THE Solar System

The solar system includes the Sun and all the objects that orbit around it due to its gravity. This includes things such asplanets, comets, asteroids, meteoroids and moons. The Solar System formed around 4.6 billion years ago. There are eight planets in the Solar System. The four inner planets are Mercury, Venus, Earth and Mars while the four outer planets are Jupiter, Saturn, Uranus and Neptune. The inner planets (also known as terrestrial planets) are smaller and made mostly of rock and metal. The outer planets (also known as gas giants) are much larger and made mostly of hydrogen, helium and other gases. As of 2008, there are also five dwarf planets: Pluto, Ceres, Eris, Makemake & Haumea. There is an asteroid belt which lies between the orbits or Mars and Jupiter, it features a large number of irregular shaped asteroids. For thousands of years humans were unaware of the Solar System and believed that Earth was at the center of the Universe. Astronomers such as Nicolaus Copernicus, Galileo Galilei, Johannes Kepler and Isaac Newton helped develop a new model that explained the movement of the planets with the Sun at the center of the Solar System. The Sun contains 99.86 percent of the Solar System's known mass, with Jupiter and Saturn making up making up most of the rest. The small inner planets which include Mercury, Venus, Earth and Mars make up a very small percentage of the Solar System’s mass.

Comets

Enjoy these fun comet facts for kids. Learn interesting info about Halley’s Comet, Shoemaker-Levy 9 (the comet that collided with Jupiter in 1994), what comets are made of, why they have tails and lots more.

A comet is a relatively small solar system body that orbits the Sun. When close enough to the Sun they display a visible coma (a fuzzy outline or atmosphere due to solar radiation) and sometimes a tail. The coma is created as the comet gets closer to the Sun, causing water, carbon dioxide and other compounds to sublime (quickly changing from solid to gas) from its surface. Comets are made of ice, dust and small rocky particles. The name comet comes from the Greek word meaning ‘hair of the head’, it came from the Greek philosopher Aristotle who observed comets as ‘stars with hair’. Short term comets (also known as periodic comets) have orbital periods of less than 200 years while long term comets have orbital periods of over 200 years. Halley's Comet Halley’s Comet (or Comet Halley as it is also known) is the most well known comet. It is known as a periodic comet (or short term comet) because the time it takes to orbit the Sun is less than 200 years. Records of humans observing Halley’s Comet go back thousands of years, with appearances noted by Babylonian, Chinese and European star gazers. It can be seen with the naked eye from Earth every 75 to 76 years (although the time period has between 74 and 79 years in the past). It last appeared in the inner Solar System in 1986 and will return again sometime in 2061 (start charging your camera battery). Halley’s Comet is named after English astronomer Edmond Halley who first determined its period of orbit. It was the first comet to be recognized as having a periodic orbit. Halley’s Comet appearance in 1986 allowed researchers to investigate its make up more closely using spacecraft. While some previous theories were proven correct, other models were altered with the new information. For example, while earlier models predicted the comet to feature many volatile ices, the actual amount was less than first expected. The tail and fuzzy glow you see around Halley’s Comet is known as a coma. It occurs when the comet gets close to the Sun and compounds such as frozen water and carbon dioxide sublime (rapidly change from solid to gas) from its surface. While the coma over Halley’s Comet can stretch up to 100,000 km across, the nucleus is actually small, only around 15km (9.3 miles) long, 8km (5 miles) wide and 8km (5 miles) thick. Comet Shoemaker-Levy 9 In July 1994, the Shoemaker-Levy 9 comet broke apart and collided with Jupiter. This event gave astronomers a unique opportunity to observe what happens when such a collision occurs. The largest fragments were 2 km (1.2 mi) in diameter and struck Jupiter at a speed of around 60 km/s (37 mi/s). The impact scars were clearly visible for months after the impact. Shoemaker-Levy 9 was originally located by astronomers Eugene M. and Carolyn Shoemaker and David Levy in March 1993.

The Sun

Enjoy these fun Sun facts for kids. Learn how hot the Sun is, how long it takes light from the Sun to reach Earth, what the Sun is made of and more. Read on for a range of interesting facts about the Sun.

The Sun is a star found at the center of the Solar System. It makes up around 99.86% of the Solar System’s mass. At around 1,392,000 kilometres (865,000 miles) wide, the Sun’s diameter is about 110 times wider than Earth’s. Around 74% of the Sun’s mass is made up of hydrogen. Helium makes up around 24% while heavier elements such as oxygen, carbon, iron and neon make up the remaining percentage. Light from the Sun reaches Earth in around 8 minutes. The Sun’s surface temperature is around 5500 degrees Celsius (9941 degrees Fahrenheit), so pack plenty of sunscreen if you plan on visiting (remembering that the average distance from the Sun to the Earth is around 150 million kilometers). The Sun’s core is around 13600000 degrees Celsius! The Sun generates huge amounts of energy by combining hydrogen nuclei into helium. This process is called nuclear fusion. Because of the Sun’s huge influence on Earth, many early cultures saw the Sun as a deity or god. For example, Ancient Egyptians had a sun god called Ra while in Aztec mythology there is a sun god named Tonatiuh. The Sun produces a solar wind which contains charged particles such as electrons and protons. They escape the Sun’s intense gravity because of their high kinetic energy and the high temperature of the Sun’s corona (a type of plasma atmosphere that extends into space). Planets with strong magnetic fields such as Earth manage to deflect most of these charged particles as they approach. A solar eclipse occurs when the Moon is between the Sun and the Earth.