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
09/05/2016
Move over Hubble -- here comes the James Webb Space Telescope (JWST). JWST promises to be the new most powerful telescope in space. In the last month, the 18-segment gold-plated primary mirror for JWST was unveiled. In the featured time-lapse video taken last week, the 6.5-meter diameter mirror was raised to a vertical position. The dramatic 30-second sequence shows NASA engineers monitoring the test as room lights glint brightly off the mirror's highly reflective surface. The beryllium mirrors have been coated with a thin film of gold to make them more reflective to infrared light. The science goals of JWST include studying the workings of the early universe and the properties of planets orbiting nearby stars. Because of the mirror's great size, it will be folded for launch and then, assuming all goes as planned, dramatically unfolded again in space. The JWST, a joint mission of the space agencies of the USA, Europe, and Canada, is currently scheduled to be launched in late 2018. NASA Coverage: Today's Transit of Mercury across the Sun