The Sun and all the planets lie approximately on the same plane. This suggests that the solar system formed from a disc of material that was in orbit around the Sun. By definition the ecliptic plane contains the Earth’s orbit. The angle of other planet’s orbits relative to this is called their inclination, e.g. Mars has an inclination of 1.8 degrees. Mercury’s inclination is greatest of all the planets at 7 degrees. The Astronomical Unit (AU) What units we use to measure a distance depends…Continue Reading “The Earth in Orbit”

The Sun Our Sun is a star, a huge ball of Hydrogen and Helium with a nuclear reaction, fusion, happening in its core. It formed from a cloud of Hydrogen billions of years ago and when it formed a number of objects were formed too or relatively shortly after. These objects make up what we call our solar system. Planets and Dwarf Planets Planets According to the International Astronomical Union a planet is an object which: Is in orbit around the Sun Has a mass…Continue Reading “What’s in the Solar System?”