Collaborative Research: Infrared RV Planet Search with Externally Dispersed Interferometry II: Optimization

天文学家们用来寻找行星的最有效的方法之一是，当行星在其轨道上围绕恒星运行时，试图探测恒星的速度变化。这种经过验证的技术使用一种叫做摄谱仪的仪器来测量恒星光谱中特征波长的微小变化。这种变化是由于我们熟悉的多普勒效应造成的，并且可以直接与恒星速度的变化有关。但是这些速度变化非常小，为了精确地测量它们，有必要采用一些方案来校准光谱仪中的光的波长。一项相对较新的技术是使用干涉测量法，测量两束光在一起时的“干涉”。在一个特定的波长，两束光将导致条纹的出现，这些条纹是根据它们的波长间隔的。通过测量这些条纹的间距，可以非常精确地确定波长。加州大学伯克利分校的杰里·埃德尔斯坦博士和康奈尔大学的詹姆斯·劳埃德博士正在将这项技术应用于一种摄谱仪，这种摄谱仪不是在可见光下工作，而是在红外线下工作。红外光在研究较冷和较小的恒星时非常有用，这些恒星比热恒星数量更多。在这些恒星周围找到行星将给我们一个比我们目前所知道的行星是如何形成和演化的更清晰的画面。由于这些恒星比那些经常被研究的大质量热恒星更冷，它们的宜居带，即离恒星较远的区域，那里的条件可能适合生命的开始，离母星更近。迄今为止发现的大多数行星都是像木星这样的“气态巨行星”，它们离恒星太远，我们所知道的生物不可能存在。但有了这个新仪器，可能会在冷恒星的可居住区域发现更小的类地行星。这项工作的资金由美国国家科学基金会天文科学部通过其先进技术和仪器项目提供。

One of the most effective means employed by astronomers to search for planets around stars other than our sun is to try to detect the velocity shift of the star as the planet moves about the star in its orbit. This well proven technique employs an instrument called a spectrograph to measure the small shifts in wavelength of features in a star's spectrum. The shifts are due to the familiar Doppler effect and can be directly related to the changes in the star's velocity. But these velocity shifts are very small, and in order to measure them with great accuracy it is necessary to employ some scheme to calibrate the wavelength of the light in the spectrograph. One relatively new technique is to use interferometry, measuring the "interference" of two beams of light when they come together. At a particular wavelength, the two beams of light will cause fringes to appear which are spaced according to their wavelengths. By measuring the spacing of these fringes, wavelengths can be determined very accurately. Dr. Jerry Edelstein of the University of California-Berkeley and Dr. James Lloyd of Cornell University are applying this technique to a spectrograph that works not in visual light, but in the infrared. Infrared light is very useful in the study of cooler and smaller stars which are more numerous than hot stars. Finding planets around these stars will give us a much clearer picture than we currently have of how planets are actually formed and evolve. Since these stars are cooler than the massive hot stars that have been most frequently studied, their habitable zones, the region at the distance from the star where conditions may be suitable for life to begin, are much closer to the parent star. Most of the planets discovered so far have been "gas giants" like Jupiter and are located too far from their star for biology as we know it to exist. But with this new instrument, smaller earth-like planets may be detected in the habitable zone of cool stars. Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.