The Sun


Our Sun is the nearest star to Earth
The Sun is the star at the center of the Solar System – almost perfectly spherical and
consists of hot plasma (gas) interwoven with magnetic fields.

The Sun

  • medium-sized and yellow star – measures 870,000 miles across and 109 times the diameter of the Earth in length.

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  • it is made of gases – hydrogen and helium (the lightest gases in the Universe).
  • it weighs 2,000 trillion trillion tonnes – about 300,000 times as much as the Earth’s weight.
  • heating by nuclear reactions to  temperatures of 15 millionºC.
  • visible surface layer of our Sun is called photosphere – sea of boiling gas sends out the light and heat that we see and feel on Earth.

 

  • flames – it’s called spicules dart through a thin layer above the photosphere called the chromosphere.

Chromosphere

  • above the chromosphere – the Sun’s halo `look-like` corona.
  • the heat from the Sun – erupts on the surface called granules or gigantic arcs of hot gases called solar prominence.

Solar Prominence

 

  • why our Sun gets hot? – because of so big and pressure inside the Sun; core is tremendous. (hydrogen atoms to fuse (join together) to make helium atoms, this nuclear fusion reaction is like nuclear bomb to release huge amounts of energy.

Nuclear Fusion Reaction

  • nuclear fusion reactions – five million tonnes of gas into energy every one second, but the energy takes ten million years to reach the surface.
  • the temperature of the Sun’s surface is 6,000ºC – each one centimeter square burns with the brightness of 250,000 candles.

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Cutaway of our Sun with details
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Cutaway of our Sun

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Sunspots


Infrared photographs revealed the sunspots
that appear on the surface of our Sun.

Sunspots

  • dark spots on our Sun’s photosphere (surface) are called sunspots.
  • sunspots are 1500ºc cooler than the rest of the surface.
  • dark centre of the sunspot is the umbra – the coolest part of a sunspot, around the it is the lighter penumbra.

  • sunspots appears in groups that seem to move across the Sun over two weeks, as the Sun rotates.
  • small or individual sunspots may last less than one day.
  • number of sunspots reaches maximum every eleven years – this is called “Solar Cycle or Sunspots Cycle”. (see the video clip: Eleven years Solar Cycles)
  • next sunspots maximum will be around between 2019 and 2023.
  • when sunspots are at their maximum – the Earth’s weather may be warmer and stormier.

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Sun’s eruptions

Solar flares are sudden eruptions on our Sun’s surface

Sun’s eruptions

  • eruptions could flare up in just few minutes, then take more than half hour to die away.
  • Sun’s flares reach temperature of 10 million degrees and have he energy of billions of nuclear explosions.
  • Sun’s flares send out heat and radiation – also streams of charged particles.
  • `Solar Wind` is the stream of charged particles that shoots out from our Sun in all directions at speeds of over one million miles per hour.
  • taking around three days to reach Earth from the Sun, but still blows far throughout our Solar System.
  • every second – Solar Wind carries away over one million tonnes of charged particles from our Sun.
  • Our Earth is shield from the lethal effects of the Solar Wind by its magnetic field.

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Solar prominences

  • solar prominences are giant arcs of hot hydrogen (gas) that sometimes spout out from our Sun.
  • solar prominences reach temperatures of 10,000 degrees.
  • Coronal mass ejections are giant eruptions of charged particles from our Sun – creating gusts in the Solar Wind that set off magnetic storms on Earth.

Solar Wind

  • magnetic storms are massive hails of charged particles that hit earth every few years to set up the atmosphere buzzing with electricity.

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Life cycle of our Sun


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Life cycle of our Sun

  • the time frame of the Solar System’s formation has been determined using radiometric dating – Scientists estimate that the Solar System is over 4 billion years old.

Radiometric dating
(Click here for enlarge)

Our Sun

  • now our Sun around 4.6 billion years old – medium sized star, and halfway through its life.
  • probably live for other 11 billion years times.
  • after 11 billions years, our Solar System is gone.
  • over the next two or three, maybe four billion years, our Sun will brighten and swell until it is twice as bright and 50% bigger.
  • in 5 billion years, our Sun’s hydrogen fuel will have burnt out – inside our Sun’s core will start to shrink.

  • as its core shrinks – the rest of our Sun will swell up and its surface will become cooler and redder.
  • this will be a `Red Giant Star` that you can see compare other stars in our night skies today.
  • Our Earth will burn out long before our Sun is big enough to completely swallow it.

Example: Our Sun will end as a white dwarf.

 

Back to  The Solar System page / next to  The Planets  page.

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