The Sun
The Sun is a yellow dwarf star (G2V), about 4.6 billion years old, and the dominant gravitational force in the Solar System. It has a diameter of roughly 1.4 million kilometers and contains around 99.8% of the Solar System’s mass. Nuclear fusion in its core converts hydrogen into helium, producing energy that warms the planets. Above the core lie the radiative and convective zones, followed by the visible photosphere (~5,500 °C), the chromosphere, and the much hotter corona (~2 million °C).
Source: science.nasa.gov
APODs including "The Sun"
A Mirry Christmas Credit:
24/12/1996
Thinking about spending the Holiday Season in low Earth orbit? Astronaut John Blaha and his cosmonaut colleagues Valeri Korzun and Alexander Kaleri are doing just that onboard the Russian Mir spacestation. You can e-mail them Seasons Greetings. Blaha replaced Shanon Lucid as a Mir resident during the STS-79 mission flown by the Space Shuttle Atlantis and is scheduled to be replaced by Jerry Linenger when Atlantis makes another shuttle run to Mir during the STS-81 mission. The Mir is seen here 200 miles above the Earth as the sun sets following the latest Atlantis undocking. NASA shuttle flights to the Mir are part of the Phase 1 program for construction of the International Space Station.