It has not been long since the only known planets resided in our solar system. Today, world-wide planet-finding efforts have identified over 400 planets orbiting more than 300 stars, and the contrast in properties between many of these systems and our solar system is challenging our understanding of planetary formation and evolution. The Holy Grail of planet-finding has always been to identify objects with near-Earth masses orbiting in the habitable zone of the host star. These planets offer the opportunity to search for evidence of life and thereby develop a better perspective on how it originated and flourished on Earth.
The detection of Earth-like planetary masses through the reflex motion of the host star requires either extremely high velocity precision measurements of moderate mass stars - beyond the capabilities of today's best instruments - or the study of low-mass main-sequence (i.e. M spectral type) stars. Because the latter are also very cool, they are faint and the target list is very short for optical studies even with the world's largest telescopes.
Dr. Suvrath Mahadevan at the Penn State University plans to upgrade an existing near-infrared laboratory spectrograph that has pioneered some of the techniques used in the above-mentioned discoveries and to apply that spectrograph at the Hobby-Eberly 9-m telescope toward the discovery of Earth-mass planets orbiting low-mass stars. In the near-IR, cool stars are bright and replete with narrow absorption features suitable for radial velocity analysis. Dr. Mahadevan is taking a reasonable and cost-effective approach by employing a sensitivity-cutoff detector array to greatly reduce the cooling requirements of the instrument and Fabry-Perot etalons and gas cells developed for the telecom industry to accomplish accurate wavelength calibration. Soon, this small but experienced group of scientists and students will bring a new instrument to make use of an important spectral region in the study of extrasolar planets. Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.
A major goal of this proposal was the acquisition and test of a 1.7 micron Hawaii-2RG detector and SIDECAR ASIC from Teledyne for the purpose of demonstrating its suitability for precision radial velocity surveys. This detector has been acquired and tested and will be the detector for the Habitable Zone planet finder, an NSF MRI funded NIR spectrograph The team also used the Pathfinder instrument with a laser frequency comb from NIST to obtain on-sky stellar spectrum with a comb as a calibration source, demonstrating the potential for a robust fiber-based laser comb. This has led to a new collaboration with NIST on developing laser combs for near-infrared astronomical applications. An FTS atlas of Uranium lines was produced to enable use of a Uranium-Neon hollow cathode lamp for calibration purposes. A new fiber-fabry perot based calibration source has also been developed using single mode fiber coated with dielectrics. These devices provide a compact, rugged, and stable grid of emission lines to help calibrate RV drifts of detectors. A commercial device was tested with the Sloan Digital Sky Survey (SDSS) APOGEE instrument as proof of concept and custom devices have been manufactured and tested as well. In addition to the technology development 15 refereed publications have been produced by work related to or inspired by this proposal, including interdisciplinary work on laser combs, and Habitable Zone boundaries of M dwarfs. Significant progress has also been made during this project towards enabling the goal of a ‘warm NIR spectrograph’, ie. using the cooled 1.7micron detector with suitable blocking glasses and filters to suppress thermal background to the levels where cooling of the instrument optics is no longer absolutely necessary. The goal is in sight and achievable with a 1.7 micron device using custom very high quality interference filters that we hope to test in the future. The broader impacts of this proposal are the development of new techniques and technology that will benefit the entire precision radial velocity community, an increased understanding of the insidious effects of stellar activity on M dwarf, and the training of graduate students and postdocs in aspects of instrumentation. As part of this proposal we also developed a demonstration on finding planets, infrared spectroscopy, Doppler radial velocity and bio-signatures, that has been used both at Penn State’s yearly Astrofest event as well as the US Science and technology Festival in Washington DC in 2012 and 2014. In addition team members have given public outreach talks in multiple venues.
