学校2013

NASA IXPE结果有助于揭开超新星爆炸的秘密_我的网站

一 |     IXPE于2021年12月9日发射，由NASA和意大利航天局合作，是第一个能以这种敏感度和清晰度测量X射线光偏振的卫星。它旨在发现宇宙中一些最极端天体的秘密--超新星爆炸的残余物、由进食黑洞吐出的强大粒子流等。    DEIR AL-BALAH, Gaza Strip -- The only thing worse than the screams of a patient undergoing surgery without enough anesthesia are the terror-stricken faces of those awaiting their turn, a 51-year-old orthopedic surgeon says.When the Israeli bombing intensifies and the wounded swamp the Gaza City hospitals where Dr. Nidal Abed works, he treats patients wherever he can — on the floor, in the corridors, in rooms crammed with 10 patients instead of two. Without enough medical supplies, Abed makes do with whatever he can find – clothes for bandages, vinegar for antiseptic, sewing needles for surgical ones. Hospitals in the Gaza Strip are nearing collapse under the Israeli blockade that cut power and deliveries of food and other necessities to the territory. They lack clean water. They are running out of basic items for easing pain and preventing infections. Fuel for their generators is dwindling.Israel began its bombing campaign after Hamas militants surged across the border on Oct. 7 and killed over 1,400 people, mostly civilians, and abducted more than 200 others. Israel's offensive has devastated neighborhoods, shuttered five hospitals, killed thousands and wounded more people than its remaining health facilities can handle.“We have a shortage of everything, and we are dealing with very complex surgeries,” Abed, who works with Doctors Without Borders, told The Associated Press from Al Quds Hospital. The medical center is still treating hundreds of patients in defiance of an evacuation order the Israeli military gave Friday. Some 10,000 Palestinians displaced by the bombing have also taken refuge in the hospital compound.“These people are all terrified, and so am I," the surgeon said. “But there is no way we'll evacuate.” The first food, water and medicine trickled into Gaza from Egypt on Saturday after being stalled on the border for days. Four trucks in the 20-truck aid convoy were carrying drugs and medical supplies, the World Health Organization said. Aid workers and doctors warned it was not nearly enough to address Gaza’s spiraling humanitarian crisis. “It's a nightmare. If more aid doesn’t come in, I fear we’ll get to the point where going to a hospital will do more harm than good,” Mehdat Abbas, an official in the Hamas-run Health Ministry, said. Across the territory’s hospitals, ingenuity is being put to the test. Abed used household vinegar from the corner store as disinfectant until the stores ran out, he said. Too many doctors had the same idea. Now, he cleans wounds with a mixture of saline and the polluted water that trickles from taps because Israel cut off the water. A shortage of surgical supplies forced some staff to use sewing needles to stitch wounds, which Abed said can damage tissue. A shortage of bandages forced medics to wrap clothes around large burns, which he said can cause infections. A shortage of orthopedic implants forced Abed to use screws that don't fit his patients' bones. There are not enough antibiotics, so he gives single pills rather than multiple courses to patients suffering terrible bacterial infections. “We are doing what we can to stabilize the patients, to control the situation,” he said. “People are dying because of this." When Israel cut fuel to the territory's sole power plant two weeks ago, Gaza's rumbling generators kicked in to keep life-support equipment running in hospitals. Authorities are desperately scrounging up diesel to keep them going. United Nations agencies are distributing their remaining stocks. Motorists are emptying their gas tanks. In some hospitals, the lights have already switched off. At Nasser Hospital in the southern city of Khan Younis this week, nurses and surgical assistants held their iPhones over the operating table, guiding the surgeons with the flashlights as they snipped. At Shifa Hospital, Gaza’s biggest, where Abed also worked this week, the intensive care unit runs on generators but most other wards are without power. Air conditioning is a bygone luxury. Abed catches beads of sweat dripping from his patients’ foreheads as he operates.People wounded in the airstrikes are overwhelming the facilities. Hospitals don't have enough beds for them. “Even a normal hospital with equipment would not be able to deal with what we’re facing,” Abed said. “It would collapse.” Shifa Hospital — with a maximum capacity of 700 people — is treating 5,000 people, general director Mohammed Abu Selmia says. Lines of patients, some in critical condition, snake out of operating rooms. The wounded lie on floors or on gurneys sometimes stained with the blood of previous patients. Doctors operate in crowded corridors filled with moans. The scenes — infants arriving alone to intensive care because no one else in their family survived, patients awake and grimacing in pain during surgeries — have traumatized Abed into numbness. But what still pains him is having to choose which patients to prioritize.“You have to decide," he said. “Because you know that many will not make it."___DeBre reported from Jerusalem.。所有形式的光--从无线电波到伽马射线--都可以被偏振。跟我们用来减少阳光从潮湿的道路或挡风玻璃上反弹的眩光的偏光太阳镜不同，IXPE的探测器绘制了进入的X射线光的轨迹。科学家们可以利用这些单独的轨迹记录来计算出偏振，这就说明了X射线所经历的故事。仙后座A（简称Cas A）是IXPE开始收集数据后观察到的第一个天体。仙后座A被选中的原因之一是它的冲击波--就像喷射器产生的音爆--是银河系中最快的一些。冲击波是由超新星爆炸产生，超新星爆炸摧毁了一颗巨大的恒星后，它坍塌了。

