Studying black holes using the Event Horizon Telescope

使用事件视界望远镜研究黑洞

• 批准号: 2738551
• 金额: --
• 依托单位: University of Central Lancashire
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2738551
• 关键词: Studying; black; holes; using; Event

Supermassive black holes are some of the largest and most extreme individual objects found in the Universe. While the black hole itself cannot be observed, the gas in an accretion disk surrounding the black hole is significantly heated by friction, causing it to glow. This forms a distinct boundary between the dark central region, called a black hole shadow, which is surrounded by a bright ring structure. The shadow and the ring structure surrounding it are predicted by Einstein's theory of general relativity and they can be used to test the theory in exciting ways.In 2019 the Event Horizon Telescope (EHT) released the first image of the shadow created by a supermassive black hole. Using a global interferometry array at 1.3mm, the collaboration was able to image the shadow of the supermassive black hole at the centre of the nearby galaxy M87. In 2022 the EHT released an image of the shadow of the supermassive black hole at the centre of the Milky Way, Sagittarius A*.The data that produced both images was collected in 2017, the image of Sagittarius A* took much longer to process than the image of M87* due to two main constraints, the interstellar scattering, and the increased variability. When looking into the centre of our galaxy, the Milky Way, interstellar scattering has a significant effect on the images, this had to be accounted for when processing the image, this is not the case when observing M87*. Sagittarius A* is approximately 1500 times less massive and therefore has a radius approximately 1500 times smaller than M87*. This means the dynamical timescale, which is the period of the innermost stable circular orbit, is much longer for M87*. The dynamical timescale for M87* is estimated to be between 5 days and 1 month, depending on the spin of M87*, for Sagittarius A* the dynamical timescale is between 4 and 30 minutes. So, the source structure can change over an observational run for Sagittarius A*, but not M87*, this also had to be accounted for. Both factors increased the length of time required to fully produce and analyse the results for both black holes.Through this project and the collaboration with the EHT, I will investigate the shadows around the supermassive black holes Sagittarius A* and M87*. Fortunately, there are many different areas available to further understand black hole shadows. One promising area that I hope to explore is the new data from the 2018 observing run, with additional telescope facilities, which increased the (u,v) coverage, which will lead to improved results compared to the 2017 observations. Comparisions between the 2017 and 2018 data is also an interesting area to explore, this could lead to a better understanding of the hotspots that appear on the images, especially on Sagittarius A*, which has 3 bright spots. If these spots are in the same position or if they have moved around the ring of Sagittarius A* could say if they are physical bright spots in the ring which could be explored. If instead they are stationary, they might be an artifact created while processing the data. Later observing runs with an ever-growing network of satellites will improve on this further.Another exciting area that can be explored is the polarization of the black holes, this has been completed for M87*, but not for Sagittarius A* yet. The polarization of the light being emitted from the disk around the shadow can reveal information about the magnetic field structure near the event horizon of the black hole. Along with the global array of radio telescopes that make up the EHT, simulations will be a key tool throughout this project. General Relativistic Magnetohydrodynamical Dynamics (GRMHD) simulations, describe both Einstein's theory of general relativity and magnetohydrodynamics. Therefore, they can be used to model accretion and jet formation in the vicinity of black holes which is critical for understanding the images of Sagittarius A* and M87* captured by the EHT.

超级质量黑洞是宇宙中发现的最大，最极端的物体。尽管无法观察到黑洞本身，但黑洞周围的积聚盘中的气体被摩擦显着加热，从而使其发光。这形成了一个被称为黑洞阴影的深色中央区域之间的独特边界，该区域被明亮的环结构所包围。爱因斯坦的一般相对论理论预测了阴影及其周围的环结构，它们可用于以令人兴奋的方式测试理论。在2019年，事件地平线望远镜（EHT）发布了由超级质量黑洞创建的阴影的第一张图像。该协作使用1.3mm的全球干涉率阵列，能够对附近Galaxy M87中心的超大质量黑洞的阴影进行想象。 2022年，EHT发布了银河系中心的超级质量黑洞的阴影图像，射手座A*。产生这两个图像的数据是在2017年收集的，射手座A*的图像比M87*的图像要比M87*的图像要长得多，而M87的图像由于两个主要约束，并增加了散射性，并增加了散射性。当观察我们银河系的中心，银河系，星际散射对图像有重大影响，在处理图像时必须考虑这一点，在观察M87*时，情况并非如此。 Sagittarius A*的量较小约1500倍，因此半径约为M87*的1500倍。这意味着对于M87*来说，动态时间尺度是最内向稳定的圆形轨道的时期。 M87*的动力学时间尺度估计在5天到1个月之间，具体取决于M87*的自旋，对于射手座A*，动态时间尺度在4到30分钟之间。因此，源结构可以通过射手座A*的观察性运行来改变，但也不得将M87*变化，这也必须考虑到这一点。这两个因素都增加了充分生产和分析黑洞结果所需的时间长度。通过该项目以及与EHT的合作，我将研究超级质量黑洞Sagittarius A*和M87*周围的阴影。幸运的是，有许多不同的区域可以进一步了解黑洞阴影。我希望探索的一个有希望的领域是2018年观察跑步的新数据，以及其他望远镜设施，这增加了（u，v）的覆盖范围，与2017年的观察相比，这将导致结果改善。 2017年和2018年数据之间的比较也是一个有趣的领域，这可能会导致对图像上出现的热点有更好的了解，尤其是在射手座A*上，它具有3个亮点。如果这些斑点处于相同的位置，或者它们在射手座A的环上移动，可以说它们是否是可以探索的环中的亮点。相反，如果它们是静止的，那么它们可能是在处理数据时创建的工件。后来观察到不断增长的卫星网络将进一步改善跑步。另一个可以探索的令人兴奋的区域是黑洞的两极分化，这已经完成了M87**，但对于Sagittarius A*而言，这还没有。阴影周围磁盘发出的光的极化可以揭示有关黑洞事件范围附近磁场结构的信息。与构成EHT的全球射电望远镜一起，模拟将成为整个项目的关键工具。一般相对论的磁流失动力学（GRMHD）模拟，描述了爱因斯坦的一般相对论和磁流失动力学理论。因此，它们可用于在黑洞附近建模积聚和喷射形成，这对于理解射手座A*和M87*的图像至关重要。