Together we stepped over to the big telechart, a great rectangular plate of smoothly burnished silvery metal which hung at the bridgeroom's end-wall, the one indispensable aid to interstellar navigation. Upon it were accurately reproduced, by means of projected and reflected rays, the positions and progress of all heavenly bodies near the ship. Intently we contemplated it now. At the rectangle's lower edge there gleamed on the smooth metal a score or more of little circles of glowing light, of varying sizes, representing the suns of the edge of the galaxy behind us. Outermost of these glowed the light-disk that was our own sun, and around this Hurus Hol had drawn a shining line or circle lying more than four billion miles from our own sun, on the chart. He had computed that if the approaching dark star came closer than that to our sun its mightly gravitational attracction would inevitably draw the latter out with it into space; so the shining line represented, for us, the danger line.