BYR Achieve · 镜像论坛

好久没有新贴，贴个新闻上来吧，我感觉还是很有趣的。这是哈勃在8月28日发布的新照片。懒得完全翻译了，大致说说意思。照片中是两个星系团（MACSJ0025.4-1222）正在发生碰撞，现在正处于互相穿过的过程中。利用哈勃望远镜的光学图像，天文学家可以得到总质量的分布（普通物质和暗物质）。再利用引力透镜效应，哈勃可以得到暗物质的分布，在图中标为蓝色。而钱德拉X射线天文台（空间望远镜）能够得到精确的普通物质的分布，图中标记为红色。照片中可见，当两个星系团相互穿透时，普通物质粒子由于各种相互作用而大幅减速处在中间，但暗物质则顺利相互穿过，把普通物质甩在后边。该现象支持了此前的观点：除了引力之外，暗物质粒子间只有很弱的相互作用，或者完全没有。后附原文 http://www.spacetelescope.org/news/html/heic0818.html News Release - heic0818: Clash of clusters provides new dark matter clue Click for larger image. 27-Aug-2008: A powerful collision between galaxy clusters has been captured by the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory. This clash of clusters provides striking evidence for dark matter and insight into its properties. New Hubble and Chandra observations of the cluster known as MACSJ0025.4-1222 indicate that a titanic collision has separated dark from ordinary matter. This provides independent confirmation of a similar effect detected previously in a target dubbed the Bullet Cluster, showing that the Bullet Cluster is not an anomalous case. MACSJ0025 formed after an enormously energetic collision between two large clusters. Using visible-light images from Hubble, astronomers were able to infer the total mass distribution — dark and ordinary matter. Hubble was used to map the dark matter (coloured in blue) using a technique known as gravitational lensing. Chandra data enabled the astronomers to accurately map the ordinary matter, mostly in the form of hot gas, which glows brightly in X-rays (shown in pink). As the two clusters that formed MACSJ0025 (each almost a whopping quadrillion times the mass of our Sun) merged at speeds of millions of kilometres per hour, hot gas in the two clusters collided and slowed down, but the dark matter passed right through this smash-up. The separation between material shown in pink and blue therefore provides observational evidence for dark matter and supports the view that dark matter particles interact with each other only very weakly or not at all, apart from the pull of gravity. The international team of astronomers in this study was led by Maruša Bradač of the University of California, Santa Barbara, USA, and Steve Allen of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University and the Stanford Linear Accelerator Center (SLAC), USA. Their results will appear in an upcoming issue of The Astrophysical Journal. Notes for editors: The Hubble Space Telescope is a project of international cooperation between ESA and NASA. Image credit: NASA, ESA, CXC, M. Bradač (University of California, Santa Barbara, USA), and S. Allen (Stanford University, USA).

星系团碰撞提供新的暗物质的线索