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What if the sun was blue?

  1. Jan 16, 2004 #1
    What if our Sun was a blue giant or was some other color? Would the planet be lit with that color? What would it be like? Our Sun is yellow/orange, but we dont live under that kind of light, our light is more just white, but I don't know why. How would the color of a star be apparent on its planets?
  2. jcsd
  3. Jan 16, 2004 #2


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    names misleading

    The names given to certain types of stars - 'red giant', 'blue supergiant', etc - are certainly colourful, but they are misleading, as you noted wrt the 'yellow/orange' Sun.

    Just three aspects; no doubt others will post many more.

    First of all, your perception of colour depends on many factors, and the mix of wavelengths from the Sun that reach us on Earth is just one such factor.

    Second, all stars but the very coolest ('red dwarfs', 'red giants', 'brown dwarfs') emit light across the whole visible spectrum, from red to violet. This means that for all but these very cool stars, things around you would look pretty much the same colour, if they replaced the Sun (of course, you'd notice huge differences in brightness, you'd die of sunburn quickly under a blue giant sky, etc).

    Third, even if there were a noticable difference, you'd adjust to it quickly, and begin to wonder how colours would change if the Sun were not a blue supergiant!
  4. Jan 17, 2004 #3


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    one major problem with a blue giant, as far as life on one of its planets is concerned, is that the star would last a fairly short time. As a result, it would be a lot less likely that life, or at least intelligent life, would ever form.
  5. Jan 19, 2004 #4
    If you mean... if the current sun was plucked out of the solar system right now and another star was plonked in it's place, what would happen on earth?

    Blue giant
    The surface of the earth would ignite and burn within a minute of the star's radiation hitting earth. All life on the surface would be extinguished within a day. Cept at the whichever pole is in winter season, that'd last a week or so if it was really lucky.

    Red Dwarf
    Over a couple of weeks the earth would freeze. mean surface temp would drop far below -100C. All life forms would slowly die off. The Human race could possibly last for a couple of years if it really got it's act together quick.

    Yep, the sky and light would be much effected by the colour of the star, but it wouldn`t nessacerally be the colour of the star.
  6. Apr 15, 2004 #5
    I predict, our skins would be thick, really thick spongy, and highly reflective. We would live deep in caves, and still get sunburned, but the music would be great, if not piercing, and the radio reception, well, there would be a lot of treble.
  7. Apr 17, 2004 #6

    Math Is Hard

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    Just a quote on Sol's "color" from one of my textbooks...

    "The average temperature of the photosphere (of our Sun) is about 5800 K, corresponding to a thermal radiation spectrum that peaks in the green portion of the visible spectrum with substantial energy coming out in all colors of light. The sun appears whitish when seen from space, but in our sky the Sun appears somewhat more yellow - and even red at sunset - because Earth's atmosphere scatters blue light." - The Cosmic Perspective, 3rd ed, Bennett, et al
  8. Apr 18, 2004 #7


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    the star's temprature will be hotter than now and thus also the planets' tempratures will be hotter.
  9. Jan 23, 2007 #8
    Now I'm not a science or physics teacher or anything.. but I had to do this as an extra credit assignment.. and so far some of the things that have been said.. are false.. like we would not blow up because according to the H-R scale blue is 50,000 C.. which means that Blue is a new star.. red on the other hand means that it is dying or is really old.. and has not a lot of hydrogen left to fuse..

    If our sun was blue.. we would adapt slowly.. everything for us would be tinted blue.. because of the way we see light right now.. we see it as 'white' light.. and if it were to be blue it would change.
    our water would be a gorgeous color blue.. our skin would have a tint of blue in it too..

    No, we would not explode.. One because it takes a star trillions of years to get to a stage where it could even have it possible for it to explode.. it has to be dying..

    now if it was a blue super giant i doubt we would be here because super giants if one was to replace our sun would reach all the way out to jupiter.. but if it was a main sequence star it would just change our light..

    if you think about it.. how many things in the world are caucasion colored.. not much.. so we would be affected..

    this is just my opinion..
  10. Jan 23, 2007 #9


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    Wow, what an old post to dig up. I wont even begin to correct your misconceptions.
  11. Jan 23, 2007 #10


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    I believe ranger, that this is shorthand for talking out of my ass. I'm no expert on the taliban, but I believe that they are all 8 foot cyclops that can only be killed by sustained attacks to the elbows.

    See? It works for anything. :smile:
  12. Jan 27, 2007 #11


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    Well it might actually be an extra-credit assignment.

    How does one manage to assert "it takes a star trillions of years to get to a stage?" when the age of the universe (as we know it) is measured in billions of years - recent estimates put it around 13-14 billion years - and even more recently - "the Universe is about 13.7 billion years old!"

    One can find some useful information here - http://hyperphysics.phy-astr.gsu.edu/hbase/astro/astcon.html#astcon

    http://hyperphysics.phy-astr.gsu.edu/hbase/starlog/staspe.html - Spectral types

    http://hyperphysics.phy-astr.gsu.edu/hbase/starlog/staspe.html#c2 - Blue stars

    http://hyperphysics.phy-astr.gsu.edu/hbase/wien.html - Wien displacement law
  13. Jan 29, 2007 #12
    You guys need to quit pretending to understand physics. Kobriend clearly has the mathematical expertise, as well as the research experience, to falsify widely known and highly empirically supported evidence and physical models in place of his current research topics of interests. Stop pretending to be scientists!

  14. Jan 29, 2007 #13
    Don't forget to mention that our vision would be adapted to the near ultraviolet rather than the visible spectrum.
  15. Jul 24, 2008 #14
    I was just passing through and came across this thread.
    I have a comment to make.
    It seems to me almost everyone has missed the essence of the original question from Nibles. The question does not enquire into the physics of red giant/white dwarfs/exploding stars and an earth gobbled up by giant suns. It is about how the human eye would perceive colours under the light of a blue sun, and what a blue sun would look like from earth.. (all of this with the utopian assumption that the earth and her inhabitants would survive such a drastic change).
    Perhaps this page would interest Nibles, and others here
    <link removed>
    Cheers, all.
    Last edited by a moderator: Jul 25, 2008
  16. Jul 24, 2008 #15
    I doubt Nibles will get around to it. But others here, okay. ;)
    Last edited by a moderator: Jul 25, 2008
  17. Jul 24, 2008 #16


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    Locked for necoposting.
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