Final answer:
Dark matter does not directly affect the lifespan of our Sun but has significant effects on galactic gravitational dynamics, accounting for the majority of the Milky Way's mass and influencing star orbits.
Step-by-step explanation:
The existence of dark matter in relation to the lifespan of our Sun is a complex topic that involves understanding the role of dark matter in the universe. Dark matter does not appear to impact the lifespan of stars like our Sun directly, but it has profound effects on the gravitational dynamics of galaxies. In the vicinity of our solar system, there is no evidence of significant amounts of dark matter affecting planetary orbits or spacecraft trajectories. Further out, in the Milky Way Galaxy, dark matter seems to dominate, suggesting about 90% of the galaxy's mass is in the form of a dark matter halo. This halo allows outer stars to remain in rapid orbits around the galaxy's center. The effects of dark matter are observed on a galactic scale rather than on the scale of individual stars or solar systems.