This problem requires you to read the following recently published scientific article:
Measuring the ionization fraction in a jet from a massive protostar. Fedriani, R., Caratti o Garatti, A., Purser, S.J.D. et al. Nat Commun 10, 3630 (2019). Link: https://www.nature.com/articles/s41467-019-11595-x.pdf
Answer the following questions related to this article:
(a) Why are massive stars important for the development of the universe?
(b) How can the ionized part of jets be observed?
(c) What kind of region is G35.2N? Describe how it is structured.
(d) What is the ionization fraction χe and how do the authors calculate its value?
(e) How is the mass-loss rate being determined for knots K3 and K4? Why not for K1 and K2?
(f) Why is the ionization fraction so small for G35.2N?
