Simple sun/star question...

[Crodley]

Hi folks,

 

Here's an elementary question my wife and I were wondering.

 

From something I read recently, the sky looks blue and the sun appears yellow, because the atmosphere filters the blue from the white light from the sun and bounces it around.

 

Now if that is fact, why do most stars at night appear white instead of yellow? Why does the atmosphere not filter out the blue from that smaller spectrum?

 

Waiting for the easy answer I assume is out there.

 

Crodley

[Bettina]

Hi folks' date='

 

Here's an elementary question my wife and I were wondering.

 

From something I read recently, the sky looks blue and the sun appears yellow, because the atmosphere filters the blue from the white light from the sun and bounces it around.

 

Now if that is fact, why do most stars at night appear white instead of yellow? Why does the atmosphere not filter out the blue from that smaller spectrum?

 

Waiting for the easy answer I assume is out there.

 

Crodley[/quote']

 

The stars are really different colors. They appear white to us because of the nature of the human eye. We can't detect color in objects that are too dim so our eye will perceive them as white.

 

If you look at stars through a telescope, they will have color because of the increased brightness that the lens gives us..

 

Bee

[[Tycho?]]

Its kinda wierd that people call the sun yellow.

 

Go out at noon one day, and glance upwards. What do you see? You dont see a yellow light, you see a white light. In fact I think the color of the sun is the definition of "white" light. It only appears yellow when it is setting, and the light is scattered a lot by going through so much atmosphere.

[The Peon]

Color denotes temperature. White stars are very hot and are usually young. Red stars are the coolest, and can generally be much older.

[blike]

To add on to the above posts (particularly Betinna's), the sun is classified as a "yellow star". However, it is true that the atmosphere does have some effect on how yellow this appears.

 

Stars appear white is because of the type of cells being used in your eye. Objects that aren't very bright are usually handled by "rod" cells. They are ultra-sensitive, but they don't detect color--just light. So at night, you're using your rod cells to pick up the starlight. Thus they appear colorless. As Betinna noted, if you look through a telescope you'll notice that many stars take on a different color: red, blue, white, yellow, etc.

 

Here is my source and a good article for more explanation: http://www.badastronomy.com/bad/misc/starcolors.html

[Crodley]

Thanks for the replies! Very interesting stuff. My wife and I are enlightened.

 

Crodley

[ecoli]

 

The Ultraviolet Sun

 

X-Ray Sun

[RyanJ]

Apparently we are missing images for the last two so here are links to some:

 

Ultraviolet:

 

http://alexis.m2osw.com/images/sun_ultraviolet.jpg

 

X-rays:

 

http://crab0.phys.nthu.edu.tw/~hchang/sky/ch01/f01-01-25-sunXray.JPG

 

Cheers,

 

Ryan Jones