What colour is the sun??

[pcchen]

Acoording to NASA, the average albedo of the moon is 0.12 (of course it depends on the phase of the moon as perceived on earth).

 

[Spaceman-Spiff]

Is google such a difficult URL to type?
http://www.earthsky.com/shows/listenerquestions.php?date=20030929

CC

Use a link like this next time .

 

[Fruitfrenzy]

Acoording to NASA, the average albedo of the moon is 0.12 (of course it depends on the phase of the moon as perceived on earth).

According to my Starry Night astronomy software the sun is magnitude -26.9 and the full moon is -12.6.

A difference in magnitude of 1 is usually considered to be a factor of 2 difference in brightness so that would indicate a difference factor of around 20,000. Given that the light a full moon is still quite dark and our perception of brightness is non-lilnear I think that is reasonable.

 

[Captain Chickenpants]

Use a link like this next time .

What you want me to do all the work for them!

 

[pcchen]

According to my Starry Night astronomy software the sun is magnitude -26.9 and the full moon is -12.6.

A difference in magnitude of 1 is usually considered to be a factor of 2 difference in brightness so that would indicate a difference factor of around 20,000. Given that the light a full moon is still quite dark and our perception of brightness is non-lilnear I think that is reasonable.

Ugh, the moon does not reflect 0.12 of all sun's light. Far from it. First, the moon is much smaller than the sun.
Well, there's no second point.

[EDIT] I think I should clarify somethings... Actually on full moon about 7% of the lights are reflected, not 12%. Furthermore, the moon is not a perfect mirror, so it diffuses the incoming lights. Therefore, the distance between the earth and the moon should be considered. That's why the moon looks much darker than the sun.

 

[Blade]

All of the pictures I've seen of the sun close up show it to be black/red/orange/yellow.

A simple explanation but it's what I've witnessed.

 

[nutball]

All of the pictures I've seen of the sun close up show it to be black/red/orange/yellow.

That's an artificial colour table more than likely.

 

[drpepper]

All of the pictures I've seen of the sun close up show it to be black/red/orange/yellow.

A simple explanation but it's what I've witnessed.

That's probably due to the EM spectrum that the camera is filtering for.

The sun is white as the EM radiation it emits ranges from low IR to high X-ray. This totally engulfs the visible spectrum that WE can observe.

 

[Fred]

One second of googling rather than making a long post.

http://www.madsci.org/posts/archives/1999-12/945169710.As.r.html

So there you have it. Its whiteish with peaks in the yellow. I would have gone by the H-R diagram classification and called it yellow, but whatever.

 

[OpenGL guy]

The sun is white as the EM radiation it emits ranges from low IR to high X-ray. This totally engulfs the visible spectrum that WE can observe.

The fact that it emits across the whole visible spectrum doesn't make it white as there could be a red or blue bias. The sun is considered yellowish white based on its surface temperature of about 5700 K (quite cool compared to larger, hotter stars), not on how we perceive its color visually. Sirius, a star about 2.4 times the mass of the Sun, is considered a white star.

(I checked Wikipedia to confirm my facts and to provide more precise data.)

 

[Neeyik]

(I checked Wikipedia to confirm my facts and to provide more precise data.)

Umm, I don't think you checked Wikipedia close enough :

http://en.wikipedia.org/wiki/Stellar_classification

It should be noted that while these descriptions of stellar colors are traditional in astronomy, they really describe the light after it has been scattered by the atmosphere. The Sun is not in fact a yellow star, but has essentially the color temperature of a black body of 5780 K; this is a white with no trace of yellow which is sometimes used as a definition for standard white.

This might be more appropriate I think:
http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html
http://www.erin.utoronto.ca/~astro/ast110/lectures/colours.html

 

[OpenGL guy]

Umm, I don't think you checked Wikipedia close enough :

http://en.wikipedia.org/wiki/Stellar_classification

*shrug* I read that page and compared the Sun's surface temp with the list. The list says "yellowish white". There's nothing in the table to indicate that this is not the color.

I can't help it if Wikipedia wants to contradict themselves on the same page.

 

[soylent]

According to my Starry Night astronomy software the sun is magnitude -26.9 and the full moon is -12.6.

A difference in magnitude of 1 is usually considered to be a factor of 2 difference in brightness so that would indicate a difference factor of around 20,000. Given that the light a full moon is still quite dark and our perception of brightness is non-lilnear I think that is reasonable.

One magnitude is a factor ~2.5(The fifth root of 100). The apparent brightness of the sun for a viewer on earth is about 400 000 times brighter than the full moon.

 

[IgnorancePersonified]

Don't know what gas ball you guys are orbiting but I am going to go off that Cher movie and say it looks "hot"

 

[soylent]

*shrug* I read that page and compared the Sun's surface temp with the list. The list says "yellowish white". There's nothing in the table to indicate that this is not the color.

I can't help it if Wikipedia wants to contradict themselves on the same page.

Because colours are very much perceptual. You wouldn't call your standard 3000 K light bulb "orange-red" would you? Colours change drastically when you put them against different surroundings(!).

edit: here's a similar list for metals which are pretty good blackbodies: http://www.processassociates.com/Process/heat/metcolor.htm

If you want to remove all perceptual issues you could just look at the frequency where the blackbody radition's energy output is highest. But that doesn't tell you a thing about the visual appearance of the lightsource. http://en.wikipedia.org/wiki/Wien's_law , that puts the sun in the yellow/orange-ish part of the spectrum. But our eyes' sensitivity to green light is about 20 times higher than it is for red light so I don't think it would look particularilly yellowish.( a colour temperature of 4000-5000 K on a monitor or flourescent tube is percieved as slightly bluish white).