中國新發射衛星有望揭開暗物質之謎

新華社酒泉12月17日電 中國周四將首枚用於探測暗物質的空間望遠鏡送入太空，這是人類在尋找暗物質進程中邁出的最新一步。這種神秘物質佔據了宇宙總質量的絕大部分，人類卻看不見。

清晨8點12分，長征二號丁運載火箭背負著暗物質粒子探測衛星（DAMPE）從酒泉衛星發射中心騰空而起。衛星以中國古典名著《西游記》中有著火眼金睛的美猴王“悟空”命名。

它將進入地球上空５００公裡高的太陽同步軌道，從那裡觀測太空中高能粒子的能量、方向和電荷。

“悟空”的設計壽命長達三年，不過科學家期望它能在軌工作五年。

在此期間，科學家希望這枚1.9噸重、如書桌般大小的人造衛星能幫助人類揭開暗物質的神秘面紗。

暗物質是現代科學的一大謎團，它既不釋放也不反射電磁輻射，因而人類無法直接觀測。

科學家早先引入暗物質的概念，用以解釋宇宙間的質量缺失以及光在遙遠星系中的異常彎折現象。如今，暗物質已被物理學界普遍接受，但科學家仍未能探測到其存在的直接証據。

科學家相信，我們已知的宇宙中，包括質子、中子、電子等構成的普通物質僅佔約５％，其余都是看不見的暗物質和暗能量。

暗物質粒子探測衛星首席科學家常進說，揭開暗物質之謎對物理科學和空間科學具有革命性意義，讓人類可以更清晰地理解星系和宇宙的歷史與未來演變。

此前，科學家已通過國際空間站搭載的阿爾法磁譜儀，以及位於瑞士日內瓦城郊的歐洲核子研究中心（CERN）的大型強子對撞機（LHC）等裝置探索暗物質的真實屬性，並取得了一些成果。

中國還在西南部的四川建立了地球上最深的暗物質實驗室，位於地下約2400米的深處。

而最新發射的暗物質粒子探測衛星將幫助科學家搜尋暗物質湮滅或衰變的証據。

“這就像是去尋找暗物質的‘兒子’，如果找不到‘爸爸’，那麼我們總可以去找他的‘兒子’，並且從‘兒子’那裡得到‘爸爸’的一些信息。”常進說。

“悟空”將在發射后的前兩年對全天掃描，之后根據探測結果，對暗物質最可能出現的區域定向觀測。

100多名中國科學家將對衛星數據展開分析研究。首批科學成果有望在2016年下半年發布。

常進說，“悟空”是世界上迄今為止觀測能段范圍最寬、能量分辨率最優的暗物質探測器。

據介紹，這枚新型探測衛星的觀測能段大約是國際空間站阿爾法磁譜儀的１０倍，能量分辨率則比國際同類探測器至少高３倍以上。

不過，常進也謹慎地表示，科學家對在這次任務中找到暗物質的蹤跡還沒有十足把握。

“暗物質的物理性質還沒有弄清楚，沒有人能百分之百保証衛星一定能找到暗物質。”常進說。

“但隻要它工作正常，就為我們打開了一扇新窗口。”常進說，“悟空”除了尋找暗物質外，還是一個宇宙射線望遠鏡，可以研究宇宙射線的起源、傳播和加速。

“悟空”是中國科學院四顆科學衛星系列的首發星。

另外三顆科學衛星，包括一顆量子科學實驗衛星、實踐十號返回式科學實驗衛星以及一顆用於觀測黑洞、中子星等重要天體的硬Ｘ射線調制望遠鏡衛星，將在明年陸續發射。

中國科學院國家空間科學中心主任吳季透露，這三顆科學衛星目前研制進展順利。

“中國不應只是空間知識的使用者，也應成為空間知識的創造者。”他說。

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.