The sun can be described as a yellow dwarf star, about 4.5 billion years old and halfway through its life cycle. Situated at the center of Earth's solar system, the sun is an almost spherical ball of hot plasma with a diameter approximately 109 times greater than Earth's. About 75 percent of the sun's mass is comprised of hydrogen, with the remainder of its mass consisting primarily of helium and much lesser quantities of heavier elements that include oxygen, carbon and iron.
Based on its spectral classification, the sun is a G-type main-sequence or GV2 star and accounts for approximately 99.86 percent of the mass present in Earth's solar system. The sun's core, which represents about 30 percent of its radius, comprises about 94 percent of its entire mass. The temperature at the center of the core is 27 million degrees Fahrenheit. By the time the heat carried by convection from the sun's core travels the distance to its surface, the temperature will have been reduced to 9,900 degrees F.
The sun produces its heat energy through a thermonuclear fusion process that converts hydrogen into helium. At its core, the sun fuses approximately 620 metric tons of hydrogen into helium each second. The heat generated at the sun's center takes about 170,000 years to reach its surface. When that energy is emitted from the sun's surface, it reaches Earth in about 8 seconds.