中国新发射卫星有望揭开暗物质之谜

新华社酒泉12月17日电 中国周四将首枚用于探测暗物质的空间望远镜送入太空，这是人类在寻找暗物质进程中迈出的最新一步。这种神秘物质占据了宇宙总质量的绝大部分，人类却看不见。

清晨8点12分，长征二号丁运载火箭背负着暗物质粒子探测卫星（DAMPE）从酒泉卫星发射中心腾空而起。卫星以中国古典名著《西游记》中有着火眼金睛的美猴王“悟空”命名。

它将进入地球上空５００公里高的太阳同步轨道，从那里观测太空中高能粒子的能量、方向和电荷。

“悟空”的设计寿命长达三年，不过科学家期望它能在轨工作五年。

在此期间，科学家希望这枚1.9吨重、如书桌般大小的人造卫星能帮助人类揭开暗物质的神秘面纱。

暗物质是现代科学的一大谜团，它既不释放也不反射电磁辐射，因而人类无法直接观测。

科学家早先引入暗物质的概念，用以解释宇宙间的质量缺失以及光在遥远星系中的异常弯折现象。如今，暗物质已被物理学界普遍接受，但科学家仍未能探测到其存在的直接证据。

科学家相信，我们已知的宇宙中，包括质子、中子、电子等构成的普通物质仅占约５％，其余都是看不见的暗物质和暗能量。

暗物质粒子探测卫星首席科学家常进说，揭开暗物质之谜对物理科学和空间科学具有革命性意义，让人类可以更清晰地理解星系和宇宙的历史与未来演变。

此前，科学家已通过国际空间站搭载的阿尔法磁谱仪，以及位于瑞士日内瓦城郊的欧洲核子研究中心（CERN）的大型强子对撞机（LHC）等装置探索暗物质的真实属性，并取得了一些成果。

中国还在西南部的四川建立了地球上最深的暗物质实验室，位于地下约2400米的深处。

而最新发射的暗物质粒子探测卫星将帮助科学家搜寻暗物质湮灭或衰变的证据。

“这就像是去寻找暗物质的‘儿子’，如果找不到‘爸爸’，那么我们总可以去找他的‘儿子’，并且从‘儿子’那里得到‘爸爸’的一些信息。”常进说。

“悟空”将在发射后的前两年对全天扫描，之后根据探测结果，对暗物质最可能出现的区域定向观测。

100多名中国科学家将对卫星数据展开分析研究。首批科学成果有望在2016年下半年发布。

常进说，“悟空”是世界上迄今为止观测能段范围最宽、能量分辨率最优的暗物质探测器。

据介绍，这枚新型探测卫星的观测能段大约是国际空间站阿尔法磁谱仪的１０倍，能量分辨率则比国际同类探测器至少高３倍以上。

不过，常进也谨慎地表示，科学家对在这次任务中找到暗物质的踪迹还没有十足把握。

“暗物质的物理性质还没有弄清楚，没有人能百分之百保证卫星一定能找到暗物质。”常进说。

“但只要它工作正常，就为我们打开了一扇新窗口。”常进说，“悟空”除了寻找暗物质外，还是一个宇宙射线望远镜，可以研究宇宙射线的起源、传播和加速。

“悟空”是中国科学院四颗科学卫星系列的首发星。

另外三颗科学卫星，包括一颗量子科学实验卫星、实践十号返回式科学实验卫星以及一颗用于观测黑洞、中子星等重要天体的硬Ｘ射线调制望远镜卫星，将在明年陆续发射。

中国科学院国家空间科学中心主任吴季透露，这三颗科学卫星目前研制进展顺利。

“中国不应只是空间知识的使用者，也应成为空间知识的创造者。”他说。

英文原文：

New satellite to shed light on invisible dark matter

JIUQUAN, Gansu, Dec. 17 (Xinhua) -- Chinaon Thursday sent into space the country's first space telescope in a fresh search for signals of dark matter, invisible material that scientists say makes up most of the universe's mass.

The Dark Matter Particle Explorer (DAMPE) Satellite, which has been given the moniker "Wukong" after the character the Monkey King, from the Chinese classical fiction "Journey to the West," which has penetrating eyes, was launched at 8:12 a.m. Thursday on a Long March 2-D rocket from Jiuquan Satellite Launch Center.

It will enter a sun-synchronous orbit at a height of 500 kilometers to observe the direction, energy and electric charge of high-energy particles in space.

The satellite is designed to undertake a three-year space mission, but scientists hope it could last five.

During that period, scientists hope the 1.9-tonne desk-sized satellite could help shine more light on the hypothetical mass.

Dark matter, which does not emit or reflect enough electromagnetic radiation to be observed directly, is one of the huge mysteries of modern science.

Theorized by scientists who could not understand missing mass and strangely bent light in faraway galaxies, dark matter has become widely accepted in the physics community even though its existence has never been concretely proven.

Scientists now believe that only around five percent of the total mass-energy of the known universe is made up of ordinary matter -- protons, neutrons, electrons -- whereas dark matter and dark energy make up the rest.

Exploration of dark matter could, therefore, give us a clearer idea about the past and future of galaxies and the universe, and will be revolutionary for the world of physics and space science, said Chang Jin, chief scientist on the project.

Hints of the true nature of dark matter have already emerged from some previous observations, including those conducted by the Alpha Magnetic Spectrometer onboard the International Space Station and by the Large Hadron Collider (LHC) at the CERN physics research center near Geneva, Switzerland.

China also runs an underground dark matter lab in the southwest province of Sichuan, some 2,400 meters under the earth's surface.

The new DAMPE satellite will help scientists look for evidence of dark matter annihilation or decay.

"This is like tracking down the 'son' of dark matter -- if you cannot find the father, you go to the son and you could learn about at least some properties of his father," said Chang.

Wukong will scan space in all directions in the first two years and focus on sections where dark matter is most likely to be observed afterward.

More than 100 scientists will study the data. Initial findings will be published in the second half of 2016.

Chang said Wukong has the widest observation spectrum and highest energy resolution of any dark-matter probe in the world.

The new satellite's observation spectrum is approximately nine times wider than the Alpha Magnetic Spectrometer onboard the International Space Station, while its energy resolution is at least three times higher than its international peers, according to Chang.

However, he cautioned, there is no guaranteed success in the mission.

"We have not entirely figured out the physical properties of dark matter, so no one is one hundred percent sure that the satellite can find it," Chang said.

"As long as Wukong keeps working, it will open a new window for our search," he said, adding that the satellite could also serve as a cosmic ray telescope and be used to study the origin, transportation and acceleration of cosmic rays.

Wukong is first of four scientific satellites under aChineseAcademyof Sciences (CAS) space program.

The other three satellites -- one for quantum science experiments, another for microgravity research and space life science, and a hard X-ray telescope which will observe black holes, neutron stars and other phenomena -- will be launched next year.

Wu Ji, director of the National Space Science Center under CAS, said development of the other three satellites is going well.

"China[...] should not only be the user of space knowledge, we should also be the creator," Wu said.