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宇宙黑暗时代的探索与月基天文

Exploration of the cosmic dark ages and lunar based astronomy

  • 摘要: 宇宙黑暗时代是指宇宙大爆炸刚刚结束,第一代恒星和星系尚未形成的时期,这时的宇宙“鸿蒙未开”,蕴藏着宇宙起源阶段所遗留的大量宝贵信息。这一时期宇宙中性氢气体产生的21 cm信号为观测宇宙黑暗时代提供了探针,但这一信号现已红移到米波、十米波甚至百米波频段,在这一频段有其他天体特别是银河系产生的巨大前景辐射,在地球上的观测还受到地球电离层的吸收、折射以及多种电磁干扰,因此其观测具有极大的挑战性。利用月球背面或月球轨道进行观测具有优越的条件,可以避免电离层和电磁干扰对低频射电观测的影响。随着重返月球热潮的兴起,美国、欧洲、印度等国和中国都在积极酝酿月基天文特别是低频射电天文研究,打开低频电磁观测的新窗口,实现对宇宙黑暗时代和宇宙起源的探测。文章将介绍关于宇宙黑暗时代、宇宙黎明的研究进展以及利用月球开展低频射电天文观测的动向,并简要介绍中国提出的鸿蒙绕月卫星阵列计划。

     

    Abstract: The cosmic dark age refers to the era when the Big Bang has just ended and the first generation of stars and galaxies has not yet formed. At this time, the universe is in its primordial state, and much valuable information about its origin is still preserved. The 21 cm signal produced by the neutral hydrogen gas provides an observational probe of this cosmic dark age, but it is now redshifted to the meter wave, decameter wave or even hectometer wave band, where there are also other types of radiation, especially the huge galactic foreground radiation. It is also subject to absorption, refraction and various electromagnetic interferences by the ionosphere when observed from the ground, so its observation is extremely challenging. Observation from the far side of the Moon or along the lunar orbit, however, is ideal, as the ionosphere and low frequency radio interference can be avoided. With renewed interest in the exploration and utilization of our moon, the United States, Europe, India and China are actively planning research on moon-based astronomy, especially in the low-frequency radio band, which will open up a new window for astronomy and can probe the cosmic dark age and origin of the universe. This article will describe the latest research on the cosmic dark age and the cosmic dawn, as well as the current trend to use the moon to carry out low-frequency radio observations, and present a brief overview of the Discovering the Sky at the Longest wavelength (also known as the Hongmeng) lunar satellite array project.

     

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