Feeling Heliocentric!

Introduction

T

he Sun is an ordinary star. To us on Earth, it is of crucial importance since no life could exist without it, but it is simply one of billions of stars in the Milky Way Galaxy, itself one of billions of galaxies in the universe. For a star, the Sun is below average size- some astronomers classify it as a “yellow dwarf”. Yet it is massive when compared to the planets. The Sun contains more than 99% of all matter in the Solar System. Its diameter of 1,392,684 kilometres is more than 100 times that of Earth.

According to Stellar Classification, the Sun is a G2V star and is informally designated as a yellow dwarf. G2 indicates its surface temperature of 5778K and V indicates that the Sun, like most stars, is a main-sequence star which generates energy by nuclear fusion of hydrogen nuclei to helium.  In its core, the Sun fuses 620 million metric tonnes of hydrogen each second.

The mean distance of the Sun from the Earth is approximately 149.6 million kilometers (1 AU), though the distance varies as the Earth moves from perihelion in January to aphelion in July.

Internal Layers

At the centre of the Sun is the core, a region of incredible pressure (200 billion times that on the Earth’s surface) and intense heat- about 15 million degrees Celsius. This is the Sun’s nuclear furnace, where the energy that keeps it shining is released. Energy from the fusion reaction flows out from the radiative zone to the connective zone. Here, in a continuous cycle, hot gas bubbles up to the surface before sinking down to be reheated again.

The picture below shows all the layers of the Sun.

An illustration of the structure of the Sun:
1. Core
2. Radiative zone
3. Convective zone
4. Photosphere
5. Chromosphere
6. Corona
7. Sunspot
8. Granules
9. Prominence

Surface of the Sun

The Sun’s outer shell, the Photosphere, is only about 500km thick and, at 5500 degrees, much “cooler” than at the core. It is in a state of constant motion, like water in a boiling kettle. Hundreds of thousands of flaming gas jets, called spicules, leap up to 10,000km into the Sun’s atmosphere, known as the Chromosphere.

Invisible lines of magnetic force that twist around the Sun’s globe are the cause of many extraordinary features. Huge arches of fire, called Prominences, can be held up above the Sun by magnetism. Flares, sudden, massive explosions of energy, burst forth when the magnetic field shifts. Where the magnetic field lines erupt through the photosphere, there are dark, cooler areas known as sunspots. Beyond the chronosphere lies the corona, the Sun’s hot, shimmering outer atmosphere. This is visible from the Earth only during Total solar Eclipses.

Fate of the Sun

About 7 billion years from now, the hydrogen that the Sun uses as furl to create energy will start to run out. Eventually the Sun will balloon into a Red Giant, engulfing Mercury and perhaps Venus too. This is what Earth’s landscape may look like when this happens. Its oceans and atmosphere have gone and its rocky surface is melting in temperatures of 1500 degrees Celsius.

                        

A White Dwarf

The Sun will eventually shed its outer layers into space. All that will remain of the Sun is a White Dwarf, before it eventually cools and wastes away.