It is impossible for us to imagine a true picture of the size of the universe. It is hard for us even to imagine how big it might be. The earth is part of the solar system, but a very tiny part of it. The solar system consists of the sun, the planets that move around it, the asteroids (小行星), which are tiny, and the meteors (流星). This whole solar system of ours is only a tiny part of another, much bigger system called "a galaxy" (星系). A galaxy is made up of many millions of stars, many of which may be larger than our sun, and they may have solar system of their own. So the stars we see in our galaxy, which we call "the Milky Way", are all suns. They are all so far away that distances are measured in light years instead of in miles. Light travels about 6000000000000 miles in a year. The bright star nearest to the earth is Alpha Centaur (半人马座). Do you know how far away it is 25000000000000 miles! But we are still talking only about our own galaxy. This is believed to be about 100000 light years in width. This means 100000 times 6000000000000 miles! And our galaxy is only a tiny part of a still larger system. There are probably millions of galaxies out beyond the Milky Way. And perhaps all these galaxies put together are still only a part of some larger system! What’s the name of our own galaxy according to the passage