Collaborative Research: An Ultrastable Blue Astro Comb for Exoplanet and Cosmology Research

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Great progress has been made in recent years in detecting massive planets orbiting other stars. These exciting discoveries are an important step toward understanding the evolution of other solar systems and whether or not they may harbor life. Tantalizing as these discoveries are, however, they are not conclusive. Astronomers have yet to find a planet in another solar system that could support life as we know it. To do so would require finding smaller solid (not gaseous) earth-like planets orbiting a star within the "habitable zone" where the distance of the planet from the star is such that the surface temperature of the planet can sustain liquid water. There are at least four ways to detect a planet orbiting a star. By far the most successful means to date has been to very carefully monitor the velocity of the star. If the velocity tends to vary regularly about its average value, then it is possible that some celestial body is in orbit around it and we are measuring the reflex velocity of the star due to the changes in the position of the planet in its orbit. This is a very exacting measurement to make and it relies on extremely accurate velocity measurements made with a spectrograph. Large planets create the biggest velocity wiggle and are therefore easiest to detect. But detecting smaller earth like planets in the habitable zone requires much higher precision than is currently available. Dr. Franz Kaertner of the Massachusetts Institute of Technology is designing a very stable and accurate calibration mechanism to improve the radial velocity measurements. He is working with a number of scientific colleagues and several students to design and build the device over the next two years. This new scheme uses a very rapidly pulsed laser to imprint a regularly spaced calibration "comb" of lines of precisely known wavelengths through the spectrograph and onto the spectrum of the star. This new technique will improve the velocity determination from the current standard by about a factor of 100, enough to detect earth-like planets in the habitable zone.