OBSERVATION OF A RAPIDLY PULSATING RADIO SOURCE
OBSERVATION OF A RAPIDLY PULSATING RADIO SOURCE
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DOI：
10.1038/217709a0
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发表时间：
1968-01-01
期刊：
影响因子：
64.8
通讯作者：
COLLINS, RA
中科院分区：
文献类型：
--
作者：
HEWISH, A;BELL, SJ;COLLINS, RA
一系列的观测最终导致了脉冲射电源或脉冲星的意外发现，始于安东尼·休伊什对电离层和日冕中等离子体云运动引起的离散射电源闪烁的开创性研究。[1]当电离层中的风将云层吹过视线到达小型射电源时，干扰会引起接收强度的波动，时间尺度约为30秒;同样，太阳风也会引起时间尺度为零点几秒的快速波动。休伊什意识到，对这些波动的观测将提供一种探测致密射电源的简单方法。此外，由于遥远的射电星系和类恒星天体的角尺寸很小，因此获得有关这些源的角尺寸的定量信息的一种方法是研究当它们以相对于太阳的不同角度被观察时它们的波动如何变化。因此，休伊什和他的同事们建造了一个由2,048个偶极子组成的阵列，这些偶极子分布在18,000平方米的面积上，以提供高灵敏度，并在3.7米的长波长下工作，因为已知波动在较长波长下更突出。研究生乔斯林·贝尔被指派负责使用该仪器在相对于太阳的许多不同角度对几个射电源进行重复观测。贝尔每周都认真分析约400英尺的图表记录，很快就发现无线电天空充满了紧凑的源。到了八月中旬，她发现了一个神秘的源头，它在太阳风的影响应该很小的半夜里波动。假设这个来源是一颗燃烧的星星，于是安排安装了一个高速探测器，以记录太阳耀斑的快速强度变化特征。1967年11月28日，这台记录仪揭示了一个惊人的事实，即该源正在以略大于1秒的间隔发射周期性的无线电噪声脉冲。此外，与地球时钟的比较表明，神秘的周期性信号保持时间的精度为百万分之一，并且爆发的持续时间很短，表明辐射源不可能比行星大得多。也许是因为像这样的天体很快就被解释为恒星脉动，它们被赋予了脉动射电源或脉冲星的有点误导性的名称，尽管我们现在知道它们的信号来自旋转，而不是周期性的膨胀和收缩，中子星。
The series of observations that eventually led to the unexpected discovery of the pulsating radio sources, or pulsars, began with Antony Hewish's pioneering studies of the twinkling of discrete radio sources caused by the motions of plasma clouds in the ionosphere and the solar corona. 1 As winds in the ionosphere blow clouds past the line of sight to a small radio source, the interference causes fluctuations in the received intensity with time scales of about 30 sec; similarly, the solar wind causes rapid fluctuations with time scales of a few tenths of a second. Hewish realized that observations of these fluctuations would provide a simple means of detecting compact radio sources. Moreover, because the distant radio galaxies and quasi-stellar objects have small angular dimensions, one method of acquiring quantitative information about the angular sizes of these sources is to study how their fluctuations change when they are observed at various angles in relation to the sun. Accordingly, Hewish and his colleagues constructed an array of 2,048 dipoles, which were spread over an area of 18,000 m2 to provide high sensitivity and which were operated at the long wavelength of 3.7 m, because the fluctuations were known to be more prominent at the longer wavelengths.By July 1967 the radio telescope was finished; a graduate student, Jocelyn Bell, was assigned the responsibility of using the instrument to obtain repeated observations of several radio sources at many different angles in relation to the sun. Bell diligently analyzed some 400 ft of chart recordings each week, and the radio sky was soon found to be heavily populated with compact sources. By the middle of August she had found a mysterious source that was fluctuating in the middle of the night when the effects of the solar wind should have been small. Under the assumption that this source was a flaring star, arrangements were made to install a high-speed detector to record the rapid intensity changes characteristic of solar flares. On November 28, 1967, this recorder revealed the astonishing fact that the source was emitting periodic bursts of radio noise at intervals just greater than 1 sec. Furthermore, comparisons with terrestrial clocks showed that the mysterious periodic signal kept time with an accuracy of 1 part in 1 million, and the short duration of the bursts suggested that the radiating source could not be much larger than a planet. Perhaps because objects such as this one were soon interpreted as stellar pulsations, they have been given the somewhat misleading name of pulsating radio sources, or pulsars, even though we now know that their signals come from the rotation, rather than the periodic expansion and contraction, of neutron stars.