Level 5 Reading 10A

Reading 10A

读数10A

COSMIC DAWN High in the Andes Mountains, an array of telescopes larger than many cities reveals the secrets of the universe. An Eye on the Heavens Telescopes have come a long way since the first ones were invented early in the 17th century. Traditional telescopes allow astronomers to view objects in space thanks to the visible light those objects emit or reflect. However, for modern telescopes, any electromagnetic radiation will suffice for the purpose of viewing objects in space. Extremely hot objects, such as stars, emit not only visible light but also high-energy gamma radiation. Specialized telescopes—such as NASA's space-based Chandra X-ray Observatory— are built to detect such radiation. Cold objects—like comets and asteroids—emit low-energy radiation, which is invisible to the naked eye. Much of the universe is even colder than this. The clouds of dust and gas of which stars are made are only slightly warmer than absolute zero— the temperature at which atoms stop moving. To capture images of cold objects, astronomers use radio telescopes. A radio telescope is a device that typically uses a large dish antenna to collect the low-energy radiation emitted by objects in space. In the 1960s, astronomers started using them to view asteroids, planets, comets, and other objects. However, it was challenging to get a clear image of those objects using ground-based antennas because low-energy radiation is absorbed and distorted by water vapor in the Earth's atmosphere. The signal that a dish antenna on the ground finally receives is therefore weak. The signal can be strengthened by positioning the antenna on a site with very dry air, and it can be made even stronger by arranging several antennas in an array, combining their signals so that they function together as a single, more powerful

宇宙黎明 在安第斯山脉的高处， 一组比许多城市还大的望远镜揭示了宇宙的秘密。 天空之眼 自17世纪初发明第一台望远镜以来，望远镜已经取得了长足的进步。 传统的望远镜使天文学家能够观察到太空中的物体，这要归功于这些物体发射或反射的可见光。 然而对于现代望远镜来说， 任何电磁辐射都足以用于观察太空中的物体。 恒星等极热物体不仅会发出可见光，还会发出高能伽马辐射。 专业望远镜，如美国国家航空航天局的钱德拉X射线天文台-- 被建造来检测这种辐射。 冷物体，如彗星和小行星，会发出低能量辐射，肉眼看不见。 宇宙的大部分地区甚至比这更冷。 构成恒星的尘埃云和气体云仅比绝对零度略高-- 原子停止运动的温度。 为了捕捉冷物体的图像，天文学家使用射电望远镜。 射电望远镜是一种通常使用大型碟形天线的设备 收集太空中物体发出的低能辐射。 在20世纪60年代，天文学家开始使用它们来观察小行星、行星、彗星和其他物体。 然而，使用地面天线获得这些物体的清晰图像是具有挑战性的 因为低能辐射被地球大气层中的水蒸气吸收和扭曲。 因此，地面上的碟形天线最终接收到的信号很弱。 通过将天线放置在空气非常干燥的地方，可以增强信号， 通过将多个天线排列成阵列，可以使其更加坚固， 将它们的信号组合起来，使它们作为一个更强大的单一信号一起工作

