Sun - Facts
Our Sun is a normal main-sequence G2 star, one of more than 100 billion stars in our galaxy. Its diameter is 1,392,684 km. [about 865,684miles] its mass is 1.989x 10 to the power 30 kg. It's temperature: 5800 K (surface) and 15,600,000 K (core).
The Sun is by far the largest object in the solar system. It contains more than 99.8% of the total mass of the Solar System. The Sun is, at present, about 70% hydrogen and 28% helium by mass everything else ("metals") amounts to less than 2%. This changes slowly over time as the Sun converts hydrogen to helium in its core. The solar cycle [the magnetic activity cycle] is a periodic change in the amount of irradiation from the sun that is experienced on Earth. It has a period of about 11 years and is one component of solar variation.
The outer layers of the Sun exhibit differential rotation: at the equator the surface rotates once every 25.4 days; near the poles it's as much as 36 days. This odd behaviour is due to the fact that the Sun is not a solid body like the Earth. Similar effects are seen in the gas planets. The differential rotation extends considerably down into the interior of the Sun but the core of the Sun rotates like a solid body.
Conditions at the Sun's core (approximately the inner 25% of its radius) are extreme. The temperature is 15.6 million Kelvin and the pressure is 250 billion atmospheres. At the centre of the core the Sun's density is more than 150 times that of water.
The Sun's power (about 386 billion billion mega Watts) is produced by nuclear fusion reactions. Each second about 700,000,000 tons of hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons (=3.86e33 ergs) of energy in the form of gamma rays. As it travels out toward the surface, the energy is continuously absorbed and re-emitted at lower and lower temperatures so that by the time it reaches the surface, it is primarily visible light. For the last 20% of the way to the surface the energy is carried more by convection than by radiation.
The surface of the Sun, called the photosphere, is at a temperature of about 5800 K. Sunspots are "cool" regions, only 3800 K (they look dark only by comparison with the surrounding regions). Sunspots can be very large, as much as 50,000 km in diameter. Sunspots are caused by complicated and not very well understood interactions with the Sun's magnetic field. Another feature of the photosphere is granulation
Here you see my capture of the sunspots comprising active region 1302, you can clearly see filaments and one of which suddenly fractures releasing a huge M-class solar flare and associated blast wave under some feint magnetic loops.
Here I have captured some post flare loops on the South West limb.
A small region known as the chromosphere lies above the photosphere, this is the layer where solar flares occur sometimes followed by post flare loops in addition to solar prominences/filaments and spicules. Occasionally large unstable prominences/filaments can trigger Hyder flares or even coronal mass ejections [CME]. These CME's are mainly triggered by solar flares associated with active regions.
Here you can see the thin layer of the Chromosphere [about the same thickness at the Earth's diameter] with a huge prominence and numerous spicules briefly poking out.
Occasionally the solar flares can trigger shock waves that travel across the Suns surface like ripples in a pond. These are called Moreton waves and this was my first capture of such an event on the 4th March 2012. Sequence from 10-33 to 11-41UT.
The highly rarefied region above the chromosphere, called the corona, extends millions of kilometers into space but is visible only during a total solar eclipse. Temperatures in the corona are over 1,000,000 K. For further information on solar features check out Calsky.com
Solar Flare Magnitudes:
There are lots of solar flare captures on my website and so here is a chance to view them all in chronological order of magnitude starting with the largest at the top. They ate all my own work except where others there is a credit to right hand side.
M5.7 David Maidment
M1.9 post flare loops