无线电和雷达天文学(radio and radar astronomy)

通过测量天体发射或反射雷达波长的能量来研究天体。始於1931年，央斯基发现了来自地球外源的无线电波。1945年後，巨大的雷达圆盘天线、改进过的接收器和资料处理方法以及无线电干涉仪等，使得天文学家能够研究更昏暗的源并得到更多的细节。无线电波能穿透太空中大多数的气体和尘埃，比起光学观察来，能给出银河系中心清楚得多的图像以及银河系的结构。这样就能研究我们的银河系中的星际物质，发现以前不知道的宇宙天体（例如，脉冲星、类星体）。在雷达天文学中，无线电信号送往接近地球的天体或现象（例如，流星尾迹、月球、小行星、附近的行星），然後测出它们的回波，从而提供目标的距离及其表面结构的精确测量结果。由於雷达波能够穿透浓密的云层，所以它为我们提供了金星表面的唯一地图。在人类登上月球以前，对月球所作的无线电和雷达研究就已经揭示了月球的沙质表面。无线电观察也提供了关於太阳的许多知识。亦请参阅radio telescope。

English version：

radio and radar astronomy

Study of celestial bodies by measuring the energy they emit or reflect at radio wavelengths. It began in 1931 with Karl Jansky's discovery of radio waves from an extraterrestrial source. After 1945, huge radar-dish antennas, improved receivers and data-processing methods, and radio interferometers let astronomers study fainter sources and obtain greater detail. Radio waves penetrate much of the gas and dust in space, giving a much clearer picture of the center and structure of the Milky Way than optical observation can. This has allowed detailed studies of the interstellar medium in our galaxy and the discovery of previously unknown cosmic objects (e.g., pulsars, quasars). In radar astronomy, radio signals are sent to near-earth bodies or phenomena (e.g., meteor trails, the moon, asteroids, nearby planets) and the reflections measured, providing precise measurement of the objects' distances and surface structure. Because radar waves can penetrate even dense clouds, they have provided our only maps of the surface of Venus. Radio and radar studies of the moon revealed its sandlike surface before landings were made. Radio observations have also contributed greatly to knowledge about the sun. See also radio telescope.