The Sun

Some basic information, and how we get it:

• Distance: 1 AU ~ 150 x 10⁶ km.
• Size: radius ~ 0.7 x 10⁶ km.
• Mass: ~ 2 x 10³⁰ kg.
• Density: ~ 1400 kg/m³.
• Temperature: at photosphere ~ 6000 K.
• Luminosity: ~ 4 x 10²⁶ W.
• Composition: 74% H, 25% He, 1% other (by mass).

The layer of the Sun that we see is the photosphere.

The photosphere often contains sunspots.

The Sun has a 22 year cycle.

The chromosphere lies above the photosphere.

The corona lies above the chromosphere extends far from the rest of the Sun.

Sometimes there is a flare that releases a lot of energy.

To understand the inside of the Sun, one needs a model.

The energy source for the Sun is nuclear fusion.

Nuclear energy is important on Earth too.

The Sun is producing neutrinos that we should be able to detect.

Updated 26 September 2007