二 | 爆炸产生的光线在三百多年前掠过地球。哈佛大学和史密森学会天体物理学中心的Pat Slane说道：“如果没有IXPE，我们一直在错过有关Cas A这样的天体的关键信息，他领导着IXPE对超新星遗迹的调查。这个结果让我们了解到这个爆炸恒星的碎片的一个基本方面--其磁场的行为。”磁场是不可见的，它对质子和电子等移动的带电粒子进行推拉。在家里，它们负责使磁铁粘在厨房的冰箱上。

三 | 在极端条件下，如一颗爆炸的恒星，磁场可以将这些粒子提升到接近光速。尽管它们的速度超快，但被Cas A中的冲击波卷起的粒子并没有飞离超新星残骸，这是因为它们被冲击波后的磁场所困住。这些粒子被迫绕着磁场线旋转，电子发出一种强烈的光，称为“同步辐射”，它是偏振的。通过研究这种光的偏振，科学家可以在非常小的尺度上“反向设计”Cas A内部发生的事情--这些细节以其他方式很难或不可能观察到。偏振的角度告诉我们这些磁场的方向。如果靠近冲击前沿的磁场非常纠结，那么来自不同磁场方向的区域的混乱的混合辐射将发出较小的偏振量。

四 | 以前用射电望远镜对Cas A的研究表明，射电同步辐射是在几乎整个超新星遗迹的区域产生。天文学家发现，只有少量的无线电波被极化--约5%。他们还确定，磁场的方向是径向的，就像车轮的辐条，从残余物的中心附近向边缘扩散。另一方面，来自NASA钱德拉X射线天文台的数据显示，X射线同步辐射主要来自沿冲击的稀薄区域，靠近残余物的圆形外缘，在那里磁场被预测为与冲击对齐。钱德拉和IXPE使用不同种类的探测器，具有不同的角度分辨率或清晰度。1999年发射的钱德拉的第一张科学图像也是Cas A的。相反，IXPE的数据显示，X射线中的磁场倾向于在径向方向上排列，甚至非常接近冲击前沿。X射线还显示出比无线电观测所显示的偏振量要低，这表明X射线来自于混合了许多不同磁场方向的湍流区。来自阿姆斯特丹大学的Jacco Vink博士是描述Cas A的IXPE结果的论文的第一作者，他说道：“这些IXPE结果跟我们的预期不同，但作为科学家，我们喜欢惊喜。事实上，较小比例的X射线是偏振的，这是Cas A的一个非常有趣的--而且以前没有发现的--特性。”关于Cas A的IXPE结果正在吊起人们的胃口，对目前正在进行的超新星残余物的更多观测。科学家们希望每一个新观测对象都能揭示新的答案--并提出更多的问题--关于这些为宇宙注入关键元素的重要天体。

五 | 意大利国家天体物理研究所/罗马空间天体物理学和行星学研究所的Riccardo Ferrazzoli博士说道：“这项研究体现了IXPE给天体物理学带来的所有新东西。我们不仅首次获得了这些来源的X射线偏振特性的信息，而且我们还知道这些偏振特性在超新星的不同区域是如何变化的。作为IXPE观测活动的第一个目标，Cas A提供了一个天体物理学的‘实验室’来测试团队近年来开发的所有技术和分析工具。”研究论文共同作者、阿姆斯特丹大学的Dmitry Prokhorov表示：“这些结果为将电子加速到令人难以置信的高能量所需的环境提供了一个独特的视角。

六 | 我们只是在这个侦探故事的开始，但到目前为止，IXPE的数据正在为我们提供新的线索来进行追踪。

Current article:http://fuy2s.shaihanhuangwoshang.cyou/list_sob6/fseblz.html

Published on:10:58:46