The Aurora lights up the frigid night sky. Also known as the northern lights (aurora borealis) or southern lights (aurora australis), the Aurora is a breathtaking natural phenomenon. Auroras are caused by energized particles from the sun slamming into Earth's upper atmosphere at crazy speeds (72 million km/h). Earth’s magnetic field then redirects the particles toward the north and south poles. The electrically charged particles then enter Earth's atmosphere, exciting gas atoms and molecules and generating auroras. The colour of auroras depends on the gas mixture in the atmosphere. The most common Aurora colour green, is caused from oxygen particles. Blue and purple colours are produced by nitrogen.