Abstract Details
| Name: Madhu Kashyap Jagadeesh Affiliation: Saint Joseph's University Conference ID: ASI2025_282 Title : (Re)-Defining Planets -- the Fundamental Planet Plane Authors and Co-Authors : Jagadeesh M. K., Arkil D.P., Safonova M. Abstract Type : Poster Abstract Category : Sun, Solar System, Exoplanets, and Astrobiology Abstract : More than 5500+ planets are detected using various techniques, with expectations of billions in our Galaxy alone. They are called super-earths, hot earths, mini-neptunes, hot neptunes, sub-neptunes, saturns, jupiters, hot jupiters, jovians, gas giants, ice giants, rocky, terran, subterran, superterran, … This prompted many recent works on taxonomy, or classification, of exoplanets. However, there is no basic, fundamental definition of `What is a planet?’, opposing to stars/asteroids/moons. Additionally, IAU 3rd law of planets states that a planet has to clear the neighbourhood around its orbit, which is still very difficult to determine even for closest exoplanets. The first ambitious task here is to establish if there is a limit on the size/mass of a planet. The lower mass limit may be assumed as of Mimas (0.03 EU) – ~min mass required to attain a nearly spherical hydrostatic equilibrium shape, following IAU 2nd law of planets. But the smallest exoplanet Kepler-37b is only 0.01 EU. The upper mass limit may be easier – there is a natural lower limit to what constitutes a star: ~0.08 SU. But then there are brown dwarfs: IAU has defined brown dwarfs as objects that exceed the deuterium burning limit (~13 JU), and giant exoplanets generally have masses of ~0.3 to ~60 JU. The resolution requires assembling the basic physical parameters that define planets quantitatively. Mass and radius are two fundamental properties and we propose a third correlated parameter: the moment of inertia. Based on these, we create the fundamental planet plane where, just like a galactic plane, the two parameters are correlated with the third. We propose to add the lower limit by plotting the moment of inertia versus log mass, where we are looking for a threshold or a turn-off point to define a planet. A fundamental planet plane will demonstrate the upper limit. |