Need asap : the aging process of a star is referred to as:       the main sequence the evolution white dwarf the nebula

Astronomers call a star's ageing a stellar evolution.

Explanation:

Astronomers call a star's ageing a stellar evolution.

Stellar evolution is the mechanism through which a star changes constantly with time.Based on star's mass, its lifespan can vary from a several million years for most massive to least massive trillions of years, which is significantly longer than that of the universe itself.

d₁ = displacement of tern from arctic to antarctic = 11000 miles

d₂ = displacement of tern from antarctic to arctic =   - 11000 miles

d = total displacement for the journey

total displacement for the journey is given as

d = d₁ + d₂

d = 11000 + (-11000)

d = 0 miles

t₁ = time of travel from arctic to antarctic = 3 months = 3 x 30 days = 90 days

t₂ = time of travel from antarctic to arctic = 3 months = 3 x 30 days = 90 days

t = total time of travel

total time of travel is given as

t = t₁ + t₂

t = 90 + 90

t = 180 days

average velocity is given as

average velocity = total displacement/ total time

v = d/t

v = 0/180

v = 0 miles/day