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Red Giants in Space, the Biggest Stars!

Updated on October 22, 2011

A RED GIANT is a huge, exploding red star in the latter phases of it's cosmic evolution. In terms of mass, it has about the mass of one-half to ten of our suns (otherwise it'd be a supernova!), but the radius of this star is almost unimaginably immense, hundreds of times that of our sun.

The star has exhausted it's supply of hydrogen to fuse. It no longer has any. It is now fusing the hydrogen in the shell of the star, outside it's core. The initial phase of the star, after it's formed from a molecular cloud, uses the hydrogen at it's core to fuel it by nuclear fusion. So does our sun. This is what powers our sun, and hence the life on earth.

So, the star has exhausted it's supply of hydrogen. The nuclear reactions at it's core stop. The core starts contracting, due to gravity. This heats a shell around the core, where hydrogen remains, initiating the fusion of hydrogen to the helium in it's shell. Higher temperatures lead to increasing reaction rates, a domino effect that makes this star 10,000 times brighter than our sun.

Our sun will become a red giant in about five billion years. I don't know if we humans need to worry very much about this. A lot can happen in five billion years. Cosmologists (who used to be called astronomers) think the Sun will become large enough to engulf the orbits of all the planets up to Earth, and it's radius will expand exponentially.

When it goes to the red giant state, what it gains in volume it loses in mass. it loses a lot of it's mass--the mass is consumed in this last glorious fire. It may lose enough of it's mass to be unable to retain the outer planets as satellites. They may fly off into space, untethered to their former courses by the now-insufficient gravity of the sun. Mercury and most probably Venus will be swallowed by the Sun's expansion.

What will happen to Earth? It might also be engulfed. Or, it might widen it's orbit, due to the decreasing mass of the sun, enough not to be swallowed up. It might retain enough of it's angular velocity to keep in orbit without becoming engulfed.

In any case, the flare from the sun will have burnt all the life on the planet to cinders, pre-supposing that life still exists on the planet five billion years from now. It is too vast a time for the mind of man to comprehend, but does give one some perspective on the ultimate necessity of space exploration. 4,999,999,999 years from now the matter will seem pretty much more urgent.


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    • profile image


      8 years ago

      only 4,999,999,999 years? ;)

      i can't begin to imagine what Earth will be like then. groovy hub! i rated it UP.

    • Paradise7 profile imageAUTHOR


      8 years ago from Upstate New York

      Thank you, myownworld. I'm awed, truly, by the vastness of the scale. It's almost incomprehensible to the mind of man.

      Yes Duchess, a wee 4,999,999,999,999 years! LOL!

      You're very welcome, Catherine R. I really enjoy writing these.

    • Catherine R profile image

      Catherine R 

      8 years ago from Melbourne, Australia

      Thank you for this little series. Our universe is amazing - and I am really ignorant of these matters. Less so now though! So thanks.

    • profile image

      Duchess OBlunt 

      8 years ago

      4,999,999,999 years from now? Is that all? LOL

      Great Hub Paradise!

    • myownworld profile image


      8 years ago from uk

      one is left with such a feeling of awe when reading and learning about the universe...esp. relatively unknown subjects like these. just loved this...!

    • Paradise7 profile imageAUTHOR


      8 years ago from Upstate New York

      Thank you, creativeone, CMHypno, and Veronica, for your comments. I enjoyed looking into these topics, and it was a re-education. Science has come a long way since I last studied these things.

    • Veronica Allen profile image

      Veronica Allen 

      8 years ago from Georgia

      This is so awesome to me. It's amazing how even nature see's the need to "recyle" itself by a its continuous change. Nothing goes to waste - not even energy. At the risk of going of tract, I think this is a grand lesson for us. Much like the elements in nature that are constantly changing and evolving, we have the capacity to reuse, recycle and change or convert old things into new, instead of throwing things out and allowing them to pile up in landfills.

    • CMHypno profile image


      8 years ago from Other Side of the Sun

      Interesting info on Red Giants - we live in a fascinating universe.

    • creativeone59 profile image

      benny Faye Douglass 

      8 years ago from Gold Canyon, Arizona

      Thank you for a very educational hub on the Red Giant, thank you for sharing. creativeone59


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