 |
Diameter/km
Mass/kg
mean density kg/m^3
Surface gravity
Escape velocity
mean temperature |
1390000
1.989e30
1408
274.0m/s^2
617.6km/s
5800k
|
The Sun is a medium sized star yet its energy and violence almost defy imagination. The Sun is a dense mass of helium and hydrogen which is in a permanent state of nuclear activity making it self luminous unlike planets which shine when they reflect light from a star. Each second 4 million tons of hydrogen are destroyed which start somewhere near the core where temperatures reach 5 million degrees centigrade. At the top right of the image above a huge prominence of gas can be seen arching some 350,000km into space, an arch has formed as a result of following part of the Sun's magnetic field. Prominences are denser but cooler than the gas of the surrounding cornea, where temperatures reach 2 million degrees. Why the cornea should be some 250 times hotter than the Sun's surface is one of the outstanding puzzles of solar physics. The Sun like all stars is created by the simplest known element coming together, hydrogen. These gases built up to form a star nursery where the gases came together. It became a star when the weight of the gases became so huge that its gravity became much greater causing atoms of hydrogen to fuse into helium. The Sun converts some 600 million tons of hydrogen into helium every second, a process that has been going on since the Sun's birth 4.6 billion years ago. The Sun is so massive being 100 times the diameter of the Earth that it has sufficient stocks of hydrogen to power it for a further few billion years.
Unfortunately nothing lasts forever, eventually the Sun will run out of it's hydrogen fuel causing the core to shrink. This will build up temperatures and pressures sufficiently to initiate the fusion of helium atoms into carbon, a reaction which will increase the Sun's energy output. When this happens the Sun will expand into a red giant, dozens of times larger and hundreds of times brighter than our middle aged Sun. As the Sun swells, the earth's oceans will boil dry and all life on Earth will become extinct except for cockroaches probably which can survive in extreme conditions.