telescope. By the 1980s, several small arrays were operating in Japan, Europe, and the United States. Technological advances soon made much larger arrays possible, provided that a high, flat site could be found where the antennas could be set up. And if the antennas were portable, the distance between them could be adjusted to change the sensitivity of the telescope. Placed far apart, they could zoom in to focus on a small target, such as a planet. Grouping the antennas closer together would have the effect of zooming out, which would be useful for capturing images of an object as large as a galaxy. In the 1990s, astronomers began searching the world for the ideal place to set up a large array of antennas. The Perfect Location One May morning, two small trucks passed through the quiet town of San Pedro in Chile's Atacama Desert and headed up a mountainside. It was 1994, and the men inside the trucks were trying to find the highest, driest, flattest place on Earth. They had already spent a week and a half checking other locations in this desert. Now, guided by a map and a Chilean astronomer named Hernan Quintana, they were searching for the Chajnantor plateau. At 5,000 meters, it is almost as high as the two base camps used by climbers on Mount Everest (Qomolangma). The Atacama Desert is one of the driest places on Earth, with less than 1.2 centimeters of rain a year on average. The desert's remoteness and thin, dry air make the area ideal for observing the night sky. Astronomers from several countries were very interested in setting up observatories there. For the most part, these were observatories to view the fraction of the universe visible using the portion of the light spectrum that the human eye can see. Quintana and his companions were looking for a location to set up an array of dish antennas for a large radio telescope. Quintana felt that the Atacama Desert was likely the best possible place— but it wasn't easy to get to. "The trip was slow and painful, because the tires kept getting stuck in the sand," remembers Riccardo Giovanelli of Cornell University, one of the researchers who accompanied Quintana. When they finally arrived, the group was not disappointed. "The sky was beautiful—it was the deepest blue one can expect to see," remembered Giovanelli. "There was no doubt that somewhere nearby was the place." One of the astronomers brought along an instrument to measure water vapor. It was lower than any other place they had been. News of the discovery inspired a cooperative effort among astronomers in the United States, Europe, and Japan. Scientists in these countries began to realize that by working together, they could build a larger and more powerful array than any one of them could alone. In 1999, an agreement was signed to cooperate on a telescope project. Assembling the Array It would take more than 10 years to transform one of the world's loneliest spots into a busy modern observatory. Land mines planted decades before by the Chilean military had to be located and removed, and an oil company needed to be convinced to choose a different route for a planned pipeline that would have crossed the site. Prototype antennas were redesigned after testing in New Mexico, and new ones needed to be manufactured. The infrastructure for the installation had to be built from scratch, including many kilometers of service roads. The first of the dish antennas—12 meters in diameter and weighing more than a hundred tons— arrived from the United States at the Chilean port of Antofagasta in April 2007. Escorted by police cars, a truck carried the massive dish up the mountain, its progress occasionally interrupted by herds of llamas crossing the road. Over the next five years the dishes continued to arrive. Two specially made 28-wheel transporters—nicknamed Otto and Lore— stood ready to move the antennas to new locations on the plateau as needed. Setting the dishes up to work together required astonishing precision: They would need to turn together on command and point at the same target in the sky within a second and a half of one another. A massive supercomputer had to be installed on-site to coordinate their movements and interpret the signals received. Early Discoveries The installation was officially opened in March 2013 and named the Atacama Large Millimeterf/submillimeter Array, or ALMA for short. Even before it was completely set up, it had already produced results. The year before, with only 16 antennas in operation, researchers led by Caltech's Joaquin Vieira had used ALMA to view 26 distant galaxies. From the images they gathered, they were able to deduce that many stars in those galaxies were a billion years younger than astronomers had previously thought. Since the official opening of ALMA, there has been a steady stream of other discoveries of great interest to astronomers. In July 2013, the telescope's high-resolution images provided clues that may help answer a question that has long puzzled astronomers: Why are massive galaxies so rare in the universe? ALMA is also helping researchers understand how planets are born, by providing the first-ever images of the planet-forming process. One of the ALMA's most notable achievements is the role it played in creating the first image of a black hole. ALMA collaborated with six other observatories to form an array that functions as one Earth-sized telescope. This network collected and processed more than a petabyte of data while staring at a black hole in the distant Messier 87 galaxy. The image—a circular void surrounded by a ring of orange light—made headline news in April 2019. These achievements are just the beginning. In the future, ALMA will show us even finer details of galaxies and star systems. On a dry plateau a few kilometers from where shepherds once slept, our eyes will open upon an unseen universe.

