Other elements like helium have spectral lines across the blue, red, and
yellow parts of the spectrum.
And so it made it a duller glow of yellow or pale yellow light.
Regardless of the particular characteristics,
the fact that each element has a unique spectral signature means that if you
have a combination of these gases, those elements just add.
If you have a mixture of hydrogen and
helium contained within a gassy experiment.
You'll see the lines corresponding to the sum of both the helium lines and
the hydrogen lines superimposed on each other.
Working this logic backwards, that means if we had an unknown gas and
disbursed it's light into a spectrum, we could diagnose the chemical ingredients.
Spectroscopy actually allows us to go further.
If we have good enough spectroscopy, we could actually look at the profile or
shape of those sharp spectral features and infer the temperature or
the density of that hot gas.
And that's how we learn about distant stars,
the spectral fingerprint is an extraordinary sensitive technique.
In astrophysicists hands, we can detect the presence of trace elements in a star
at constitution of one part in the trillion, relative to hydrogen or
helium, extraordinary trace elements.
All this information can be combined to say what the universe is made of in terms
of constitutes in the periodic table, and their abundance relative to hydrogen and
helium, the most abundant elements.
In astronomy, we tend to see three different types of spectra.