哈勃太空望远镜的螺旋盘隆起特写

哈勃太空望远镜的螺旋盘隆起特写

ByNASA中文

This image from the NASA/ESA Hubble Space Telescope shows IC 2051, a galaxy in the southern constellation of Mensa (the Table Mountain) lying about 85 million light-years away. It is a spiral galaxy, as evidenced by its characteristic whirling, pinwheeling arms, and it has a bar of stars slicing through its center. This galaxy was observed for a Hubble study on galactic bulges, the bright round central regions of spiral galaxies. Spiral galaxies like IC 2051 are shaped a bit like flying saucers when seen from the side; they comprise a thin, flat disk, with a bulky bulge of stars in the center that extends above and below the disk. These bulges are thought to play a key role in how galaxies evolve, and to…

星系聚集带来温暖

星系聚集带来温暖

ByNASA中文

As the holiday season approaches, people in the northern hemisphere will gather indoors to stay warm. In keeping with the season, astronomers have studied two groups of galaxies that are rushing together and producing their own warmth. The majority of galaxies do not exist in isolation. Rather, they are bound to other galaxies through gravity either in relatively small numbers known as “galaxy groups,” or much larger concentrations called “galaxy clusters” consisting of hundreds or thousands of galaxies. Sometimes, these collections of galaxies are drawn toward one another by gravity and eventually merge. Using NASA’s Chandra X-ray Observatory, ESA’s XMM-Newton, the Giant Metrewave Radio Telescope (GMRT), and optical observations with the Apache Point Observatory in New Mexico, a team of astronomers has found that two…

哈勃望远镜拍摄到了银河系令人眼花缭乱的景象

哈勃望远镜拍摄到了银河系令人眼花缭乱的景象

ByNASA中文

NGC 3175 is located around 50 million light-years away in the constellation of Antlia (the Air Pump). The galaxy can be seen slicing across the frame in this image from the NASA/ESA Hubble Space Telescope, with its mix of bright patches of glowing gas, dark lanes of dust, bright core, and whirling, pinwheeling arms coming together to paint a beautiful celestial scene. The galaxy is the eponymous member of the NGC 3175 group, which has been called a nearby analog for the Local Group. The Local Group contains our very own home galaxy, the Milky Way, and around 50 others — a mix of spiral, irregular and dwarf galaxies. The NGC 3175 group contains a couple of large spiral galaxies — the subject of this…

船底座星云的“神秘山”

船底座星云的“神秘山”

ByNASA中文

Within the tempestuous Carina Nebula lies “Mystic Mountain.” This three-light-year-tall cosmic pinnacle, imaged by the Hubble Space Telescope’s Wide Field Camera 3 in 2010, is made up primarily of dust and gas, and exhibits signs of intense star-forming activity. The colors in this composite image correspond to the glow of oxygen (blue), hydrogen and nitrogen (green) and sulfur (red). Image Credit: NASA, ESA, M. Livio and the Hubble 20th Anniversary Team (STScI) 在汹涌的船底座星云中坐落着一座“神秘山”。2010年，哈勃太空望远镜的广角相机3号拍摄到了这个三光年高的宇宙尖塔，它主要由尘埃和气体组成，并显示出强烈的恒星形成活动的迹象。这张合成图中的颜色分别代表了氧(蓝色)、氢和氮(绿色)和硫(红色)的辉光。 图片来源:NASA, ESA, M. Livio and the Hubble 20th Anniversary Team (STScI)

黑洞孕育着百万光年之外的新星

黑洞孕育着百万光年之外的新星

ByNASA中文

Black holes are famous for ripping objects apart, including stars. But now, astronomers have uncovered a black hole that may have sparked the births of stars over a mind-boggling distance, and across multiple galaxies. If confirmed, this discovery, made with NASA’s Chandra X-ray Observatory and other telescopes, would represent the widest reach ever seen for a black hole acting as a stellar kick-starter. The black hole seems to have enhanced star formation more than one million light-years away. (One light year is equal to 6 trillion miles.) “This is the first time we’ve seen a single black hole boost star birth in more than one galaxy at a time,” said Roberto Gilli of the National Institute of Astrophysics (INAF) in Bologna, Italy, lead author of…

