View previous topic | View next topic

why are there no green stars?

Page 1 of 1

b3spoke
131155.  Wed Jan 03, 2007 6:22 pm Reply with quote

there are red, orange, yellow and blue stars, but no green ones.

anyone care to hazard a guess as to why?

 
AlmondFacialBar
131159.  Wed Jan 03, 2007 6:33 pm Reply with quote

there are no green stars because the colour of stars is determined by the temperature they're burning at. depending on the heat, matter can appear black, brown, read, yellow, white or bu-ish white. green just isn't in there.

:-)

AlmondFacialBar

 
legspin
131161.  Wed Jan 03, 2007 6:48 pm Reply with quote

Seemingly our own sun is close to being such an entity. The problem arises in that our eyes just aren't set up to seeing it. Stars such as our own put out a goodly part of their energy in the middle of the visible section, ie. yellow-green, but they also put out the other colours. Our eyes are just not sensitive enough to differenciate between the various intensities of colour so we just see it as white. The stars we see as red or blue are also just an average (sort of anyway) colour, that is they are outputing a particular part of the spectrum and what we are seeing is amalgam of all the colours that star is. At the edges of the visible spectrum, as some are, they would also be putting out infra-red or ultra-violet. We of course can't see them so we see more of the red and blue in their make-up.


Last edited by legspin on Wed Jan 03, 2007 6:50 pm; edited 1 time in total

 
mckeonj
131162.  Wed Jan 03, 2007 6:49 pm Reply with quote

It is possible for any white star to appear green under certain viewing conditions. This phenomenon is known as 'the green flash'. Here is a picture of the sun (which is a star), showing green at sunset.



and here a Wikupedia article on the phenomenon.
http://en.wikipedia.org/wiki/Green_flash

 
dazed
131275.  Thu Jan 04, 2007 10:49 am Reply with quote

If enough of one of the green flame chemicals (e.g. Ba, Tl, Zn etc)was introduced to a star would it turn green or would this distroy the star? Is this somwthing which could happen (either by natural or artificial means)?

 
Severnbore
131276.  Thu Jan 04, 2007 11:05 am Reply with quote

I think you are right - and would amplify further to say we naturally regard our sun's output as white by default - and as you say that has a lot of green with less red and blue. Hotter stars have their peak output at a bluer wavelength so we see blue (white with more blue than we are used to) and cooler stars peak in the red - more red than we are used to.

There is no way for a star to have more green than we are used to - in normal atmospheric conditions - see green flash post !

legspin wrote:
Seemingly our own sun is close to being such an entity. The problem arises in that our eyes just aren't set up to seeing it. Stars such as our own put out a goodly part of their energy in the middle of the visible section, ie. yellow-green, but they also put out the other colours. Our eyes are just not sensitive enough to differenciate between the various intensities of colour so we just see it as white. The stars we see as red or blue are also just an average (sort of anyway) colour, that is they are outputing a particular part of the spectrum and what we are seeing is amalgam of all the colours that star is. At the edges of the visible spectrum, as some are, they would also be putting out infra-red or ultra-violet. We of course can't see them so we see more of the red and blue in their make-up.

 
grizzly
131282.  Thu Jan 04, 2007 11:52 am Reply with quote

dazed wrote:
If enough of one of the green flame chemicals (e.g. Ba, Tl, Zn etc)was introduced to a star would it turn green or would this distroy the star? Is this somwthing which could happen (either by natural or artificial means)?


Simple answer, no.

The light produced by stars is not made by combustion (materials burn when they react with oxygen forming an oxide and usually producing heat, this is what happens to the elements that you described). The light from stars is produced by the fusion of hydrogen atoms into helium. Towards the end of a star's life it will begin to fuse heavier elements in its core, a stage when these stars often turn into red giants. When they explode in a supernova these heavier elements are blasted into space. All of the heavier elements on the Earth (including those that make up your own body) will have been formed in a star and blasted out into space in a supernova.

Most stars contain very little oxygen so the elements you describe would not combust in that way.

 
Gray
131433.  Fri Jan 05, 2007 5:18 am Reply with quote

Here's a pretty full answer, along the lines already mentioned:

http://www.astronomycafe.net/qadir/q72.html

 
did you know....
131576.  Fri Jan 05, 2007 12:55 pm Reply with quote

how do we know there aren't, there might be we just havent found them yet

 
djgordy
131613.  Fri Jan 05, 2007 3:17 pm Reply with quote

It can be your homework to find some green stars then.

 
mckeonj
131671.  Fri Jan 05, 2007 6:45 pm Reply with quote

I can tell you where the green stars might be found, if that is any help:
in the spaces between the stars we can see
There you are.

 
b3spoke
132697.  Tue Jan 09, 2007 11:30 am Reply with quote

thanks for the replies.

 
Ford Prefect
136637.  Fri Jan 19, 2007 8:02 pm Reply with quote

There is a relationship between the wavelength of a stars light and the colour at which photosynthesis occurs, which is why plants are green on Earth.

There is no reason why plants on other planets couldn't be other colours, they could still do photosynthesis at another colour determined by the stars colour and the atmosphere.

I know this is not quite an answer to your question, but it is I think somehow related.

 

Page 1 of 1

All times are GMT - 5 Hours


Display posts from previous:   

Search Search Forums

Powered by phpBB © 2001, 2002 phpBB Group