For the first time, astronomers have directly measured the speed of superheated gas billowing from a cauldron of stellar activity at the heart of M82, a nearby galaxy undergoing an extraordinary burst of star formation.
天文学家首次直接测量了 M82 中心恒星活动大锅中滚滚过热气体的速度，M82 是附近的一个星系，正在经历一场非凡的恒星形成爆发。
The material is moving more than 2 million miles (over 3 million kilometers) per hour and appears to be the primary force driving a cooler, well-studied, galaxy-scale wind.
这种物质每小时移动超过 200 万英里（超过 300 万公里），似乎是驱动更凉爽、经过充分研究的星系级风的主要力量。
Researchers made the calculations using data from the Resolve instrument aboard the XRISM (X-ray Imaging and Spectroscopy Mission) spacecraft.
研究人员利用 XRISM（X 射线成像和光谱任务）航天器上的 Resolve 仪器的数据进行了计算。
“The classic model of starburst galaxies like M82 suggests that shock waves from star formation and supernovae near the center heat gas, kick-starting a powerful wind,” said Erin Boettcher, an astrophysicist at the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Prior to XRISM, though, we didn’t have the ability to measure the velocities needed to test that hypothesis. Now we see the gas moving even faster than some models predict, more than enough to drive the wind all the way to the edge of the galaxy.”
马里兰大学帕克分校和位于马里兰州格林贝尔特的美国宇航局戈达德太空飞行中心的天体物理学家艾琳·博彻 (Erin Boettcher) 表示：“像 M82 这样的星暴星系的经典模型表明，中心附近的恒星形成和超新星产生的冲击波会加热气体，从而引发强大的风。” “不过，在 XRISM 出现之前，我们没有能力测量检验这一假设所需的速度。现在我们看到气体的移动速度甚至比某些模型预测的还要快，足以将风一路吹到星系边缘。”
A paper about the result, led by Boettcher, published Wednesday, March 25, in Nature. The XRISM mission is led by JAXA (Japan Aerospace Exploration Agency) in collaboration with NASA, along with contributions from ESA (European Space Agency) . NASA and JAXA also codeveloped the Resolve instrument.
由 Boettcher 领导的一篇关于该结果的论文于 3 月 25 日星期三发表在《自然》杂志上。 XRISM 任务由 JAXA（日本宇宙航空研究开发机构）与 NASA 合作领导，ESA（欧洲航天局）也做出了贡献。 NASA 和 JAXA 还共同开发了 Resolve 仪器。
Sometimes called the Cigar galaxy , M82 is located 12 million light-years away in the northern constellation Ursa Major. Astronomers classify it as a starburst galaxy because it’s forming stars at a much higher rate than typical for its size — about 10 times faster than the Milky Way .
M82 有时被称为雪茄星系，位于北方大熊座，距离我们 1200 万光年。天文学家将其归类为星爆星系，因为它形成恒星的速度比其大小的典型速度要快得多，大约比银河系快 10 倍。
M82 is well known for its extended, cool wind, which stretches out to 40,000 light-years and propels huge quantities of gas and dust. Scientists have studied it with many missions, including NASA’s Chandra , Webb , Hubble , and retired Spitzer space telescopes, trying to connect the dots between the stellar activity and the large-scale outflow.
M82 以其绵长、凉爽的风而闻名，风的范围可达 40,000 光年，并推动大量的气体和尘埃。科学家们通过许多任务对它进行了研究，包括美国宇航局的钱德拉、韦伯、哈勃和退役的斯皮策太空望远镜，试图将恒星活动和大规模外流之间的点联系起来。
Researchers particularly want to understand the role of cosmic rays . These high-speed charged particles are found throughout the cosmos and are accelerated by some of the same events scientists think produce winds like in M82. There’s a possibility they are a main source of outward pressure on the gas.
研究人员特别想了解宇宙射线的作用。这些高速带电粒子在宇宙中随处可见，科学家认为这些高速带电粒子会因一些与 M82 中产生风的事件相同的事件而加速。它们有可能是气体向外压力的主要来源。
The XRISM Resolve instrument’s high resolution and sensitivity allowed Boettcher and her colleagues to accurately measure the speed of the hot wind by looking at an X-ray signal from superheated iron in the galactic center.
