The Sun

Sun

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Sun
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Data

Distance from Earth	Mean 149 597 893 Km (1 astronomical unit) Max 152 103 00 Km Min 147 104 000 Km
Mean Parallax	8sec .794
Distance from centre of Galaxy	25 000 light years
Velocity round centre of Galaxy	220 Km/sec
Period of revolution round the Galaxy	225 000 000 Years (1 cosmic year)
Velocity towards solar apex	19.5 Km/sec
Apparent diametre	Mean 32 min 01 sec Max 32 min 35 sec Min 31 min 31 sec
Equatorial diameter	1 392 000 Km
Density (Water = 1)	1.409
Mass	2 x 1027 tonnes ( about 99% the mass of the entire solar system)
Mass (Earth = 1)	332 946
Volume (Earth = 1)	1 303 600
Surface gravity (Earth = 1)	27.90
Escape velocity	617.5 Km/sec
Luminosity	3.86 x 1026 watts
Mean apparent magnitude	-26.8 6000 000 times as brilliant as the moon
Absolute magnitude	+4.83
Spectrum	G2
Surface temperature	5500°C
Core temperature	15 000 000°C
Rotation period	sidereal mean 25.380 days synodic mean 27.275 days
Time taken for light to reach the Earth	499.012 sec (8.3 min)

Solar Eclipses visible from England (All time calculated from my home location 52° 26’ N 0° 6’ W)
31st May 2003	Start 02:42:20 Max 03:36:27 End 04:32:59	The eclipse is partial from this location. The sun is below the horizon at the start of the eclipse, and rises during the eclipse.
3rd October 2005	Start 07:49:52 Max 09:01:17 End 10:17:31	The eclipse is partial from this location.
29th May 2006	Start 09:47:12 Max 10:34:09 End 11:22:04	The eclipse is partial from this location.

The Sun is our local star. It is of average size, average mass, average composition, average age (4.6 billion years) and average brightness. It is only because the Sun is so close to Earth (about 149597870 km or 108 solar diameters) that it seems an exceptionally bright and unusual star. Light only takes about 8 seconds to reach us, compared to light from our second nearest star (The Sun being the nearest) Alpha proxima C (about 270000 times further away than the Sun) which takes about 4 years to reach us. Each second, the Sun converts about 5 million tons of matter into energy. So far it has used up about half it's availably hydrogen fuel, but it will not be for another 4.6 billion years before the rest is used up and the Sun will turn into a red giant and start the sequence that leads to the Suns eventual death. The Sun produces all it's energy in its core. The high temperature (about 15 million degrees Kelvin) and the intense pressure (250 billion times that on Earth) allow the nuclear reactions to take place. Most of the Sun's mass is in a gaseous blanket around the core, even though the core is about 15 times more dense than gold. Oddly enough this core is in a gaseous state as well because of the intense temperature. (In fact the core is in a state of plasma, which is an ionized gas). The energy in the core heats the Suns surface to 5770°K. The surface of the Sun is called the photosphere. Just above this is the chromosphere and above that is the corona. The corona is further divided into the inner corona and the outer corona. The surface of the Sun is made up of a patchwork of turbulent cells of gas, about the size of Texas that boil up from the Suns interior. Rising from The surface and extending far into space are huge loops of hot gas called prominences. There are also violent eruptions of matter and energy that spew light and charged particles into space, called solar flares. These solar flares often reach Earth and frequently cause auroras, disruption in radio communications and short-circuit in electric power grids.

Sun spots. (Images of Hight sunspot activity 30/03/01)
Dark irregular areas on the Suns photosphere are called Sunspots; they are caused by strong magnetic fields running through the Sun. They run in an average of 11.1-year cycles, going from maximum to minimum cycles. The last maximum was in the year 2000. These spots are about 2000°C cooler than the surrounding area and this makes them seem dark (in fact they are very bright and hot) only because the surrounding area is so bright. They never appear near the poles and are generally confined to latitudes 35° North and South, although they are seldom found on the equator. They generally last only a few days although the larger sunspots and groups of sunspots can last several weeks. The usual unit for estimating the area of sunspots is a millionth of the visible disk of the Sun. This corresponds to an area of around 3 million square kilometers. For a sunspot to be visible to the naked eye they would have to be about 500 millionths. The study of these sunspots crossing from east to west demonstrates the rotation of the Sun, which is faster at the equator than at the poles. The corona. Within one or two solar radii from the surface of the sun, the coronal magnetic field is strong enough to trap the hot, gaseous coronal material in large loops. Farther away from the sun the magnetic field is weaker, and the coronal gas can literally push the magnetic field out into space.