Information about stars indeterminate?

[Helicobacter]

We break down the received light stectrum from a star into the individual wavelength components.

From it we claim to know its composition, heat, distance and speed. Aren't there way more unknowns that knowns?

For example, consider any arbitrary observed star with a certain color distribution. There are many possible configurations of materials which could cause that distribution (material A sucks in these wavelengths, material B sucks in these wavelengths etc.). How can you determine the quantity of each? What's more: if you consider the variables speed and heat, how can we claim to know all of these with just the emitted distribution and intensity?

Also, I am not convinced that we can determine the distribution from a mishmash of different colors. The resulting mishmash could also be the result of many different sets colors being mixed together..

 

[phyzguy]

Have you ever looked at a high-resolution stellar spectrum?

 

[DaveC426913]

Also, I am not convinced that we can determine the distribution from a mishmash of different colors. The resulting mishmash could also be the result of many different sets colors being mixed together..

It is a bit less mish-mashy than you think. Individual lines from specific elements can easily be distinguished from a spectrograph. You would do well to read up on it a bit. Not sure we can lay out the basics here.

 

[Janus]

What's more: if you consider the variables speed and heat, how can we claim to know all of these with just the emitted distribution and intensity?

As pointed out above, each element produces a unique pattern of spectral lines. If we find a pattern shifted from its normal position, it has been Doppler shifted and we can use this to determine the speed of the star relative to us.

Also, the random motions of the atoms producing these lines causes the lines to shift a bit. Since the result is a combination of atoms moving in all number of random directions, the result is to blur or broaden the spectral lines. For a cool object the difference between an atom heading towards us and one heading away due to this random motion is small and the lines are narrower. As the temperature goes up the difference becomes greater and the broadening increases. The shift in the lines overall position gives us the speed and the broadening of the lines gives us a good notion of its temperature.

 

[Helicobacter]

How come we only look at visible light? Do certain elements not suck-in the other frequencies?

 

[Misericorde]

How come we only look at visible light? Do certain elements not suck-in the other frequencies?

They don't only look at the visible spectrum; you need to do your homework.

 

[twofish-quant]

How come we only look at visible light?

We look mostly at visible light because it's easy. If you want to take UV or far-infrared measurements, you have to launch some sort of space craft, and that's expensive (although it's done).

Also you can get nice spectra when you look at microwaves from earth.

 

[Misericorde]

We look mostly at visible light because it's easy. If you want to take UV or far-infrared measurements, you have to launch some sort of space craft, and that's expensive (although it's done).

Also you can get nice spectra when you look at microwaves from earth.

To be clear, those are launched though, for instance to study Sol in the far UV, Radio end of the spectrum, magnetic structure, and so forth. There are two solar observatories being used right now, right? I think one is USA, and one Japanese, but I'm not entirely sure.