What is Solar Astronomy

The Sun is a main sequence yellow dwarf and is the most frequently studied star in our skies, Solar astronomy is the study of the sun as a star. The sun is 149,600,000,000 metres from earth, and with light traveling at 2.99 m/s, that is eight light minutes. Meaning, as we view the sun on earth the view we see is actually the sun 8 minutes ago, you are effectively looking into the past. The sun provides energy to the earth in the form of radiation, which supports most life forms on earth via photosynthesis. It is the forth-brightest star within 17 light years of the earth.

Since the sun first became a sequence star it has increased in luminosity by 40%, Solar astronomy has various focuses ranging from the life cycle of the sun and the various eruptions and fluctuations of the surface to the timings of the next solar eclipse.

Some solar astronomers take a keen study in the life cycle of the sun. The sun is currently what we call a main sequence star and is the process of gradually heating, those who study the lifecycle of the star work out how fast the sun is heating up and what is likely to be the peak temperature of it before it forms a red giant, (at this point life on earth could easily be literally fried). At current understanding, the sun is around 4.6 billion years old, and will undergo gradual warming for another around 4.5 billion years before forming a red giant, followed by implosion towards a planetary nebula and then a white dwarf, this period from birth to white dwarf totals around 14 billion years.

Another key area of study is the structure of the sun, we currently see the sun as having around 99% of the total mass in our solar system, it is in what we call a plasmatic state (made of plasma) it is pretty much a perfect sphere which spins faster at its equator than at its poles; We know the period of its rotation to be about 25 days at the equator and 35 at the poles. The core of the sun is considered to be one fifth of its total radius, It gives out millions of neutrinos every second and is around 14,500,000 Kelvin and undergoes vast amounts of Thermonuclear reactions every second. The next zone is called the Radiative zone and is around 2,100,000 Kelvin, the convective zone is next followed by the photosphere (the surface) which is around 6000 Kelvin, this is where the visible, infrared and ultraviolet radiation is given up which later reaches earth. Other objects of importance, which are under study, are bright spots, highly magnetic regions (temporarily), coronal loops, turbulent convection and prominence.

The sun also has an atmosphere, which, comprises of 5 major regions: the temperature minimum, the chromosphere, the transition region, the corona and the heliosphere (which actually stretches out past Pluto). Funnily enough the temperature minimum is the area of the sun, which is the coolest, it occurs around 500 km above the surface and is around 4000 Kelvin. We know that this region houses some carbon monoxide and water as there individual absorption spectra have been recorded from this area.

Helioseismology is the study of the propegation of pressure waves in the sun. Solar pressure waves are generated by the turbulence around the surface of the sun, and certain frequencies are amplified by constructive interference. This effectively means, the turbulence “rings” the sun like a bell, in the form of acoustic waves, which are transmitted to the outer photosphere of the sun. This is where the sunlight we receive is emitted. The oscillations are detectable on almost any time series of solar images, but are best observed by measuring the Doppler shift.

Doppler shift is observed in everyday life, driving down the road, an ambulence speeds past, notice how the sound seems to fade and come back into range as it moves away and the pitch of the sound appears to change, this is due to the Doppler effect. As named after Christian Doppler, who said that frequency and wavelength appear to change as the observer moves relative to the source of the sound waves. This distortion can be measured and used to figure out all sorts of characteristics about the wave and what it has traveled through to get to the observer.

By measuring the Doppler shift of the suns photospheric absorption lines, solar astronomers or astro-physicists can work out the magnitudes of various disturbances on the surface of the sun and has helped astro-physicists study solar storms, like cyclones, which form on the surface of the sun.