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If I asked you to draw a picture of the sun, which crayon would you pick? Most people would
reach right for yellow or if it’s sunset, maybe you pick orange… unless you grew up
in Japan, where children usually choose red.
But it’s safe to say that no one would pick this, the real color of the sun.
It’s true that down here on Earth, the blue and violet wavelengths in sunlight are scattered
away by the atmosphere, making the sun appear slightly yellow, or even orangey red… but
from above Earth’s atmosphere, the sun is essentially white.
Sorry Superman.
When we see pictures of the sun from outer space in movies, TV shows and even pictures
from astronomers, it's often tinted orange to seem more familiar to us.
But really, this screen can’t even display the true color of the sun. The images being
beamed onto your retinas right now are mixtures made of red, green, and blue light, the intensities
of which are varied to trick your cone cells into the sensation of any visible wavelength,
or mix of wavelengths. This color… is really these colors.
When metal’s been put into a fire, it starts to glow, first red hot, then white, and at
its hottest, even blue, as it releases thermal energy as electromagnetic radiation.
That's pretty metal.
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This emitted blackbody radiation is a mix of certain wavelengths whose lengths depend
on the temperature.
When things get really, really hot, they can emit into the ultraviolet. You and I are emitting
radiation right now, but it’s down in the infrared… because we’re so coooool.
Our sun is about 5800 Kelvin, and the radiation it gives off is centered in the visible range…
which is exactly why it’s the visible range, because that’s what we evolved to see…
but I digress! Across the universe, stars of all different
temperatures give off different mixtures of light. Cooler stars appear red, while the
hottest stars are blue.
If you know just where to look, you can see colored stars for yourself, in the blue of
Sirius, the brightest star in the night sky.
By examining the light given off by that star, and countless others across more than 200,000
galaxies, astronomers have determined the average color of the universe:
They call it cosmic latte.
And what about us, the Milky Way in that cosmic latte? In 2012 astronomers determined the
color of our galaxy too, and captured it in a haiku:
Look at new spring snow See the River of Heaven
An hour after dawn
Stay curious.