Noun

Singular solar system

Plural solar systems

solar system (plural solar systems)

1. The Solar System; the Sun and all the objects in orbit around it.
2. Any collection of heavenly bodies including a star or binary star, and any lighter stars, brown dwarfs, planets, and other objects in orbit.
   • 1980, Carl Sagan, Cosmos: A Personal Voyage,

     The history of our study of our solar system shows us clearly that accepted and conventional ideas are often wrong, and that fundamental insights can arise from the most unexpected sources.

   • 1992, J. Laskar, page 31 in, Sylvio Ferraz-Mello (editor), "Chaos, resonance, and collective dynamical phenomena in the solar system", International Astronomical Union Symposium,

     I would like to stress out that the meaning of unstable for our solar system is very different than for another solar system.

   • 2001, Stuart Ross Taylor, Solar system evolution: a new perspective, 2nd edition, page xiii

     Every satellite has turned out to differ in some significant feature from its neighbor: " […] the sense of novelty would probably not have been greater if we had explored a different solar system".

The Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which were formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. Of the many objects that orbit the Sun, most of the mass is contained within eight relatively solitary planets whose orbits are almost circular and lie within a nearly flat disc called the ecliptic plane. The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, the gas giants, are substantially more massive than the terrestrials. The two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are composed largely of ices, such as water, ammonia and methane, and are often referred to separately as "ice giants".

The Solar System is also home to two regions populated by smaller objects. The asteroid belt, which lies between Mars and Jupiter, is similar to the terrestrial planets as it is composed mainly of rock and metal. Beyond Neptune's orbit lie trans-Neptunian objects composed mostly of ices such as water, ammonia and methane. Within these two regions, five individual objects, Ceres, Pluto, Haumea, Makemake and Eris, are recognized to be large enough to have been rounded by their own gravity, and are thus termed dwarf planets. In addition to thousands of small bodies in those two regions, various other small body populations, such as comets, centaurs and interplanetary dust, freely travel between regions.

The solar wind, a flow of plasma from the Sun, creates a bubble in the interstellar medium known as the heliosphere, which extends out to the edge of the scattered disc. The hypothetical Oort cloud, which acts as the source for long-period comets, may also exist at a distance roughly a thousand times further than the heliosphere.

Six of the planets and three of the dwarf planets are orbited by natural satellites, usually termed "moons" after Earth's Moon. Each of the outer planets is encircled by planetary rings of dust and other particles.