哈勃太空望远镜观测到一个发光的星系

哈勃太空望远镜观测到一个发光的星系

ByNASA中文

For this image, the NASA/ESA Hubble Space Telescope turned its powerful eye toward an emission-line galaxy called NGC 3749. When astronomers explore the contents and constituent parts of a galaxy somewhere in the universe, they use various techniques and tools. One of these is to spread out the incoming light from that galaxy into a spectrum and explore its properties. This is done in much the same way as a glass prism spreads white light into its constituent wavelengths to create a rainbow. By hunting for specific signs of emission from various elements within a galaxy’s spectrum of light —so-called emission lines — or, conversely, the signs of absorption from other elements — so-called absorption lines — astronomers can start to deduce what might be…

恒星在黑洞的深处诞生

恒星在黑洞的深处诞生

ByNASA中文

Located about 5.8 billion light years from Earth in the Phoenix Constellation, astronomers have confirmed the first example of a galaxy cluster where large numbers of stars are being born at its core. Galaxy clusters are the largest structures in the cosmos that are held together by gravity, consisting of hundreds or thousands of galaxies embedded in hot gas, as well as invisible dark matter. The largest supermassive black holes known are in galaxies at the centers of these clusters. For decades, astronomers have looked for galaxy clusters containing rich nurseries of stars in their central galaxies. Instead, they found powerful, giant black holes pumping out energy through jets of high-energy particles and keeping the gas too warm to form many stars. Now, scientists have…

哈勃太空望远镜发现了一个奇怪的螺旋

哈勃太空望远镜发现了一个奇怪的螺旋

ByNASA中文

The universe is simply so vast that it can be difficult to maintain a sense of scale. Many galaxies we see through telescopes such as the NASA/ESA Hubble Space Telescope, the source of this beautiful image, look relatively similar: spiraling arms, a glowing center, and a mixture of bright specks of star formation and dark ripples of cosmic dust weaving throughout. This galaxy, a spiral galaxy named NGC 772, is no exception. It actually has much in common with our home galaxy, the Milky Way. Each boasts a few satellite galaxies, small galaxies that closely orbit and are gravitationally bound to their parent galaxies. One of NGC 772’s spiral arms has been distorted and disrupted by one of these satellites (NGC 770 — not visible…

