Planetary migration occurs when a planet or other stellar satellite interacts with a disk of gas or planetesimals, resulting in the alteration of the satellite’s orbital parameters, especially its semi-major axis.
A comet is an icy small Solar System body that, when passing close to the Sun, heats up and begins to outgas, displaying a visible atmosphere or coma, and sometimes also a tail.
The Earth Similarity Index (ESI) is a proposed characterization of how similar a planetary-mass object or natural satellite is to Earth. It was designed to be a scale from 0.0 to 1.0, with Earth having a value of 1.0; this is meant to simplify planet comparisons from large databases.
The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly.
A debris disk is a circumstellar disk of dust and debris in orbit around a star. Debris disks have been found around both mature and young stars, as well as at least one debris disk in orbit around an evolved neutron star.