The Solar System
The solar system consists of the sun and everything that orbits around it. This includes the eight planets and their natural satellites (such as our moon), dwarf planets and their satellites, as well as asteroids, comets and countless particles of smaller debris.
It is our Sun and everything that travels around it. Our solar system is elliptical in shape. That means it is shaped like an egg. The Sun is in the center of the solar system. Our solar system is always in motion. Eight known planets and their moons, along with comets, asteroids, and other space objects orbit the Sun. The Sun is the biggest object in our solar system. It contains more than 99% of the solar system’s mass. Astronomers think the solar system is more than 4 billion years old.
Astronomers are now finding new objects far, far from the Sun which they call dwarf planets. Pluto, which was once called a planet, is now called a dwarf planet.
At the heart of the solar system is our sun. The four planets nearest it are rocky, terrestrial worlds — Mercury, Venus, Earth and Mars. After that are four gas giants — Jupiter, Saturn, Uranus and Neptune. Between the orbits of Mars and Jupiter lies the asteroid belt, which includes the dwarf planet Ceres. Beyond the orbit of Neptune one finds the disk-shaped
Kuiper belt, in which dwarf planet Pluto resides, and far beyond that is the giant, spherical Oort Cloud and the teardrop-shaped heliopause
Sun
The sun at the heart of our solar system is a yellow dwarf star, a hot ball of glowing gases. Its gravity holds the solar system together, keeping everything from the biggest planets to the smallest particles of debris in its orbit.
Size and Distance
With a radius of 432,168.6 miles (695,508 kilometers), our sun is not an especially large star — many are several times bigger — but it is still far more massive than our home planet: 332,946 Earths match the mass of the sun. The sun’s volume would need 1.3 million Earths to fill it.
The sun is 93 million miles (about 150,000,000 kilometers) from Earth. Its nearest stellar neighbor is the Alpha Centauri triple star system: Proxima Centauri is 2.24 light years away, and Alpha Centauri A and B — two stars orbiting each other — are 4.37 light years away. A light year is the distance light travels in one year, which is equal to 5,878,499,810,000 miles or 9,460,528,400,000 kilometers.
Structure
The sun, like others stars, is a ball of gas. In terms of the number of atoms, it is made of 91.0% hydrogen and 8.9% helium. By mass, the sun is about 70.6% hydrogen and 27.4% helium.
Moons
The sun doesn’t have any moons; instead, it has planets and their moons, along with asteroids, comets, and other objects.
Rings
The sun does not have rings.
Order of the Planets
The order of the planets from closest to the Sun outwards is; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and finally Neptune. The largest planet in the solar system is Jupiter, followed by Saturn, Uranus, Neptune, Earth, Venus, Mars with the smallest being Mercury.
Terrestrial Planets (Inner Planets)
The Terrestrial, or “rocky” planets in our solar system orbit relatively close to the Sun. There are four terrestrial planets: Mercury, Venus, Earth and Mars. They are made mostly of silicate rocks and metals, have solid surfaces, with atmospheres that range from very thick (on Venus) to very thin (on Mercury).
Of the four terrestrial planets, Earth and Mars are considered the most hospitable to life. Earth, of course, has life. Mars may have had life in the past, and it may exist there today. Conditions on Venus and Mercury are too extreme to have habitats that could nurture life.
Gas Giants (Outer Planets)
Gas giants are large planets that contain more than 10 times the mass of Earth. Their compositions are mostly gases, such as hydrogen, and small amounts of rocky material (mostly at their cores). The four gas giants in our solar system are Jupiter, Saturn, Uranus, and Neptune
Ice Giants
An ice giant planet is one that is at least ten times the mass of Earth, and contains a higher percentage of what planetary scientists refer to as “ices”. These are volatile elements heavier than hydrogen and helium, and were in ice form (mainly water) when the planets first formed. In our solar system, Uranus and Neptune are often referred to as “ice giants” due to the higher amounts of such volatile they contain. Astronomers have also determined that some exoplanets could be ice giants, as well.
Ring Systems
A ring system around a planet or asteroid is a disk made up of dust, chunks of material (ice, in the outer solar system), and small moons. This material forms a ring (or rings) around its parent body. The largest ring system in the solar system is the one around Saturn. Jupiter, Uranus and Neptune also have rings, and at least one asteroid is known to have a small ring as well.
