Comprising some 98% of the solid matter of its own solar system, the Sun is undisputed lord of its demesne. From a distance of nearly 150 million kilometers, we have estimated its diameter to be approaching 1 400 000 kilometers. This stacks up very well indeed against the diameter of its largest sibling, Jupiter, slightly over a tenth of the size.
As for Earth, well .. there’s room for another 333 000 more twin brothers and sisters across the face of Big Daddy!
It’s mass is also greater than that of Jupiter’s, to a magnitude of 1 000. It’s this mass that makes the worlds go round. Yes, yes, Newton was right but it’s the Sun’s colossal mass that gives it the gravitic muscle to keep nine wayward children in line (or circle, as the case may be).
Spectroscopic analysis of the Sun’s numerous effluvia indicate that it is made up primarily of hydrogen, with helium making up the bulk of the remainder – the other elements so very dear to our hearts such as oxygen and nitrogen are, together, a barely-discernible 0.13% of the total.
The heart of the Sun, the core, comprises ten percent of the Sun’s mass and, due to massive compressions above it, is unspeakably dense and hot. It operates at about 16 million Kelvin (one Kelvin being equal to 1.8 degrees Celsius) and has a specific gravity of 160 – that is, it’s 160 times as dense as water; compare that with iron’s measly S.G. of seven.
Being so very, very hot, nothing liquid survives here. It’s not cold enough for molten anything. The heat and denseness also allows for highly efficient nuclear reactions to occur, including fusion of hydrogen into helium – a very energy-giving task.
The energy produced begins it long voyage by being radiated from the inner parts out towards the convection zone of the core, which makes up 15% of it. Here, as you’ve no doubt guessed, the convection of gaseous motions take over duties the radiative zone.
Being cooler here (strictly relatively speaking, that is), more ions can block the photon radiation flowing out of more effectively Kindly Mother Nature kicks in with convection to help, transporting energy from the very hot interior to the cold of space, where no one can hear your teeth chatter.
From the Earth, the deepest part of the Sun that we can really see is the photosphere. This is known as the Sun’s surface as, here, the photons have escaped the core and are free wreak havoc in space. The sphere is about 1500 meters thick and is densely opaque. Using different techniques, measurements show a temperature of 5840 K.
Galileo first discovered sunspots, small dark regions on the Sun’s surface. These spots are cooler than their surrounds by some 1500 K and don’t shed so much light. Galileo used these sunspots to examine solar rotation – yes, even the sun goes round!
The sunspots are regions of enormous magnetic activity. Magnetic fields seem to be responsible for ‘sunspot cycles’. In one 11-year cycle the leading sunspot in a sunspot group has a north magnetic pole while the trailing sunspot in the group will h a south magnetic pole. The polarities are switched, so the total cycle period is 22 years long.
Flares are eruptions even stronger than surge prominences. Carrying a great deal of ionised masses, he solar flare material moves with enough energy to escape the Sun’s gravity.If and when it reaches the Earth, it interferes with radio communication – sometimes causing voltage pulses, surges in power, brownouts or blackouts.
During the numerical peak periods of sunspot activity – solar maxima – more phenomena arise. Prominences are bright clouds of gas forming above the sunspots that follow the magnetic field lines; ‘quiet” ones form in the corona about 40,000 kilometers above the surface and ‘surge” prominences shoot gases up to 300,000 kilometers.
Being made of gas, the rotation is uneven – the equator going full circle in twenty-five days, at thirty degrees above or below taking more than twenty-six days while sixty degrees above or below took up to thirty days