“XMM-牛顿”望远镜 发现部分宇宙中丢失的物质
6 May 2008ESA’s orbiting X-ray observatory XMM-Newton has been used by a team of international astronomers to uncover part of the missing matter in the universe.
2008年5月6日
一组国际天文学家使用ESA的“XMM-牛顿”X射线轨道天文台揭示了宇宙中部分“丢失”的物质。
[url=http://a1862.g.akamai.net/7/1862/14448/v1/esa.download.akamai.com/13452/g696_fast_mpeg4.avi]flv格式的演示[attach]128686[/attach][/url]
或者去原址 [url]http://www.esa.int/esaCP/SEMQLPZXUFF_index_1.html[/url] 看
10 years ago, scientists predicted that about half of the missing ‘ordinary’ or normal matter made of atoms exists in the form of low-density gas, filling vast spaces between galaxies.
10年前，科学家们预言大约有一半由原子组成的“丢失”了的普通物质，以低密度气体的形式存在于星系间广阔的空间中。
All the matter in the universe is distributed in a web-like structure. At dense nodes of the cosmic web are clusters of galaxies, the largest objects in the universe. Astronomers suspected that the low-density gas permeates the filaments of the web.
宇宙中的所有物质都分布在一个网状的结构中。宇宙网的密集节点就是星系群，宇宙中的最大天体。天文学家怀疑低密度气体充斥在这个丝网之中。
The low density of the gas hampered many attempts to detect it in the past. With XMM-Newton’s high sensitivity, astronomers have discovered its hottest parts. The discovery will help them understand the evolution of the cosmic web.
过去许多探测低密度气体的努力都受到了阻碍。借助“XMM-牛顿”的高灵敏度，天文学家们发现了其中最热的一部分。该发现将有助于其了解宇宙网的演化。
Only about 5% of our universe is made of normal matter as we know it, consisting of protons and neutrons, or baryons, which along with electrons, form the building blocks of ordinary matter. The rest of our universe is composed of elusive dark matter (23%) and dark energy (72%).
我们知道我们的宇宙只有约5%是由质子和中子（也称重子）以及电子这些普通物质构成，剩下的由难以捉摸的暗物质（23%）和暗能量（72%）组成。
Small as the percentage might be, half of the ordinary baryonic matter is unaccounted for. All the stars, galaxies and gas observable in the universe account for less than a half of all the baryons that should be around.
这可能是个很小的百分比，有一半的普通重子物质还没有考虑到。宇宙中所有观测到的恒星、星系和气体总和还不到应该存在的重子的一半。
Scientists predicted that the gas would have a high temperature and so it would primarily emit low-energy X-rays. But its very low density made observation difficult.
科学家们预言气体温度可能很高于是会主要发射出低能的X射线。但是其过低的密度给观测带来困难。
[img]http://www.esa.int/images/A2223xray_H.jpg[/img]
Composite optical and X-ray image of galaxy clusters Abell 222 and Abell 223. The cluster pair is connected by a filament permeated by hot X-ray emitting gas.
Abell 222和Abell 223合成了光学和X射线的图像。两星系群被一条充满散发X射线的热气体纤维连接起来。。
The optical image was obtained by SuprimeCam at the Subaru telescope, the X-ray image showing the distribution of the diffuse hot gas (yellow to red) was obtained by XMM-Newton.
光学图像来自 Subaru 望远镜的主焦点相机，来自““XMM-牛顿””的X射线图像显示了弥散热气体（从黄到红）的分布。
感谢: ESA/ XMM-Newton/ EPIC/ ESO (J. Dietrich)/ SRON (N. Werner)/ MPE (A. Finoguenov)
Astronomers using XMM-Newton were observing a pair of galaxy clusters, Abell 222 and Abell 223, situated at a distance of 2300 million light-years from Earth, when the images and spectra of the system revealed a bridge of hot gas connecting the clusters.
天文学家使用“XMM-牛顿”观测一对星系群（Abell222和Abell223，距地球23亿光年）的时候，该系统的图像和光谱展示了一条连接两星系群的热气体桥。
"The hot gas that we see in this bridge or filament is probably the hottest and densest part of the diffuse gas in the cosmic web, believed to constitute about half the baryonic matter in the universe," says Norbert Werner from SRON Netherlands Institute for Space Research, leader of the team reporting the discovery.
报告这一发现的领队，来自荷兰空间研究会（SRON Netherlands Institute for Space Research）的Norbert Werner说：“我们看到的这个桥或纤维中的热气体可能是弥漫在宇宙网中气体密度最高、最热的部分，这些气体被认为构成宇宙中约一半的重子物质。”
[img]http://www.esa.int/images/Cosmic_web_H.jpg[/img]
This is a model of the cosmic web. Clusters of galaxies are expected to develop at the intersections of the web.
这是宇宙网的一个模型。星系群被认为在网的交叉点处成长。
感谢: Springel et al., Virgo Consortium
“The discovery of the warmest of the missing baryons is important. That’s because various models exist and they all predict that the missing baryons are some form of warm gas, but the models tend to disagree about the extremes,” adds Alexis Finoguenov, a team member.
“发现最热的丢失了的重子是很重要的。这是因为多种已有模型都预言丢失了的重子是某种形式的暖气体，不过模型对于极值并不一致。”小组成员Alexis Finoguenov补充道。
Even with XMM-Newton’s sensitivity, the discovery was only possible because the filament is along the line of sight, concentrating the emission from the entire filament in a small region of the sky. The discovery of this hot gas will help better understand the evolution of the cosmic web.
也只有“XMM-牛顿”的灵敏度才能使发现成为可能，这是由于纤维是沿着视线的，把一小块天区里整个纤维散发出的光都集中起来了。这一热气体的发现将有助于更好的了解宇宙网的演化。
"This is only the beginning. To understand the distribution of the matter within the cosmic web, we have to see more systems like this one. And ultimately launch a dedicated space observatory to observe the cosmic web with a much higher sensitivity than possible with current missions. Our result allows to set up reliable requirements for those new missions." concludes Norbert Werner.
“这只是开始。要了解宇宙网中的物质分布，我们需要看到更多这样的系统。并最终要发射一个观测宇宙网专用的比现有系统灵敏度更高的空间望远镜。我们的成果为这些任务提供了可信的需求。”Norbert Werner总结道。
ESA’s XMM-Newton Project Scientist, Norbert Schartel, comments on the discovery, “This important breakthrough is great news for the mission. The gas has been detected after hard work and more importantly, we now know where to look for it. I expect many follow-up studies with XMM-Newton in the future targeting such highly promising regions in the sky.”
ESA “XMM-牛顿”项目科学家 Norbert Schartel 对这一发现的评论是：“这一重要突破对该任务来说是个好消息。在做了大量工作之后才发现这一气体，更重要的是现在我们知道到哪儿去找它了。我期望将来有更多使用‘XMM-牛顿’的后续研究瞄准天上像这样很有希望的区域。”
[[i] 本帖最后由 Rojer. 于 2008-5-9 01:13 编辑 [/i]] ::070821_16.jpg:: AVI的演示不显示么？ 学习了, 呵呵! 楼主的Einstein 分数好高哦! ::070821_09.jpg:: ::070821_09.jpg::
::42:: 本人的EINSTEIN：2132，SETI：1866::070821_05.jpg:: 06年的时候平均每天5千多分飙了一百万::070821_04.jpg::
发现个错字.....::070821_05.jpg:: 又一幅知识酷图！
可惜噪点有点大。。。
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