Science Buddies: "Ask an Expert"

This year for my science project I am doing the Rainbow Fire project; I am determining what stars are made of and how hot they burn based on what sorts of light they give off. In the beginning I thought that I would observe the color and temperature of a color-flamed candle and then correlate it to the star based on the color (like the transitive property in geometry; if A=B, and B=C, then A=C. In other words, If this flame is blue, and it is made of Iron, and burns at a thousand degrees, then a blue star must be made of iron and burn at a thousand degrees.) But now I am not sure- my science club teacher ordered me a spectroscope (I know what it is and how to use it), along with a few other things I have no idea about. It feels like it should be a more complicated procedure- Is there any chance someone could explain what I need to do? (preferably a dumbed-down version.)

This is an intriguing project and a great idea you have. Astrophysicists do observe the spectra of stars using special telescopes and they may find bright lines in the spectrum that correspond to the emission of certain atoms like hydrogen, helium, calcium, titanium and iron: http://cas.sdss.org/dr3/en/proj/advance ... /lines.asp

However, the composition of a star is not the main factor in determining its color. The surface temperature and how long the star has been burning are the main things that affect the color of its emitted light: https://www.quora.com/What-determines-t ... r-of-stars

So, if you saw a yellow star, for example, I don't think you could conclude that it contains a lot of sodium, a metal that produces a yellow color in a flame.

Were you planning on hooking up your spectrometer to a telescope to get actual spectra of stars? That would be really cool if you could do that, but I suspect it is rather difficult. If you live near a university that has an astronomy department, you could ask them about stellar spectra. They may be able to show you some examples of ones that they have produced.

I don't know if this helps, but please do repost and let us know what you are planning to do. When you get the spectrometer you should be able to get spectra from copper, strontium, sodium and other metals when you put them in a flame. If you have a digital camera or smart phone why don't you try to take pictures through the spectrometer. That would be a great way to display your results on a science fair poster.

Good luck!

Sybee

To add onto what Sybee correctly said

The surface temperature and how long the star has been burning are the main things that affect the color of its emitted light

The temperature is determined by the mass of the star (how much stuff is in it). So we see that very heavy stars burn very hot and emit very energetic light. The higher the energy, the shorter the wavelength and so the more blue it will look. Consequently, how long a star has been burning is a factor because it's mass will change over time as it uses its fuel and so emit light primarily in longer and longer wavelengths shifting from the blue side of the spectrum towards the red. The link below includes a good graphic on spectral classifications of stars with the stars temperature being shown in the kelvin scale.

http://www.enchantedlearning.com/subjec ... ypes.shtml