Question

what can we discuss better by using the theory of electromagnetism?
a group of stars that are located between polaris and the northern hemisphere horizon
the graph astronomers use to show the relationship between a stars absolute magnitude and temperature
runaway stars and the paths that they travel
the different types of light, both visible and invisible

Explanation:

Electromagnetism theory deals with the relationship between electricity and magnetism and is fundamental to understanding electromagnetic radiation, which includes all types of light (visible and invisible). Stars' location, star - magnitude vs temperature graph, and runaway stars are more related to astronomy concepts like celestial mechanics rather than electromagnetism.

Answer:

the different types of light, both visible and invisible