The Mass Function and Galactic Distribution of Cool Planets from Microlensing

Ohio State University, The, Columbus OH

Investigators

Abstract

Searches for planets orbiting other stars (exoplanets) have discovered thousands of planetary systems orbiting a wide variety of stars. Most of these surveys are only able to detect planets on relatively small orbits similar to that of Jupiter or smaller. Furthermore, the vast majority of the stars so far known to host planets are relatively close to the Sun. Therefore, little is known about the outer regions of planetary systems, and almost nothing is known about the distribution of planets farther away in the galaxy. Microlensing, which occurs when a distant star gets sufficiently aligned with a massive compact foreground object to bend its light due to its gravitational field, resulting in an observable magnification, can address this. Microlensing surveys for exoplanets, on the other hand, are sensitive to cool, low-mass planets in the outer parts of solar systems. Furthermore, microlensing is sensitive to planets in a range of environments in our Milky Way galaxy. It is perhaps the only way to detect whether free-floating planets exist. This team will develop microlensing methods and use them to determine the properties and Galactic distribution of planets that do not orbit close to a host star. This work relies on observations from the amateur astronomy community, and this team will organize an international workshop to bring the amateur and professional communities together. This program is a combination of theoretical and observational work to develop methods to measure the mass and distance to a large and broad sample of microlens planets. The CoPIs and their students will: 1) Develop methods to measure the microlens parallax effect, which provides the most robust way to measure the mass of and distance to microlenses. Using the results from two Spitzer campaigns totalling over 900 hours, they will study the phenomenology of all types of microlens parallaxes measurement methods. (2) Develop a unified, comprehensive understanding of the microlens parallax effect. This synthesis of various methods will enable parallax measurements, and thus mass and distance estimates, for a large and broad sample of planetary systems. (3) Continue to lead the Microlensing Follow Up Network effort to find extra-solar planets by monitoring high-magnification microlensing events.