The Solar System 2014

Birth Formed 4.5 billion years ago from remains of an ancient super nova. This exploded star left clouds of gas and dust that are called a stellar nebula. Our Sun was created from these huge clouds of gas and dust. There were many small and large rocks that gradually came together because of gravity and formed the planets, moons, asteroids, and comets. Many of the craters which can be found on the Moon were made when these rocks came crashing on to the surface.  

Our Solar System

There are at least thirteen planets (or planet-like objects)in our solar system. Mercury is 58,000,000-km from the sun. Pluto is 5,913,000,000-km from the sun. These numbers are hard to use!

Astronomical Units We will use AU’s to measure distances in the solar system. The Earth is about 150,000,000-km (93,000,000 miles) on average from the sun. So we will call this distance 1 AU.

Planetary Distances Mercury 0.4 AU Venus 0.7 AU Earth 1.0 AU Mars 1.5 AU Jupiter 5.0 AU Saturn 10.0 AU Uranus 19.0 AU Neptune 30.0 AU Pluto 39.0 AU Light travels through space at 300,000-km/s. So it takes about 8 minutes for light from the sun to travel 1 AU and reach us. How long would it take light from the sun to reach Pluto? 39 x 8 = 312 minutes, or 5.2 hours!

Mass of the Solar System Almost all the mass in our solar system is in the sun. Mass of the Solar System Sun 99.80% Jupiter 0.10% Comets 0.05% Other 8 planets 0.04% Total of Sun + Planets + Comets = 99.99%

Our Sun Is just a medium sized star (yellow dwarf). It is about 1.4 million kilometers in diameter It would take 10 Jupiter’s or 109 Earths to fit across the Sun! Makes life on our planet possible by giving us great amounts of light and heat by nuclear fusion. Made of hydrogen (75%) and helium (25%) 4.5 billion years old, with fuel for another 5 billion years or so.

Planetary Zones First Zone: Contains the rocky terrestrial planets Mercury to Mars. Asteroid belt divides the first and second zones. Second Zone: Contains the gas giants Jupiter through Neptune. Third Zone: Goes from the orbit of Neptune out to 50 AU. Includes Pluto and the “ice dwarfs” in the Kuiper Belt.

The Inner Planets/1st Zone Planets are rocky. Called terrestrial from the Latin word terra, which means Earth. They are all small, and closer to the Sun. Few moons Closely spaced

Outer Planets/2nd Zone Separated from the 1st zone by the asteroid belt, the 2nd Zone contains the gas giants. Made of Hydrogen and Helium Very large Not believed to have solid surfaces. Have rings and many moons. Really far apart

Gas Giants Atmospheres Since they have so much mass, their strong gravity can keep even light gases from escaping. Atmosphere tends to resemble the sun (75% H, 24% He, 1% other gases). No well defined surface. Liquid oceans of hydrogen or water might exist. Gases just get denser and denser as you go deeper. Might become liquid metallic hydrogen, which has properties of liquids and metals. Exist only under high pressure. Causes Jupiter's magnetic field.

Gas Giants Cores Gas giants are believed to have solid cores made of rock,, ice, frozen carbon dioxide, and other compounds. Cores would be several times the size of the Earth.

Dwarf Planets Planets must: Be in orbit around Sun. Have enough mass so gravity makes them round. Have cleared their orbit of similar objects. If they don’t meet this criteria, they are considered to be dwarf planets. Today we know of five: Pluto, Ceres, Eris, Haumea, and Makemake. There are many more in the Kuiper Belt. Except for Ceres, all are in the Kuiper Belt. Not all astronomers are happy with the whole dwarf planet thing.

Left Overs Comets are chunks of water ice, frozen gases, and dust whose orbits are very long, narrow ellipses. Often thought of as dirty snowballs. Asteroids are small rock and metal pieces left over form the formation of planets. Meteoroids are smaller pieces of rock and metal also left over from the formation of our Solar System. Meteoroids become meteors in our atmosphere, and meteorite on the ground