As of late 2011, 702 exoplanets in 577 planetary systems and 82 multiple-planet systems have been identified  A substantial fraction of stars have planetary systems. Data from the HARPS mission indicates that this includes more than half of all Sun-like stars. Data from the Kepler mission has been used to estimate that there are at least 50 billion planets in our own galaxy. There also exist planetary-mass objects that orbit brown dwarfs and others that orbit the galaxy directly just as stars do, although it is unclear if either type should be labeled as a "planet".

As of early 2011, NASA's Kepler mission had identified 1,235 unconfirmed planetary candidates associated with 997 host stars, based on the first four months of data from the space-based telescope, including 54 that may be in the habitable zone. Six candidates in this zone were thought to be smaller than twice the size of Earth.

Planets are divided into two types: large, low-density gas giants, and smaller, rocky terrestrials. Under IAU definitions, there are eight planets in the Solar System. In order from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four gas giants, Jupiter, Saturn, Uranus, and Neptune. Many of these planets are orbited by one or more moons, which can be larger than small planets.

The Solar System also contains at least five dwarf planets: Ceres, Pluto (formerly considered to be the Solar System's ninth planet), Makemake, Haumea and Eris. No extrasolar dwarf planets have yet been detected.

Asteroids are small bodies circling the Sun, mostly in the Asteroid Belt between Mars and Jupiter. However, there are asteroids with orbits as small as Mercury and larger than Neptune. A number of other asteroids have been proposed as candidates for the dwarf planet category.

Trojans are small bodies that are in the same orbit as their host, either a planet or a moon. They sit at the stable Lagrangian points 60 degrees ahead and 60 degrees behind their host. Jupiter, Neptune, Mars, Earth, and some of Saturn's moons have Trojans. Earth's Trojan, 2010 TK7, was discovered by Martin Connors of Athabasca University in Alberta, Canada.

 

Other near earth objects (NEO's), besides 2010 TK7, are the asteroids 3753 Cruithne, 54509 YORP, 1998 UP1, 2002 AA29, and 2009BD which exist in resonant orbits.

Mars has four known co-orbital asteroids (5261 Eureka, 1999 UJ7, 1998 VF31, and 2007 NS2, all at the Lagrangian points), and Jupiter has many (more than 1000 known objects, the Trojan asteroids. 

Centaurs are asteroids, or minor planets, that have highly elliptical orbits, crossing the orbit of Neptune. These are also called Trans-Neptunian Objects (TNO's). Their orbits emanate inside the Kuiper Belt, scattered disc, and Oort Cloud, well beyond the orbit of Neptune. Their elleptic orbits can bring them as far as Jupiter before they return to their distant homes.

Comets are small asteroid-like bodies derived from the same source as Centaurs, but their orbits reach the inner Solar System. Energy from the Sun vaporizes some of the comet's material, giving the object a distinctive tail, or coma.

Moons orbit most Solar System planets except Mercury and Venus. Rings of dust and debris orbit all four gas giants. Shepard moons organize the rings into distinctive patterns, the most notable being Saturn's.