About Me
I am the star at the center of your solar system. The Earth and other matter (including other planets, asteroids, meteoroids, comets and dust) orbit me, which by myself, I account for more than 99% of the solar system's mass. Energy from me—in the form of sunlight, support almost all life on Earth via photosynthesis, and, via heating from insolation—drive the Earth's climate and weather.
About 74% of the my mass is hydrogen, 25% is helium, and the rest is made up of trace quantities of heavier elements. I am about 4.6 billion years old and about halfway through my main-sequence evolution, during which nuclear fusion reactions in my core fuse hydrogen into helium. Each second, more than 4 million tonnes of matter are converted into energy within my core, producing neutrinos and solar radiation. In about 5 billion years, I will evolve into a red giant and then a white dwarf, creating a planetary nebula in the process.
I am a magnetically active star; support a strong, changing magnetic field that varies year-to-year and reverses direction about every eleven years. My magnetic field gives rise to many effects that are collectively called solar activity, including sunspots on the surface of the Sun, solar flares, and variations in the solar wind that carry material through the solar system. The effects of solar activity on Earth include auroras at moderate to high latitudes, and the disruption of radio communications and electric power. Solar activity is thought to have played a large role in the formation and evolution of the solar system, and strongly affects the structure of Earth's outer atmosphere.
Although I am the nearest star to Earth and have been intensively studied by scientists, many questions about me remain unanswered, such as why my outer atmosphere has a temperature of over a million K while my visible surface (the photosphere) has a temperature of just 6,000 K. Current topics of scientific enquiry include my regular cycle of sunspot activity, the physics and origin of solar flares and prominences, the magnetic interaction between the chromosphere and the corona, and the origin of the solar wind.
