MRI: Acquisition of a Stable Hydrogen Maser Frequency Standard for mm/submm VLBI Observations of a Black Hole Event Horizon

MRI：获取黑洞视界毫米/亚毫米 VLBI 观测的稳定氢脉泽频率标准

• 批准号: 0922984
• 负责人: Sheperd Doeleman
• 金额: $ 28.79万
• 依托单位: Northeast Radio Observatory Corp
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-15 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0922984&HistoricalAwards=false
• 关键词: MRI; Acquisition; Stable; Hydrogen; Maser

The ability of astronomers to detect fine structure details in distant objects depends upon the angular resolution obtainable from their telescopes and instruments. Angular resolution is related to the wavelength at which the observations are made (the smaller the wavelength, the higher the resolution that can be achieved) and also to the diameter of the observing objective (the larger the objective, the higher the resolution). In most cases the observing objective is the size of the telescope's primary mirror. But when multiple telescopes are used simultaneously and their beams are combined the objective size becomes the baseline distance between the telescopes used. For several decades, radio astronomers have taken advantage of large baselines by coordinating observations between radio telescopes on different continents in a technique termed Very Long Baseline Interferometry (VLBI). This technique has enabled radio astronomers (who work at quite long wavelengths compared to that of visual light) to achieve angular resolutions that rival, and in some cases surpass, the kinds of resolutions available to optical astronomers. Now Dr. Sheperd Doeleman of the MIT Haystack Observatory wants to obtain even higher resolution by moving VLBI observations to shorter wavelengths. His idea will be made possible, in part, through an award from the National Science Foundation's Major Research Instrumentation program that will enable him to obtain a very stable high frequency standard that is necessary to calibrate the observations at the shorter wavelengths. This new standard will enable observations that will lead to a better understanding of the environment surrounding the Black Hole at the center of our Milky Way Galaxy, more than 20,000 light years away.

天文学家探测遥远天体精细结构细节的能力取决于他们的望远镜和仪器所能获得的角度分辨率。角分辨率与观测的波长有关（波长越小，分辨率越高），也与观测物镜的直径有关（物镜越大，分辨率越高）。在大多数情况下，观测物镜是望远镜主镜的大小。但是，当多个望远镜同时使用并且它们的光束组合在一起时，物镜尺寸就成为所使用的望远镜之间的基线距离。几十年来，射电天文学家利用一种称为甚长基线干涉测量（VLBI）的技术，在不同大陆的射电望远镜之间协调观测，从而利用了大基线。这项技术使射电天文学家（与可见光相比，射电天文学家工作的波长相当长）能够获得与光学天文学家所能获得的分辨率相媲美的角分辨率，在某些情况下甚至超过了这种分辨率。现在，麻省理工学院干草堆天文台的谢珀德·多尔曼博士希望通过将VLBI观测移动到更短的波长来获得更高的分辨率。他的想法将成为可能，部分原因是由于国家科学基金会的主要研究仪器项目的奖励，这将使他能够获得一个非常稳定的高频标准，这是校准短波长的观测所必需的。这个新标准将使观测能够更好地了解银河系中心黑洞周围的环境，距离我们超过2万光年。