Because cosmic distances are so vast, astronomers use light-years as their unit of distance. One light-year is defined as . The nearest star is a little more than light-years away from us. When we see light from a galaxy 2 million light-years away, it has taken to reach us. Light from the Sun takes to reach us.

Because cosmic disaster are so vast, astronomers use light-years as their unit of distance. One light-year is defined as the distance a beam of light travels in one year. The nearest star is a little more than 4.37 light-years away from us. When we see light from a galaxy 2 million light-years away, it has taken 2 million Earth years to reach us. Light from the Sun takes approximately 8.4269 minutes to reach us

Explanation:

i) One light-year is defined as the distance a light beam travels in a time of one Earth year. One light year is equivalent to 6 × 10¹² miles or 9.7 × 10¹² km

ii) The distance to the nearest star =  4.37 light-years

iii) When a star located in a galaxy that is 2.3 million light years away is seen, it has taken 2.3 million light years to reach us

iv) The distance of the Sun to the Earth = 151.58 million kilometers

The speed of light, c = 299792.458 km/s

The time it will take light to reach us from the Sun, 't', is given as follows;

t = 151.58 × 10⁶ km/(299792.458 km/s) ≈ 8.4269 minutes.

hot magma rises and pushes up toward the lithosphere, and as it cools it cycles back down toward the core to be heated again.