Collaborative Research: Development of a Green-Orange Astro-comb for Exoplanet and Cosmology Research

迄今为止，已经发现了400多颗系外行星的高色散光谱仪有一个共同的敏感性：需要超稳定、宽带、高线密度、明亮和连续的波长校准，以便能够在数周到数年的时间内精确地表征主星的小反射速度。这些研究的一项关键技术是利用锁模飞秒脉冲激光——它在频率空间中产生明亮的、有规则间隔的发射特征——与法布里-珀罗滤波腔一起产生适当的线密度，所有这些都锁定在原子钟上以保持长期稳定。这些所谓的“激光梳”具有使径向速度测量精度达到10厘米/秒的潜力；因此，确定类地系外行星的质量最终应该是可能的。哈佛-史密森天体物理中心的Ronald Walsworth和麻省理工学院的Franz Kaertner博士正计划为橙绿光谱建造这样一个激光梳，这个光谱区域非常适合探测类太阳恒星，因此也适合探测轨道周期为1年的行星存在于“生命区”的恒星，那里的地表水以液体形式存在。研究小组在这一领域有着出色的记录，他们开发了用于光学红色和蓝色光谱区域的激光梳。新梳子将在亚利桑那州霍普金斯山上的1.5米惠普尔天文台望远镜上进行测试，如果证明可靠，将应用于正在进行的一个项目，该项目是在Cerro Tololo美洲天文台的1.5米望远镜上进行的，该望远镜正在非常近的半人马座α / β恒星系统中寻找绕地外恒星。这项活动将涉及女性科学家和学生，由此产生的时间控制激光技术的应用应该远远超出天文学。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。

The high-dispersion optical spectrographs that have thus far enabled the discovery of more than 400 extrasolar planets have a common susceptibility: the need for ultrastable, broadband, high-line-density, bright, and continuous wavelength calibration so that the small reflex velocities of the host stars can be precisely characterized over periods of weeks to years. One crucial technology for these investigations utilizes a mode-locked femtosecond pulsed laser - which produces a bright, regularly spaced set of emission features in frequency space - together with a Fabry-Perot filtering cavity to create the appropriate line-density, all locked to an atomic clock for long-term stability. These so-called "laser combs" have the potential for enabling radial velocity measurements to a precision 10 cm/s; thus the determination of the mass of Earth-like exoplanets should eventually be possible.Dr. Ronald Walsworth of the Harvard-Smithsonian Center for Astrophysics and Dr. Franz Kaertner of the Massachusetts Institute of Technology are planning to construct such a laser comb for the orange-green spectrum, a region well-suited to the detection of solar-type stars and therefore of stars in which a planet with an orbital period of ~1 yr would exist in the "life-zone", where surface water would be in liquid form. The team of investigators has an excellent track record in this area, having developed laser combs for the optical red and blue spectral regions. The new comb will be tested at the 1.5-m Whipple Observatory telescope on Mt. Hopkins, Az, and, when proven reliable, applied to an ongoing project at the 1.5-m telescope at Cerro Tololo Interamerican Observatory that is searching for exo-Earths orbiting stars in the very nearby alpha/beta-Centaurus star system. The activity will involve both women as both scientists and students, and the resulting time-controlled laser technology should have application well beyond astronomy. Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.