XRISM Resolve 仪器的高分辨率和灵敏度使 Boettcher 和她的同事能够通过观察银河系中心过热铁的 X 射线信号来准确测量热风的速度。
The amount of X-ray light from iron and other elements told them the temperature — right within predictions at 45 million degrees Fahrenheit (25 million degrees Celsius). The heat exerts pressure on the gas and pushes it outward. This rushing from high pressure to low pressure forms the wind — the same reason winds blow through Earth’s atmosphere.
来自铁和其他元素的 X 射线量告诉他们温度——正好在 4500 万华氏度（2500 万摄氏度）的预测范围内。热量对气体施加压力并将其向外推出。这种从高压流向低压的过程形成了风——这与风吹过地球大气层的原因相同。
The broadness of iron spectral lines conveyed the hot wind’s speed. This works through Doppler shifting, the same phenomenon that causes the pitch of a sound, like a siren, to rise or fall due to the source’s motion toward or away from you. In the case of M82, the hot material near the center flies quickly in both directions, stretching out the iron’s spectral line. The amount of stretching reveals the iron’s velocity. The researchers found that the wind is a little faster than expected. Combined with the high temperature, it’s powerful enough to produce the cool wind without cosmic rays, although they may still be contributing.
铁谱线的宽度传达了热风的速度。这是通过多普勒频移来实现的，这种现象会导致声音（如警报器）的音调因声源朝向或远离您的运动而上升或下降。就 M82 而言，中心附近的热物质快速向两个方向飞行，拉长了铁的谱线。拉伸量揭示了铁杆的速度。研究人员发现风速比预期的要快一些。再加上高温，它的威力足以产生凉爽的风，而无需宇宙射线，尽管它们可能仍在发挥作用。
The researchers calculate that the center of M82 expels enough gas every year to form seven stars with the mass of our Sun. This presents another puzzle.
研究人员计算出，M82 中心每年排出的气体足以形成七颗质量相当于太阳的恒星。这又提出了另一个难题。
“If the wind blows steadily at the speed we’ve measured, then we think it can power the larger, cooler wind by driving out four solar masses of gas a year. But XRISM tells us much more gas is moving outward,” said co-author Edmund Hodges-Kluck, an astronomer and XRISM team member at NASA Goddard. “Where do the three extra solar masses go? Do they escape out of the galaxy as hot gas some other way? We don’t know.”
“如果风以我们测量的速度稳定地吹动，那么我们认为它每年可以驱散四个太阳质量的气体，从而为更大、更冷的风提供动力。但 XRISM 告诉我们更多的气体正在向外移动，”合著者、天文学家、美国宇航局戈达德 XRISM 团队成员埃德蒙·霍奇斯-克卢克 (Edmund Hodges-Kluck) 说。 “额外的三个太阳质量去了哪里？它们是否以其他方式以热气体的形式逃逸出银河系？我们不知道。”
The XRISM satellite’s observations of M82 will help improve models of starburst galaxies, which may help scientists answer these types of questions in the future. NASA’s contributions to international projects like XRISM are part of the agency’s efforts to innovate with ambitious science missions that will help us better understand how our cosmos works.
XRISM卫星对M82的观测将有助于改进星暴星系模型，这可能有助于科学家在未来回答此类问题。 NASA 对 XRISM 等国际项目的贡献是该机构通过雄心勃勃的科学任务进行创新努力的一部分，这些任务将帮助我们更好地了解宇宙是如何运作的。
“Some of our early models of starburst galaxies were developed in the 1980s, and we’re finally able to test them in ways that weren’t possible before XRISM,” said co-author Skylar Grayson, a graduate student at Arizona State University in Tempe. “It provides opportunities to figure out why the model might not be capturing everything that’s going on in the real universe.”
“我们的一些早期星暴星系模型是在 20 世纪 80 年代开发的，我们终于能够以 XRISM 之前不可能的方式测试它们，”合著者、坦佩亚利桑那州立大学的研究生斯凯拉·格雷森 (Skylar Grayson) 说。 “它提供了弄清楚为什么模型可能无法捕捉真实宇宙中发生的一切的机会。”
By Jeanette Kazmierczak NASA’s Goddard Space Flight Center , Greenbelt, Md.
作者：Jeanette Kazmierczak 美国宇航局戈达德太空飞行中心，马里兰州格林贝尔特
Media Contact: Claire Andreoli 301-286-1940 NASA’s Goddard Space Flight Center, Greenbelt, Md.
媒体联系人：克莱尔·安德烈奥利 (Claire Andreoli) 301-286-1940 美国宇航局戈达德太空飞行中心，马里兰州格林贝尔特