The Sun - in the prime of its life.
Source: SOHO (ESA & NASA)
Average Distance from the Earth: 149.6 million km (1.0 AU)
Size (Equatorial Diameter):
1 392 000 km (109 x that of Earth)
1.989 x 1030 kg (333 000 x that of Earth)
27.28 days (Synodic Period)
25.38 days (Sidereal Period)
5 500°C (surface)
15 000 000°C (core)
273 m/s2 (27.9 x that of Earth)
The Sun is the star at the centre of our Solar System. It is the largest object in the Solar System, containing 99.86% of its total mass. Due to its great mass, the Sun's gravity dominates the Solar System and holds all of the planets in orbit. The energy it produces through nuclear fusion provides the light and heat for our family of planets.
The Sun is located in an outer spiral arm of the Milky Way Galaxy, approximately 28,000 light-years from the Galaxy's centre. The Sun goes around the Galaxy once every 220 million years. This length of time is known as a Cosmic Year. The Sun's path around the Galaxy is not flat, but goes up and down like a merry-go-round, passing through the plane of the Galaxy every 30 million years.
The Sun is an average yellow, main sequence star of spectral type G2 V. It is middle-aged, at least 4.6 billion years old with an expected lifespan of 10 - 12 billion years.
The Sun is a massive ball of very hot gasses held together by gravity. It is composed mostly of hydrogen (70% by mass) and helium (28%), as well as small amounts of other elements such as oxygen, nitrogen and carbon. It has no solid surface but its atmosphere has several layers.
The Inner Core has only 1.5% of the Sun's volume but half of its mass, and it is here that the nuclear fusion reactions which power the Sun occur. Deep within the Sun hydrogen atoms are fused to form helium, a process which releases incredible amounts of energy.
The energy produced in the inner core must travel out through the Sun's interior. During this journey, which can take millions of years, the energy is transformed into the light and heat that is essential for life on Earth.
The heat and light finally escape from a thin shell called the Photosphere. It is this region of the Sun we can observe and it is sometimes referred to as the surface. The photosphere has a granulated appearance arising from convection currents, like boiling water in a saucepan. There are dark, cooler patches on the photosphere called sunspots, and sometimes large eruptions, called solar flares, send energy and material out into space. Both are associated with the Sun's magnetic field.
Surrounding the photosphere are two more regions. The first is a thin shell called the chromosphere. The other is the outermost part of the Sun's atmosphere called the corona which extends far out into space and is very hot. Both of these regions were first seen during total solar eclipses.