Episode 351 - A new dwarf planet and what makes an exoplanet habitable

What makes a dwarf planet not a planet? What are the rules governing the word planet? Just how many dwarf planets are out there in our solar system? How can we use telescopes and modelling to add or subtract a dwarf planet from that list? We've talked about Goldilocks zone exoplanets, but what about their ability to withstand space weather? What role does a star's magnetic field play in protecting a planet from damaging radiation? Does space weather need to be added to the exoplanet Goldilocks zone? References: P. Vernazza, L. Jorda, P. Ševeček, M. Brož, M. Viikinkoski, J. Hanuš, B. Carry, A. Drouard, M. Ferrais, M. Marsset, F. Marchis, M. Birlan, E. Podlewska-Gaca, E. Jehin, P. Bartczak, G. Dudzinski, J. Berthier, J. Castillo-Rogez, F. Cipriani, F. Colas, F. DeMeo, C. Dumas, J. Durech, R. Fetick, T. Fusco, J. Grice, M. Kaasalainen, A. Kryszczynska, P. Lamy, H. Le Coroller, A. Marciniak, T. Michalowski, P. Michel, N. Rambaux, T. Santana-Ros, P. Tanga, F. Vachier, A. Vigan, O. Witasse, B. Yang, M. Gillon, Z. Benkhaldoun, R. Szakats, R. Hirsch, R. Duffard, A. Chapman, J. L. Maestre. A basin-free spherical shape as an outcome of a giant impact on asteroid Hygiea. Nature Astronomy, 2019; DOI: 10.1038/s41550-019-0915-8 Alison O. Farrish, David Alexander, Mei Maruo, Marc DeRosa, Frank Toffoletto, Anthony M. Sciola. Characterizing the Magnetic Environment of Exoplanet Stellar Systems. The Astrophysical Journal, 2019; 885 (1): 51 DOI: 10.3847/1538-4357/ab4652