How Big Is the Milky Way?

Answer:

Milky Way; NASA

The immensity of space defies the imagination. The distance involved are so vast that astronomers measure them not in miles or kilometers, but in terms of speed and light, which passes through a vacuum at a rate of 186,282 miles per second. Light from the sun, for example, travels the 93 million miles to Earth in approximately 8 minutes.

But even that distance is just a short hop in astronomical terms. In reckoning the dimensions of space, astronomers use the light-year; this is the distance light travels in one year, or about 6 million million miles. Thus the stars nearest our sun in the Milky Way are 4.3 light-years away. The entire galaxy in turn is about 100,000 light-years in diameter. And far beyond our own Milky Way, in the void of space, uncountable other galaxies are speeding through the immensity of the universe.