微波背景辐射双极化: 地球高速穿过宇宙的效应

2022年4月3日

CMB Dipole: Speeding Through the Universe
Image Credit: DMR, COBE, NASA, Four-Year Sky Map

Explanation: Our Earth is not at rest. The Earth moves around the Sun. The Sun orbits the center of the Milky Way Galaxy. The Milky Way Galaxy orbits in the Local Group of Galaxies. The Local Group falls toward the Virgo Cluster of Galaxies. But these speeds are less than the speed that all of these objects together move relative to the cosmic microwave background radiation (CMBR). In the featured all-sky map from the COBE satellite in 1993, microwave light in the Earth’s direction of motion appears blueshifted and hence hotter, while microwave light on the opposite side of the sky is redshifted and colder. The map indicates that the Local Group moves at about 600 kilometers per second relative to this primordial radiation. This high speed was initially unexpected and its magnitude is still unexplained. Why are we moving so fast? What is out there?

Tomorrow’s picture: auroral vortex

微波背景辐射双极化: 地球高速穿过宇宙的效应
影像提供: DMR, COBE, NASA, Four-Year Sky Map

说明: 我们的地球并非静止不动。地球绕着太阳运行；太阳绕着银河系的中心打转；银河系在本星系群里运动；本星系群则掉向室女座星系团。然而，这些运动的速率皆小于这些天体一起相对于宇宙微波背景辐射 (CMBR)运动的速率。在这幅由COBE卫星摄于1993年的主题全天图里，沿着地球运动方向的辐射，出现了蓝移，因此显得较热，而反方天空的微波辐射，出现出红移，因而看起来较冷。这张图显示相对于这种本初辐射，本星系群的运动速度大约是每秒600公里。这种原先未预期的高速，到目前为止尚无合理的解释。为何本星系群会动得这么快呢？外头到底有什么在牵引我们？

明日的图片: auroral vortex