Dr. Fischer will use the CHIRON spectrometer on the CTIO 1.5-m telescope to search for exoplanets via the radial velocity technique. She will target 30 bright late-type (G and K dwarf) stars with the goal of achieving 1 m/s measurement precision with new instrumentation after first testing it in a laboratory environment. The PI and her team will also develop a Doppler simulator to help determine the best possible observational precision.
This work will train postdoctoral research associates, graduate and undergraduate students in research and instrumentation. The team will also work on the ?jitter? observational problem, which results from vertical atmospheric motions on small spatial scales, and if solved, would have wide applicability to other fields of astronomy. They will also conduct a hands-on ?Pathways to Science? program for school children, and help the Yale planetarium director develop a new show on exoplanets.
The NSF-funded rocky planet search makes use of the CHIRON spectrograph, built by the Yale exoplanet lab and scientists at Cerro Tololo Interamerican Observatory (CTIO) for the 1.5-meter CTIO telescope. The goals of this project were to survey a set of 30 stars with high enough precision to detect low mass planets (a few to 40 times the mass of the Earth) with a particular focus on alpha Centauri A and B. to develop new technology to reach higher precision in our measurements to improve software for analyzing our data. We upgraded the CHIRON spectrograph to improve the stability and precision and are now obtaining very high precision velocity measurements of about 0.5 meters per second (the speed of a Giant Galapagos Tortoise) for the bright star tau Ceti (two months of data are shown in the attached Figure). To detect true analogs of Earth, we need to improve by another factor of five. However, we have unprecedented data sets for almost 30 bright stars now and analysis is continuing to decorrelate velocity sources from gas flow on the surface of the star with the dynamical motions induced by orbiting planets. One of the important things that we learned is that in addition to very high precision, we need almost nightly observations (sometimes several observations per night) to average over the stellar atmosphere velocities. This type of observing cadence is not possible for very large telescopes and is unprecedented even on small or moderate sized telescopes. To detect Earthlike planets, this research project shows that we need dedicated telescopes and additional technology development (in both hardware and analytical software techniques). Through work completed with this award, the CHIRON spectrometer is now a facility instrument, open to all astronomers (with time through SMARTS or NOAO). We developed a web-based interface to schedule observations and all calibrations. Users retrieve their raw and wavelength-calibrated extracted spectra from this web interface at the end of the night when their targets are observed. In the past, the telescope operators had to type in dozens of commands to a data-taking GUI interface and type in the star coordinates to point the telescope. Our web scheduling software generates a script so that the telescope operators simply click on "Start" or "Skip" and the data fields in the GUI are populated and coordinates are sent to the telesocpe. As a result, we have dramatically improved the efficiency of the telescope; we reduced typographical errors fro 40% to zero and recovered between 1 - 2 hours every night for observing. We obtained a very dense data set for alpha Centauri B. In a dedicated campaign in May 2013, we obtained more than 500 observations per night for 9 nights. This campaign was carried out in cooperation with a team of astronomers from Switzerland who were using the HARPS telescope on the neighboring mountaintop at La Silla Observatory. Both the Swiss team and our team are now developing new software to tease out the contamination of alpha Centauri A (alpha Cen A and B are orbiting each other and their projected separation is now small enough that light from the "A" star spills into our observations of "B"). We are working with applied mathematicians and statisticisans to optimize our analysis techniques and expect to complete analysis of this data set in the next year. The technology development associated with this project was used to educate, enlighten and train two university professors, two senior scientists, two postdoctoral fellows, two graduate students, three undergraduate students and one high school student (during a summer project).