10mtr 1 million light-years 一百万光年 This fat circular disk is our own Galaxy,the Milky Way,with its spiral structure.It travels in space with two satellite galaxies,the irregular little Clouds of Magellan.Not many galaxies are larger than ours;nor are many seen that are smaller than the Clouds. moP.C▣m
一 百 万 光 年
100 thousand light-years 十万光年 We look face-on direcdly at the Milky Way spiral.A hundred billion stars murually bound by gravity encircle the central region,some passing close in,some in wider orbits.Our own sun swings with the rest in dignified passage clockwise about the distant galactic center,once every three hundred million years.External galaxies akin to our own are scat. tered throughout space as far as we can see.They too rotate slowly as they drift. m▣P.C▣m
十万光年
102mter ~10 thousand light-years 一万光年 Clouds of stars and glowing gas,with patches of darkening dust,mark the slow-changing spiral patterns of the Galaxy disk.Our distant sun cannot be seen here,but it is in the center of the image,near the border of one spiral arm. maP.C▣m
一 万 光 年
101 ~1 thousand light-years 一千光年 In this view we are within the disk of the Galaxy,right among a host of stars visible here as individuals.Almost every star of the thousand mapped by the old watchers of the sky. those who first gathered scars into constellations,lies within this square,our own galactic neighborhood.There are many other stars as well,too faint for the eye to see. maP.C▣m
一 千 光 年
71018 aters ≈100 light-years 一百光年 A skyful of distinct stars:One among them,central,but too faint to pick out,is our sun. The star Arcturus,prominent in the northern sky of earth,shines brightly.Arcturus is in- trinsically more luminous than our sun,and here we are nearer to it as well. m▣P,C▣m
一 百 光 年