Conclusion

In examining spectra, astronomers have developed powerful techniques to determine a lot of detail about stars, galaxies and composition of inter stellar space, in spite of their great distances.

We can:

• determine chemical composition and temperature,
• distinguish stellar classes from sub-dwarfs all the way to super-giants,
• and thus estimate mass, age and luminosity.

In other EBooks we can learn more about how these spectra help us to determine distance and radial velocity. With that information we can study multiple star systems, find planets around other stars and even observe the expansion of the Universe.

Credit: Menlo Systems

The great advantage of spectral astronomy is that it does not matter how far away the celestial object is. Astronomers even study the spectra of objects in the outer reaches of the known Universe at distances up to 13 billion light years.

There is continued R&D in the technique of spectroscopy, which paves the way for ever more exciting discoveries. See e.g. here

Further reading

• In the EBook “Stellar Distance” we further discuss the link between luminosity and distance and we also explain how the line spectrum is used to very accurately measure radial velocity in space;

• In the EBook “Stellar Evolution” we discuss the life cycle of stars and will come back to the HR-diagram.