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Our Solar System is technically the Sun and all of the objects that are attracted and held by the Sun’s gravity. This includes the eight planets and many other celestial objects. The eight planets in our Solar System are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
Mercury is the smallest planet in the Solar System. Because Mercury has almost no atmosphere, the planet experience radical shifts in temperature. Venus is known as the evening and morning star. It is a beautiful planet with a toxic atmosphere. Earth is the only planet that we know can support life. It is also the densest planet in the Solar System with a core comprised mostly of iron. Mars is a small planet compared to Earth. The planet’s red color is caused by the amount of iron oxide on its surface.
Between Mars and the outer planets is the asteroid belt, which is a large region filled with asteroids. The dwarf planet Ceres can also be found in this area.
Jupiter is by far the largest and most massive planet in our Solar System. A gas giant, it has no solid surface. Saturn is set apart by its incredible planetary ring system. Uranus is unique because it is the only planet in our Solar System to rotate on its side. Named after the Greek god of the sea, Neptune is blue due to the large amounts of methane in its atmosphere. Pluto is no longer the ninth planet due to a ruling by the International Astronomical Union (IAU). It is now classified as one of the dwarf planets.
Beyond the planets are more celestial objects and regions. The Trans-Neptunian region refers to the area beyond the orbit of Neptune. This large area is divided into different sections. The Kuiper Belt is a region that holds objects similar to the asteroid belt; however, these objects are composed mostly of ice. The scattered disc overlaps with the Kuiper Belt, but it goes much further out. Scientists think that short term comets come from the scattered disc. Eris, the dwarf planet that caused such an uproar, is in the scattered disc. Beyond the Kuiper Belt is also the hypothetical Oort Cloud.
The boundary between the edge of our Solar System and interstellar space is not clear. The boundary is determined by two things: solar wind and the Sun’s gravity. A boundary is formed when solar winds slow down to collide with the interstellar medium. However, that boundary is further muddied because the Sun’s gravity extends beyond that. Much of our Solar System is still unmapped.
Astronomy Cast has an episode on all of the planets in our Solar System as well as the outer Solar System.
NASA Solar System Exploration