NASA探测到迄今为止最明亮的X射线爆发

NASA探测到迄今为止最明亮的X射线爆发

ByNASA中文

这幅插图描述了I型X射线爆发。这种类型的X射线爆发首先吹散氢层，氢层膨胀并最终消散。之后，不断增强的辐射积聚到一定点后会吹散氦层，氦层会超过膨胀的氢层。爆发过程中发射出的一些X射线从吸积盘上散射开来。然后火球迅速冷却，氦又重新回到脉冲星表面。 版权：NASA戈达德太空飞行中心/Chris Smith ，大学空间研究联合会（USRA） 美国东部时间8月20日晚10点04分左右，美国国家航空航天局（NASA）在国际空间站的中子星内部成分探测望远镜（Neutron star Interior Composition Explorer，NICER）探测到X射线的突然激增。这次X射线爆发是由脉冲星表面的大规模热核爆炸引起。脉冲星是很久以前超新星爆炸形成的恒星残骸。 这次X射线爆发是NICER探测到迄今为止最明亮的一次，爆发来自一个名为SAX J1808.4-3658的天体，简称J1808。关于这次爆发的观测结果揭示了许多从未在单次爆发中同时出现过的现象。此外，火球在逐渐减弱过程中重新短暂变亮了一下，天文学家们尚未找到能够解释这一现象的原因。 NASA戈达德太空飞行中心和马里兰大学帕克分校的天体物理学，首席研究员彼得•布尔特（Peter Bult）表示：“这次爆发非常突出。我们发现亮度经历了两个步骤的变化，我们认为这是由脉冲星表面不同层的喷射所导致，其他特征将帮助我们解读这些事件中所包含的物理学奥秘。” 天文学家们将这次爆发归类为I型X射线爆炸（Type I X-ray burst），它在20秒内释放了相当于太阳在近10天内所释放的能量。NICER在本次创纪录的喷射过程中所捕获到的细节将有助于天文学家们更好地理解驱动本次爆发以及其他暴态脉冲星热核爆炸的物理过程。 [rml_read_more] NASA的NICER所观测到的迄今为止最明亮的X射线爆发是由一颗名为J1808的脉冲星的热核爆炸所导致。这次X射线爆发发生于2019年8月20日，在20秒内释放了相当于太阳在近10天内所释放的能量。请点击视频查看科学家们对这一巨大爆发的发生是怎么认为的。 版权：NASA戈达德太空飞行中心 脉冲星是中子星的一种，是大质量恒星耗尽燃料在自身重量下坍缩并爆炸后所遗留下来的致密内核。脉冲星可以快速旋转，其两个磁极各有一个辐射波束。当脉冲星旋时，辐射束周期性地扫过我们的视线范围，形成有规律的高能辐射脉冲。 J1808位于约11000光年之外的人马座，每秒旋转401圈，是一个双星系统中的一员，其伴星是一颗褐矮星（大于巨行星，但又因质量太小不足以成为恒星）。一股稳定的氢气流从伴星流向中子星，并积聚在一个被称为吸积盘（accretion disk）的巨大存储结构中。 吸积盘中的气体不轻易向内移动。但是每隔几年，像J1808这样的脉冲星周围的吸积盘就会变得非常密集，以至于大量的气体被电离或失去电子。这使得光线更难穿过吸积盘。吸积盘内的能量开始了加热和电离的失控过程，从而捕获了更多能量。盘内气体变得越来越难以流动，并开始向内盘旋，最终落到脉冲星上。 氢气像雨点一样落在脉冲星表面，形成了一个越来越热、越来越深的全球“海洋”。在这一层底部，温度和压力不断升高直到发生将氢融合为氦的核融合反应，这一反应过程中伴随能量产生 – 这也是在太阳核心部分发生的过程。 戈达德戈达德太空飞行中心的NICER副首席研究员，同时也是论文共同作者的Zaven Arzoumanian表示：“氦气稳定下来形成了单独的氦层。当氦层达到几米深，条件将允许氦原子核融合成碳原子。然后氦会爆发释放出穿过整个脉冲星表面的热核火球。” 天文学家采用了一个名为爱丁顿极限（Eddington limit）的概念。这个概念是以英国天体物理学家阿瑟•爱丁顿爵士（Sir Arthur Eddington）而命名的，用来描述恒星在膨胀前的辐射强度上限值。该上限值很大程度上取决于发射源的上层物质组成。 论文共同作者，麻省理工学院物理学教授迪普托•查克拉巴蒂（Deepto Chakrabarty）表示：“我们的研究以一种新的方式诠释了这个存在已久的概念。我们显然看到了同一X射线爆发中两种不同成分的爱丁顿极限。这是追踪这次爆发事件背后核燃烧反应的一个非常强大而直接的方式。” 当爆发开始时，NICER的数据显示其X射线亮度先稳定了近一秒，然后再次以较慢的速度升高。研究人员将这种“停滞”（stall）解释为爆炸产生的能量积聚到足以将脉冲星的氢层吹入太空的那一瞬间。 火球继续持续了两秒后达到顶峰，吹散了更大的氦层。氦层的膨胀速度更快，在消散之前就超过了氢层，然后减速停止再回到脉冲星表面。在这一阶段之后，脉冲星短暂地变亮了约20%，研究团队尚未弄清其中的缘由。 在J1808最近一轮的活动中，NICER探测到了另一次相对微弱的X射线爆发，这次爆发中没有表现出在8月20日的爆发事件中所观察到的关键特征。 除了检测不同层的膨胀，NICER对爆发的观测还揭示了吸积盘的X射线反射，并记录了“爆发振荡”（burst oscillations）的闪烁现象 – X射线信号在脉冲星的自旋频率上下波动，但信号的发射位置与通常X射线辐射波束的位置不同。 关于描述这一发现的论文已经发表在《天体物理学杂志通讯》（ Astrophysical Journal Letters）上，可以戳阅此处进一步了解。 NICER是NASA探索者计划中的一项天体物理任务，该计划利用太阳物理学和天体物理学领域内的创新、简化和高效的管理方法，为世界级的科学研究提供频繁的飞行机会。NASA太空技术任务理事会对该任务的SEXTANT（Station Explorer for X-Ray Timing and Navigation Technology）组成部分提供支持。SEXTANT部分对基于脉冲的航天器导航进行演示。 来源： https://www.nasa.gov/feature/goddard/2019/nasas-nicer-catches-record-setting-x-ray-burst

一个正在形成的巨大星系群

一个正在形成的巨大星系群

ByNASA中文

Astronomers using data from the Chandra X-ray Observatory and other telescopes have put together a detailed map of a rare collision between four galaxy clusters. Eventually, all four clusters – each with a mass of at least several hundred trillion times that of the Sun – will merge to form one of the most massive objects in the universe. Galaxy clusters are the largest structures in the cosmos that are held together by gravity. Clusters consist of hundreds or even thousands of galaxies embedded in hot gas, and contain an even larger amount of invisible dark matter. Sometimes two galaxy clusters collide, as in the case of the Bullet Cluster, and occasionally more than two will collide at the same time. The new observations show…