# Was the sun once a blue star?

**URL:** <https://boards.straightdope.com/t/was-the-sun-once-a-blue-star/160295>\
**Category:** Factual Questions\
**Created:** [March 10, 2003, 1:42pm UTC](https://boards.straightdope.com/t/was-the-sun-once-a-blue-star/160295 "2003-03-10T13:42:41Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\
**Post date:** [March 10, 2003, 1:42pm UTC](https://boards.straightdope.com/t/was-the-sun-once-a-blue-star/160295/1 "2003-03-10T13:42:41Z")

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Just wondering… I believe the sun is following what is known as the “Main Sequence”. If this is correct, would the sun have been a blue star in its youth? - Jinx

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**Author:** ![Ice\_Wolf](https://avatars.discourse-cdn.com/v4/letter/i/dfb087/32.png) [@Ice\_Wolf](https://boards.straightdope.com/u/Ice_Wolf)\
**Post date:** [March 10, 2003, 1:46pm UTC](https://boards.straightdope.com/t/was-the-sun-once-a-blue-star/160295/2 "2003-03-10T13:46:17Z")

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According to [this site](http://astrosun.tn.cornell.edu/courses/astro201/evol_sun.htm) the sun glowed red before Main Sequence, not blue.

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**Author:** ![Urban\_Ranger](https://avatars.discourse-cdn.com/v4/letter/u/e9c0ed/32.png) [@Urban\_Ranger](https://boards.straightdope.com/u/Urban_Ranger)\
**Post date:** [March 10, 2003, 2:04pm UTC](https://boards.straightdope.com/t/was-the-sun-once-a-blue-star/160295/3 "2003-03-10T14:04:07Z")

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Huh?

Yes, the sun is a yellow main sequence star. That means it will continue to be a yellow star until it becomes a red giant. It won’t change into another colour, and was never another. The colour of a star, determined by its surface temperature, is a function of its mass.

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**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\
**Post date:** [March 10, 2003, 2:10pm UTC](https://boards.straightdope.com/t/was-the-sun-once-a-blue-star/160295/4 "2003-03-10T14:10:19Z")

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Stars do not follow the Main Sequence. They spend most of their lifetime at a single point along it. So, for its entire MS existence, the sun, or any other star, remains the same color (more or less). You are right, though, that at different points along the main sequence, a star’s color would be different.

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**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\
**Post date:** [March 10, 2003, 2:17pm UTC](https://boards.straightdope.com/t/was-the-sun-once-a-blue-star/160295/5 "2003-03-10T14:17:35Z")

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Anyone got a link to a good, color, H-R diagram?

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**Author:** ![Ice\_Wolf](https://avatars.discourse-cdn.com/v4/letter/i/dfb087/32.png) [@Ice\_Wolf](https://boards.straightdope.com/u/Ice_Wolf)\
**Post date:** [March 10, 2003, 2:21pm UTC](https://boards.straightdope.com/t/was-the-sun-once-a-blue-star/160295/6 "2003-03-10T14:21:59Z")

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Would [this help?](http://www.astro.ubc.ca/~scharein/a311/Sim/hr/HRdiagram.html)