The Great Nebula in Orion also known as M42 is in the middle of Orion’s sword. It is roughly 1500 light years away and close to 30 light years across. The red color is primarily ionized hydrogen gas and the blue is either helium gas or dust. The four bright stars in the core are lighting up the cloud with intense radiation that cause the gas around them to ionize and glow. The four stars are type O stars and measure about 40,000 to 60,000 degrees Kelvin. These stars typically live about 100 million years as opposed to our suns 10 billion year life span.