The solar system space contains the Sun and a vast array of orbiting objects including planets, moons, asteroids, comets, meteoroids, and interplanetary dust. These are bound to the Sun by gravity, which pulls them together in a circle around the star.
The process begins with an enormous cloud of gas and dust called a solar nebula, which gets larger and larger as it contracts and warms up. As material condenses and accretes it forms concentrations that eventually dominate areas of the solar nebula – they’re planetismals!
The Sun
The Sun is the bright star at the center of our solar system. It has been inspiring us since ancient times, and it is central to many world religions.
The solar system space is filled with a variety of planets, moons, asteroids, and comets. Astronomers have sent several spacecraft to investigate the Sun and other planets in the solar system.
The Sun is a luminous ball of plasma (hot gas) heated by nuclear fusion reactions in its core. It radiates this energy mainly as light, ultraviolet, and infrared radiation.
The Moon
The Moon is Earth’s natural satellite and the only planetary object that can be seen by the naked eye. It orbits Earth and is about one-fourth the size of our planet (a larger ratio than other natural satellites).
The Sun heats the Moon to a temperature of about 273 degrees F on its sunny side and minus 243 degrees F on its colder nightside. The Moon’s surface is rocky.
The Moon’s surface is pockmarked with craters created by the impact of meteoroids, asteroids and other small rocks. These impacts deposited a layer of debris called regolith on the lunar surface.
The Asteroids
The solar system space is filled with rocky bodies called asteroids, which range in size from a few meters to almost 1000 km across. Most asteroids revolve around the Sun in elliptical orbits.
Asteroids are composed of a mixture of sand, rock, and different metals including nickel and iron. They are characterized by their compositional differences, based on how far away from the Sun they formed.
There are three broad composition classes: C-types (chondrites), S-types, and M-types. The C-types are the most common and comprise about 75 percent of all known asteroids.
The Planets
The eight planets of our solar system, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, revolve around the Sun. The four inner planets, Earth, Venus and Mars, are terrestrial planets; the two largest, Jupiter and Saturn, are gas giants composed mainly of hydrogen and helium.
These giants are surrounded by a band of smaller, more icy objects known as the Kuiper belt, which extends beyond Neptune’s orbit. Some of the objects in the Kuiper belt are dwarf planets, such as Pluto.
All the natural satellites in our solar system, such as planets, dwarf planets, moons and asteroids, have been circling the Sun for billions of years. They were likely set in motion by the explosion of a star. They’re still moving today, a result of the forces of gravity, inertia, centripetal force and circular motion.
The Satellites
There are two types of satellites: Natural satellites and artificial. They are all orbiting around the sun in space, and they have a special job to do.
Many satellites orbit Earth in low-Earth orbit (LEO) at an altitude of 22,223 miles (36,000 km). These satellites are useful for communication, and they often work together as part of a large constellation to increase their coverage.
They also explore the solar system, looking for signs of water on Mars or capturing pictures of Saturn’s rings. They help scientists study space, which is very important to our planet’s future.