觉的部分是：为什么在这些行星的大气层上层会有如此重的元素？”Silva领导了这项研究，该研究于10月13日发表在《Astronomy & Astrophysics》上。WASP-76 b和WASP-121 b不是普通的系外行星。这两颗行星都被称为超热木星，因为它们的大小跟木星相当，同时具有极高的表面温度，可以飙升到1000℃以上。
B | 这是由于它们非常接近它们的主星，这也意味着围绕每颗恒星的轨道只需要一到两天的时间。这使这些行星具有相当奇特的特征。比如，天文学家怀疑WASP-76 b上会下铁雨。但即便如此，天文学家们还是惊讶地发现，在WASP-76 b和WASP-121 b的高层大气中发现了比铁重1.5倍的钡。
C | “鉴于这些行星的高重力，我们预计像钡这样的重元素会迅速落入大气层的下层，”研究论文共同作者Olivier Demangeon指出。他也是来自波尔图大学和IA的研究人员。Azevedo Silva说道：“这在某种程度上是一个‘意外’的发现。我们并没有特别期待或寻找钡，并且必须交叉检查这是否真的来自该行星，因为之前从未在任何系外行星上看到过。”在这两颗超热木星的大气中检测到钡的事实表明，这类行星可能比以前认为的还要奇怪。尽管我们在自己的天空中确实偶尔会看到钡，就像烟花中绚丽的绿色一样，但科学家们的问题是什么自然过程会导致这种重元素在这些系外行星中处于如此高的高度。
D | “目前我们不确定机制是什么，”Demangeon说道。在研究系外行星的大气层时，超高温的木星是非常有用的。正如Demangeon解释的那样--“由于是气态并呈现高温，它们的大气层非常宽广，因此比那些较小或较冷的行星更容易观察和研究。”确定一颗系外行星大气层的组成需要非常专业的设备。研究小组利用智利欧空局VLT上的ESPRESSO仪器来分析经过WASP-76 b和WASP-121 b大气层过滤的星光，这使得他们有可能清楚地探测到其中的几种元素，包括钡。这些新结果表明，我们人类只是触及了系外行星之谜的表面。有了未来的仪器如高分辨率的ArmazoNes高色散埃切莱特光谱仪(ANDES)，它将在ESO即将到来的极大型望远镜(ELT)上运行，天文学家将能够更深入地研究大大小小的系外行星的大气--包括跟地球相似的岩质行星的大气--以及收集关于这些陌生世界的性质的更多线索。
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