A question on the abundance of the elements

[mech-eng]

How can scientists determine,calculate or understand that in the universe hydrogen is the most abundunt element as there are thousands of galaxy with their own planets. There might even an undiscovered element that could be most abundunt.

Have a nice day.

 

[Baluncore]

By examination of the absorption and emission spectra of the stuff out there, it is possible to estimate the abundance. http://en.wikipedia.org/wiki/Fraunhofer_lines
The second most abundant element is helium. The first evidence of helium came in 1868 from an unexplained emission line in sunlight.
http://en.wikipedia.org/wiki/Helium#Scientific_discoveries

There are no obvious stable places left in the table of isotopes, any undiscovered elements on the periphery of the stable zone can be expected to have extremely short lifetimes, so they really cannot be abundant.

 

[Astronuc]

How can scientists determine,calculate or understand that in the universe hydrogen is the most abundunt element as there are thousands of galaxy with their own planets. There might even an undiscovered element that could be most abundunt.

Have a nice day.

One would have to sample galaxies/stars/planets to look at emission lines, and make some estimates of mass, in order to determine the relative abundance of elements in the cosmos.

Locally, we would have to take rock samples, and then make estimates on various geologic structures in order to estimate the relative abundance of elements.