望远镜。到20世纪80年代，日本、欧洲和美国都有几个小型阵列在运行。 技术进步很快使更大的阵列成为可能， 只要能找到一个高而平坦的地方来安装天线。 如果天线是便携式的，可以调整它们之间的距离来改变望远镜的灵敏度。 它们相距甚远，可以放大以聚焦于一个小目标，如行星。 将天线分组得更近将具有缩小的效果， 这将有助于捕获像星系一样大的物体的图像。 20世纪90年代，天文学家开始在世界各地寻找安装大量天线的理想地点。 完美的位置 五月的一个早晨，两辆小卡车驶过安静的圣佩德罗镇 在智利的阿塔卡马沙漠，我们沿着山腰前进。 那是1994年，卡车里的人正试图找到地球上最高、最干燥、最平坦的地方。 他们已经花了一周半的时间检查这片沙漠中的其他地点。 现在，在一张地图和一位名叫赫尔南·金塔纳的智利天文学家的指导下，他们正在寻找查伊南托高原。 海拔5000米，几乎与珠穆朗玛峰登山者使用的两个大本营一样高。 阿塔卡马沙漠是地球上最干旱的地方之一， 平均每年降雨量不到1.2厘米。 沙漠的偏远和稀薄干燥的空气使该地区成为观测夜空的理想场所。 来自几个国家的天文学家对在那里建立天文台非常感兴趣。 在大多数情况下，这些天文台是使用人眼可以看到的光谱部分来观察宇宙可见部分的天文台。 昆塔纳和他的同伴正在寻找一个地点 为大型射电望远镜安装碟形天线阵列。 金塔纳觉得阿塔卡马沙漠可能是最好的地方，但去那里并不容易。 “旅途缓慢而痛苦，因为轮胎一直卡在沙子里。” 康奈尔大学的Riccardo Giovanelli回忆道，他是陪同昆塔纳的研究人员之一。 当他们最终到达时，团队并没有失望。 Giovanelli回忆道：“天空很美，是人们能看到的最深的蓝色。”。 “毫无疑问，附近的某个地方就是那个地方。” 一位天文学家带来了一台测量水蒸气的仪器。 它比他们去过的任何其他地方都低。 这一发现的消息激发了美国、欧洲和日本天文学家之间的合作。 这些国家的科学家开始意识到，通过共同努力， 他们可以构建一个比他们中的任何一个人都更大、更强大的阵列。 1999年，双方签署了一项望远镜项目合作协议。 组装阵列 将世界上最孤独的地方之一改造成一个繁忙的现代天文台需要10多年的时间。 智利军方几十年前埋设的地雷必须被定位和清除， 需要说服石油公司选择不同的路线 计划中的管道将穿过该地点。 原型天线在新墨西哥州测试后重新设计， 需要制造新的。 安装的基础设施必须从头开始建造， 包括数公里的服务道路。 第一个碟形天线——直径12米，重量超过100吨-- 2007年4月，从美国抵达智利安托法加斯塔港。 在警车的护送下，一辆卡车把巨大的盘子抬上山， 它的行进偶尔会被穿过马路的成群美洲驼打断。 在接下来的五年里，这些菜肴不断出现。 两辆特制的28轮运输车，绰号奥托和洛尔-- 随时准备根据需要将天线移动到高原上的新位置。 将盘子放在一起需要惊人的精确度： 他们需要一起听从指挥 并在一秒半的时间内指向天空中的同一目标。 必须在现场安装一台大型超级计算机 以协调它们的运动并解释接收到的信号。 早期发现 该设施于2013年3月正式开放 并命名为阿塔卡马大型毫米波/亚毫米波阵列，简称ALMA。 甚至在它完全建立之前，它就已经产生了结果。 前一年，只有16个天线在运行， 由加州理工学院的Joaquin Vieira领导的研究人员使用ALMA观测了26个遥远的星系。 根据他们收集到的图像，他们能够推断出这些星系中的许多恒星 比天文学家之前认为的年轻10亿年。 自ALMA正式开业以来， 天文学家们感兴趣的其他发现源源不断。 2013年7月，望远镜的高分辨率图像提供了线索 这可能有助于回答一个长期困扰天文学家的问题： 为什么大质量星系在宇宙中如此罕见？ ALMA还帮助研究人员了解行星是如何诞生的， 通过提供行星形成过程的第一批图像。 ALMA最显著的成就之一是它在创建第一张黑洞图像中发挥了作用。 ALMA与其他六个天文台合作，形成了一个阵列，其功能相当于一个地球大小的望远镜。 该网络收集和处理了超过1 PB的数据 同时凝视着遥远的梅西耶87星系中的一个黑洞。 这张照片——一个被橙色光环环绕的圆形空隙——在2019年4月成为头条新闻。 这些成就仅仅是开始。 未来，ALMA将向我们展示星系和恒星系统的更精细细节。 在距离牧羊人曾经睡觉的地方几公里的干燥高原上，我们的眼睛将睁开，看到一个看不见的宇宙。

ALMA'S TEN-MILE-WIDE ZOOM Elevation: 5,000 meters Rearranging antennas on the wide plateau is like adjusting a camera's zoom. When the antennas are far apart, the telescope focuses on tight sections of the sky and fine details. Grouping the antennas closer together is like using a wide-angle lens and takes in wider areas of the sky. ALMA consists of two telescope arrays working together. Two massive transporters relocate antennas in the main array with submillimeter precision. The Morita Array, a separate group of 16 antennas built by Japan, targets large-scale structures in the universe.

阿尔玛的十英里变焦 海拔：5000米 在宽阔的平台上重新排列天线就像调整相机的变焦。 当天线相距甚远时，望远镜会聚焦于天空的狭窄部分和精细细节。 将天线靠得更近就像使用广角镜头一样，可以拍摄到更广阔的天空。 ALMA由两个协同工作的望远镜阵列组成。 两个大型运输机以亚毫米精度重新定位主阵列中的天线。 森田阵列是日本建造的一组由16个天线组成的独立天线，针对宇宙中的大型结构。

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