Three Body Dynamics
Three-body dynamics in the hierarchical limit, where one of the objects is far away from the others, shows interesting properties. For instance, the closely separated two objects can be flipped and move even closer to each other, due to perturbations from a near co-planar more distant object (Li et al. 2014a, Li et al. 2014b). This has wide applications in astrophysical systems, such as the formation of misaligned hot Jupiters (e.g., Li et al. 2014a), the enhanced tidal disruptions rates around supermassive BH binaries (e.g., Li et al. 2015).
Dynamical Origin and Habitability of Extrasolar Planets
The recently discovered exoplanetary systems exhibit numerous puzzling features, many of which cannot be explained by traditional planet formation theory. In particular, in contrast with our own solar system, where the angle between the spin of the Sun and the planetary orbits is small (~ 7o), the discovered exoplanetary systems exhibit large misalignments. This challenges the classical planet formation theory, and the spin-orbit misalignment can in turn be used as a key constraint on planetary formation mechanism (e.g., Li et al. 2014a, Li & Winn 2016, Li et al. 2020, Chen et al. 2022). In addition to spin-orbit misalignment, my team uses observed Tatooine worlds (planets orbiting around stellar binaries) to constrain planetary formation (Li et al. 2016, Hong et al. 2019).
Are we alone in the universe? This is an age-old question that has constantly piqued the interest of mankind. Thanks to the thousands of exoplanets – planets outside the Solar System – that have been discovered over the past decade, we are more empowered than ever to answer this fundamental question. To better predict the habitability of these exoplanets, my team extends the study on the spin axis variations of our own Earth, and quantify the changes in the spin-axis orientation of exoplanets (Li & Batygin 2014a, Li & Batygin 2014b, Shan & Li 2018, Li et al. 2021). Large variations of the spin-axis can lead to snowball transitions of the planets (Quarles et al. 2021).
Distant Solar System
In the vast outskirts of the Solar System beyond Neptune reside the minor planets known as trans-Neptunian objects (TNOs). Detailed analysis of their orbital architecture reveals unexpected features, challenging our understanding of the way in which the outer Solar System works, and hinting at the possibility of outer planets, which are too faint to yet be detected. These discoveries motivate the study of the dynamical processes in the outer solar system which govern TNO orbits. Understanding the ongoing dynamical processes which shape the orbits of TNOs will constrain any undetected planets and facilitate their detection (e.g., Li et al. 2018, Bhaskar et al. 2020) and probe the formation history of our own Solar System (Li & Adams 2016, Moore et al. 2020).
Stars in Galactic Nuclei
Super massive black hole binaries are natural consequences of galaxy mergers, and the merge of SMBHBs can produce gravitational waves (GWs). Electromagnetic counterparts of GWs provide valuable information on the host galaxy redshift and the environment of the GW sources. To this end, my team investigated the electromagnetic (EM) counterpart of gravitational waves emitted by a SMBHB through the viscous dissipation of the GW energy in an accretion disk and stars surrounding the SMBHB (Li et al. 2013). In addition, we charactered tidal disruption rate enhancement for stars around SMBHBs (Li et al. 2015).
Dynamics of Merging Compact Binaries
The detection of gravitational waves have generated renewed interest in understanding the formation and evolution of compact binaries. Many formation channels have been proposed to explain the origin of the binaries. However, questions remain open to distinguish the different formation channels, to explain the observed puzzles and to make predictions for future observations. To this end, our group explore the dynamical evolution of the gravitational wave sources of compact binaries, including those in the AGN disk (Bhaskar et al. 2022, Li et al. 2022, Bhaskar et al. 2023). We investigate how the secular dynamical resonance influence the merger properties, which leave imprints in the gravitational wave signatures and can in turn help distinguish the different formation channels.
I’m fortunate to work with talented Georgia Tech undergraduate students, graduate students and postdocs (first row from left to right: Renyi Chen, Gongjie Li, Lee Hassenzahl, Karthik Yadavalli, second row from left to right: Nathan Moore, Billy Quarles, Chen Chen, Hareesh Bhaskar, Yash Tomar).