Titius-Bode Relation, Timothy Bovaird, Charles H. Lineweaver, August 1, 2013 The Solar System and the Exoplanet Orbital Eccentricity - Multiplicity Relation, Mary Anne Limbach, Edwin L. Turner, April 9, 2014 The period ratio distribution of Kepler's candidate multiplanet systems, Jason H. Steffen, Jason A. Hwang, September 11, 2014 Are Planetary Systems Filled to Capacity? A Study Based on Kepler Results, Julia Fang, Jean-Luc Margot, February 28, 2013 Planet capture Free-floating planets in open clusters have similar velocities to the stars and so can be recaptured. They are typically captured into wide orbits between 100 and 105 AU. The capture efficiency decreases with increasing cluster size, and for a given cluster size it increases with the host/primary mass. It is almost independent of the planetary mass. Single and multiple planets could be captured into arbitrary unaligned orbits, non-coplanar with each other or with the stellar host spin, or pre-existing planetary system. Some planet–host metallicity correlation may still exist due to the common origin of the stars from the same cluster. Planets would be unlikely to be captured around neutron stars because these are likely to be ejected from the cluster by a pulsar kick when they form. Planets could even be captured around other planets to form free-floating planet binaries. After the cluster has dispersed some of the captured planets with orbits larger than 106 AU would be slowly disrupted by the galactic tide and likely become free-floating again through encounters with other field stars or giant molecular clouds. Zones Habitable zone The habitable zone around a star is the region where the temperature range allows for liquid water to exist on a planet; that is, not too close to the star for the water to evaporate and not too far away from the star for the water to freeze. The heat produced by stars varies depending on the size and age of the star; this means the habitable zone will also vary accordingly. Also, the atmospheric conditions on the planet influence the planet's ability to retain heat so that the location of the habitable zone is also specific to each type of planet. Habitable zones have usually been defined in terms of surface temperature; however, over half of Earth's biomass is from subsurface microbes, and temperature increases as depth underground increases, so the subsurface can be conducive for life when the surface is frozen; if this is considered, the habitable