The sun is our ‘giver of life’ but it will take it very quickly if given cause, our friend and enemy, the governor of seasons and master weather maker-controller.
The sun is our ‘giver of life’ but it will take it very quickly if given cause, our friend and enemy, the governor of seasons and master weather maker-controller. Master irrigator, the sun can and does move vast amounts of moisture around our planet with impunity aided by wind currents etc.
In days gone by I have been astounded by the amount of water it could move or indeed remove from one of our major cities water supply dams – tens of millimetres in one day spread over the entire dams surface is one ‘heck’ of a lot of water.
If one was to take note of that sort of evaporation on a smaller water supply such as ‘farm’ dams for instance, the water loss can be catastrophic and in places over seas such as north eastern Africa, to mention only one spot (Ethiopia for instance) life is lost every day to thirst and dehydration. However, that same evaporation on a really grand scale is, in another location on earth the devastating flood that seems to generate and strike from nowhere.
Imagine if you would how much water is sucked skyward from a position such as ‘Lake Eyre’ in South Australia without mentioning of course the vast oceans that surround our planet. So couple ‘Sol’ with wind and other weather factors and you have life’s governor’s who are for ever at work somewhere on our planet. These forces can be managed with huge benefit if treated with respect but forget your place or be careless and tragedy can follow quickly.
On the other hand we draw our vitamin ‘D’ needs from the sun, we sun bath in it and we consume food reaped from plants and animals which are also reliant beneficiaries of our stars benevolence, so give it some thought – without it we are ‘goners’!
Our solar systems star is listed as a G2V (spectral type) yellow dwarf, a population 1 heavy element (such as gold, uranium) star our suns birth was probably brought about by a nearby supernova and its affect on a nearby cloud of gas and dust.
The sun shines in our heavens with blinding brilliance, so please do not look at it unless you have the special filters to do so (www.astroshop.com.au). The penalty for carelessness is severe and can result in skin disease and blindness.
The sun has an apparent magnitude of -26.8 and an effective temperature at the photosphere of 5778 kelvin. Positioned around 8 parsecs or 25-26 thousand light years from the galactic centre within the inner rim of the Orion Arm of the Milky Way Galaxy. The sun makes one revolution of the Milky Way about every 220-250 million years at a velocity of around 250klm/sec and in concert with other stars in its vicinity it travels at about 20klm/sec on a path that leads it out to a point somewhere between ‘Hercules’ and ‘Lyra’ near one of our brightest stars known as ‘Vega’ or ‘Alpha Lyra’. The point or position mentioned above is known as the Solar Apex and its coordinates are as follows – RA 18h, DEC + 30 degrees.
The constellation of Lyra (just to get right off topic) is incidentally home to the beautiful ‘Ring Nebula’. This object is an easy one to find in your telescope, appearing as a soft blue-ish ring (hence its name) NGC6720 or M57 is set at a distance of around 2,300-2,500 light years.
I have heard the sun referred to as a ‘fire ball’ and I suppose in layman’s terms that will suffice but in reality it is so much more than that. People have worshipped it for thousands of years and indeed evidence of such activity is recorded in nearly every country in the world where there was an early population. Two races that stand out most in my mind are the American Indians and all their various groups coupled with the Ancients from the Middle Eastern area, Egyptians, Assyrians, etc.
Our sun is with no doubt the largest body in our solar system taking up 99% of the total mass and consists mainly of Hydrogen and Helium. It has and equitorial diameter of about 1.4 million kilometres which equates to 109 earths lined up across its face and I think something like 1,300,000 earths can be squeezed inside.
The nuclear fusion area at the suns centre can convert 700 million tonnes of Hydrogen into 690 million tonnes of Helium every second, the remaining 10 million tonnes is energy generated by that fusion activity which finds its way to the surface in around 10 million years having been re-absorbed and re-emitted several times in that process. Given that the suns consists of material of a gaseous nature it has different rotation speeds from the equator to the poles they range from 25.05 days a the equator to 30 odd days at the poles. However, viewed from earth the sun has an apparent rotation period of 28 days as well as being nearly a perfect sphere with only 10 kilometres difference between its polar and equatorial diameters.
Most of the suns thermal energy is generated within the first 20-25% if the suns radius with nearly all fusion stopped by 30% of radius. The rest of our suns heat (energy) seems to come from the energy transferred out to outside layers from the core. Once on the surface it transmits into space as sunlight or kinetic energy particles.
