A powerful collision of galaxy clusters has been captured by NASA's Hubble Space Telescope and Chandra X-ray Observatory. This clash of clusters provides striking evidence for dark matter and insight into its properties.
The observations of the cluster known as MACS J0025.4-1222 indicate that a titanic collision has separated the dark from ordinary matter and provide an independent confirmation of a similar effect detected previously in a target dubbed the Bullet Cluster. These new results show that the Bullet Cluster is not an anomalous case.
MACS J0025 formed after an enormously energetic collision between two large clusters. Using visible-light images from Hubble, the team was able to infer the distribution of the total mass -- dark and ordinary matter. Hubble was used to map the dark matter (colored in blue) using a technique known as gravitational lensing. The Chandra data enabled the astronomers to accurately map the position of the ordinary matter, mostly in the form of hot gas, which glows brightly in X-rays (pink).
As the two clusters that formed MACS J0025 (each almost a quadrillion times the mass of our sun) merged at speeds of millions of miles per hour, the hot gas in the two clusters collided and slowed down, but the dark matter passed right through the smashup. The separation between the 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.
Image Credit: NASA, ESA, CXC, M. Bradac (University of California, Santa Barbara), and S. Allen (Stanford University)
暗物质兰色，普通物质粉红色。作者: hiblue 时间: 2009-1-2 13:01
这是关于暗物质的文章的插图，不懂得什么意思。作者: AUV 时间: 2009-1-3 19:54
MACSJ0025: Two Giant Galaxy Clusters Collide
What happens when two of the largest objects in the universe collide? No one was quite sure, but the answer is giving clues to the nature of mysterious dark matter. In the case of MACSJ0025.4-1222, two huge clusters of galaxies have been found slowly colliding over hundreds of millions of years, and the result has been imaged by both the Hubble Space Telescope in visible light and the Chandra Space Telescope in X-ray light. Once the above visible image was recorded, the location and gravitational lens distortions of more distant galaxies by the newly combined galaxy cluster allowed astronomers to computationally determine what happened to the clusters' dark matter. The result indicates that this huge collision has caused the dark matter in the clusters to become partly separated from the normal matter, confirming earlier speculation. In the above combined image, dark matter is shown as the diffuse purple hue, while a smoothed depiction of the X-ray hot normal matter is shown in pink. MACSJ0025 contains hundreds of galaxies, spans about three million light years, and lies nearly six billion light years away (redshift 0.59) toward the constellation of Monster Whale (Cetus).
自己翻的，不一定准确
MACSJ0025：两个巨大星系团的碰撞
当宇宙中两个最大的天体碰撞时会发生什么？没人能准确地知道，但神秘的暗物质可能给与答案。在MACSJ0025.4-1222中，发现两个巨大的星系团在数亿年的时间里慢慢的碰撞着，哈勃在光学波段、钱德拉空间望远镜在X射线波段记录了碰撞的结果。当光学照片被记录到时，这个新形成的星系团里的遥远星系的位置和由引力透镜效应造成的扭曲，让天文学家可以计算星系团中的暗物质发生了什么变化。结果表明这次巨大的碰撞导致了星系团里的暗物质与正常物质分离，从而证实了先前的猜测。在这张合成的图像中，暗物质由弥漫的紫色表示，正常物质发射的X射线由粉色表示。MACSJ0025包含了数百个星系，跨度大约300万光年，位于鲸鱼座，距离我们将近60亿光年远（红移0.59）。
