Universe Guide

The Sun, our Solar Sytem's Star

The Sun is the closest star to the Earth, it is a mere 149,600,000 km which might seem a large amount but in astronomical terms, its nothing. The next nearest star is Rigil Kentaurus more affectionately known as Alpha Centauri. The Sun is what keeps the planets, asteroids and comets orbiting in . The Sun account for 99.85% of all matter in the solar system. Ref: Slideplayer

In the most simplest terms, the Sun is a giant ball of fire, using 600 million tonnes of hydrogen each second Ref: N.A.S.A. . Its not really a ball of fire, its more a great ball of atomic processes, turning hydrogen into helium. The process of turning the gasses is what gives off the heat for us. It might seem a lot but you have to factor in the fact that there is enough hydrogen in the Sun to last it another five billion years. However life is not expected to be able to survive on Earth for another five billion years. Life will begin to disappear after another one billion years as the Sun starts to expand. By the time the Sun has expanded, it is hoped humanity would have managed to move off the planet, either to Mars or found a way to a Extrasolar Planet. Whilst the Sun might seem to be a destroyer of worlds, without it, all life on Earth will have ceased to exist or not even have existed.

The Radius of the Sun is 695,800 km which is commonly called 1 Solar Radius and when astronomers talk of another Star being 5R, they mean its Radius is about 5 times the radius of the Sun. The Sun is 150 million km. Light moves at 300,000 kilometers/second. Divide these and you get 500 seconds, or 8 minutes and 20 seconds, that is how long light takes to travel from the Sun to the Earth. Ref: Phys

The Sun has a activity cycle of about 11 years when activity on the Sun increases more than usual with Sun Spots and solar flares. When a Solar Flare is ejected, satellite operators such as Inmarsat need to know when the flare will reach the Earth so that they can take action to protect the sensitive equipment on board the satellite. Also astronauts on board the International Space Station are alerted so that they can move into specially protected areas to avoid getting extreme amounts of radiation.

Apart from the fact that Earth, our home planet orbits the Sun and is the only planet known to contain life in the Universe, there is nothing remarkable or outstanding about it. It is no different to any other star in the the milky way.

What colour is the Sun?

The Sun is a dwarf star and as such, its surface temperature is roughly between 5,300 and 6,000k. Actually, the Sun is a white star, the only reason we see it as yellow is because of the atmosphere causes it to appear yellow. It can appear as red in the morning or evening because its lower in the sky and the light potons are scattered. If you see a green Sun, its just false colour imaging, Ref: Ask an Astronomer

Picture of the Sun from the <a href=/fact/internationalspacestation>International Space Station</a>

Difference between Heliosphere and Heliopause

The Sun's influence reaches out to past Pluto, the dwarf planet. The area of influence of a Star or in our case the Sun is known as the Heliosphere and is roughly about 122AU from the Sun. 1 AU is the distance from the Sun to the Earth or 149,597,870.700 kilometers (or 149,597,870,700 meters).

The Heliopause is the edge of the Suns influence and beyond that is Interstellar radiation from other Stars. It was announced by N.A.S.A. on the 12th Setpember 2013 that Voyager 1 had exited the Heliosphere on August 25th 2012 and was now in Interstellar space. Voyager 1 is the furthest satellite/space probe from the Earth. Ref: N.A.S.A.

At the very edge of the Heliosphere is the kuiper belt, a large mass of asteroids that extend out past Neptune. Further out still is the theorized Oort Cloud which is where Comets are said to lie before embarking on their journey towards the Sun.

Heliosphere/Heliopause from NASA

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