Solar System 101 | National Geographic
– Our solar system is oneof over 500 known solar systemsin the entire Milky Way galaxy. The solar system came into beingabout 4. 5 billion years ago, when a cloudof interstellar gas and dust collapsed,resulting in a solarnebula, a swirling discof material that collidedto form the solar system. The solar system is locatedin the Milky Way’s Orion star cluster. Only 15% of stars in thegalaxy host planetary systems,and one of those stars is our own sun. Revolving around thesun are eight planets. The planets are dividedinto two categories,based on their composition,Terrestrial and Jovian. Terrestrial planets includingMercury, Venus, Earth,and Mars, are primarilymade of rocky material. Their surfaces are solid,they don’t have ring systems,they have very few or no moons,and they are relatively small. The smallest and closestto the sun is Mercury,which has the shortestorbit in the solar systemat about three Earth months. Venus is the hottestplanet, with temperaturesof up to 867 degreesFahrenheit, due to an atmosphereof carbon dioxide andextensive lava flows. Next to this world of fireis a world of water, Earth. The water systems onthis planet help createthe only known environment in the universecapable of sustaining life. The last of the terrestrial planets, Mars,might have also supported lifeabout 3. 7 billion years ago,when the planet had a waterysurface, and moist atmosphere. Beyond the four Terrestrial planetsof the inner solar systemlie the Jovian planetsof the outer solar system. The Jovian planets includegas giants Jupiter and Saturnand ice giants Uranus and Neptune. The gas giants arepredominantly made of heliumand hydrogen, and the icegiants also contain rock, ice,and a liquid mixture ofwater, methane, and ammonia. All four Jovian planetshave multiple moons,sport ring systems, have nosolid surface, and are immense. The largest Jovian isalso the largest planetin the solar system, Jupiter. Nearby is Saturn, the solarsystem’s second largest planet. Its signature rings are wide enoughto fit between Earth and the moon,but are barely a kilometer thick. Past Saturn are the icegiants, Uranus and Neptune. The slightly bigger ofthese ice giants, Uranus,is famous for rotating on its side. Next to Uranus is Neptune,the outermost planetin the solar system, andalso one of the coldest. Orbiting the Terrestrialplanets is the asteroid belt,a flat disc of rockyobjects, full of remnantsfrom the solar system’s formation. From microscopic dust particles,to the largest known object,the dwarf planet, Ceres. Another disc of space debrislies much further out,and orbits the Jovianplanets, the icy Kuiper Belt. Apart from asteroids, theKuiper Belt is also hometo dwarf planets, such as Pluto,and is the birthplace of many comets. Beyond the Kuiper Belt is the Oort Cloud,a vast, sphericalcollection of icy debris. It is considered theedge of the solar systemsince that is where the gravitationaland physical influences of the sun end. Our solar system’sparticular configurationof planets and other celestial objects,all revolving around a life-giving star,make it a special place to call home.