Due to the fact that we can’t observe the inner solar sphere we use a technique similar to seismology where shockwaves reveal the inner layers of earth. Helio-seismology however, uses pressure (infrasound) waves from ‘Sun Quakes’ travelling through the suns interior to map its inner layers. So from the inside of our star to the outside visual surface we have:
- The Core
- Radiative Zone
- Convective Zone
I use a ‘white light solar filter’ from Thousand Oaks Optical which prevents 99.999% of sunlight from entering your telescope. This is a really safe option and allows one to view the solar globe and sun spots. We are presently in cycle 24 and scientists are somewhat concerned that there isn’t as yet any sign of cycle 25 which should be detectable forming at the Poles. A Sun cycle is usually in the vicinity of 11 years although there is occasionally a lapse between. We must realize that although a heap is known about our Solar Systems energy source, our study of ‘it’ is still in its infancy.
Sunspots are primarily an electro magnetic disturbance or an interplay between magnetic-radiation and convection and are about 1,000 degrees cooler than the surrounding material which shows them to be darker. From an amateur, such as myself, point of view it is a thrill to discover and track them from day to day as they traverse the face of the Sun.
I’m just a simple fellow with an interest and enough knowledge to get me into trouble but boy there’s some good work being done to understand our star fully, it’s exciting and it’s happening now!
First observation by satellite was I believe undertaken by NASA when it launched “Pioneer 5’ in 1959. This was followed by 6, 7, 8 & 9 the later being launched in 1968 or thereabouts. It (Pioneer 9) transmitted until May, 1983.
In the 1970’s Sky Lab with its ‘Apollo Telescope Mount’ and two Helios Space Craft gave their contribution. Helios 1-2 were USA-GERMAN and studied the Solar winds. Sky Lab was launched by NASA in 1973 and is credited with the discovery of ‘Coronal Holes’ as well as observing ‘Coronal Mass Ejections’.
The Solar Maximum mission used to study Solar Flares, X-Rays, Gamma Rays and UV Radiation was launched on 1980 by NASA and was followed in 1991 by a Japanese craft named ‘Yohkoh’ or ‘Sun Beam’. This craft (satellite) studied Solar Flares at X-Ray wavelengths for a complete solar cycle and eventually entered the atmosphere and burnt-up in 2005.
Our most significant mission (solar) yet was and is the ‘Solar and Heliospheric Observatory’ launched by NASA and the ESA in December 1995 and still operates to date, in fact it enjoys an extension till 2012. The Solar Dynamics Observatory (SOHO) was launched in 2010 as a follow-up to the above and is situated at the Lagrangian point between the Earth and the Sun (a point where gravity pulls the same from both directions). This satellite provides a constant solar watch and has been able to see many small bodies (such as small comets) either grazed or burnt up due to close encounters.
Ulysses Probe took up the challenge in 1990 and its mission was to study the suns polar regions. Its route to deployment was a sling-shot via Jupiter where (luck would have it) it managed a marvellous view of Shoemaker-Levy 9 colliding with our largest planet in 1994.
One other mission of note was ‘Stereo’ or The Solar Terrestrial Relations Observatory which was launched October, 2006. this consisted of two (2) identical craft, one in front of the Earth and one behind. These craft we designed to gain on and fall behind Earth respectively. This manoeuvre would allow a stereo view of phenomena like Coronal Mass Ejection and also stereo imaging of the Sun at any time.
Ok! folks, as before I’m not going to delve to deeply into the physics of this. My intention is simply to draw your attention to our Solar life giver and hope that my ramblings have sewn a seed or two. The more you read on this topic the more compelling it becomes. I know that on days when its not in our heavens there’s a definite sense of ‘loss’, just like it has an influence on our moods as well as the weather and almost everything else that happens and has happened on our planet since time began.
So I’m going to leave you with that thought and hope you will look up on occasions – believe me the rewards are many!
As usual my thanks must go to my reference sources – Nortons Star Atlas, found at good book shops. Atlas of the Southern Night Sky by Steve Massey and Steve Quirk, obtainable from www.astroshop.com.au and good book shops. Google has quite and extensive coverage of this and other closely related topics. Importantly ‘Australia Sky and Telescope’ magazine – obtainable from most newsagencies.
So long folks and I’ll see you out there one dark night when the seeing is good.