Bluish/greenish light flashing on a white object traveling faster than any figher jet with no sound.

Sitting outside in our backyard, my husband and I were star gazing, when an unusually fast white object with a blue/green, maybe turquoise flashing light, traveling south to north, pulsating the bluish light.  At first glance, I thought it was a fighter jet, but it went faster than anything I have seen in the sky, including a fighter jet, and there was no sound.  We jumped up to follow it and it continued out of view northward.  We lost sight of it within 10-20 seconds.  About five minutes later, it came back from north to south; however, lower than it had been and we only saw it for about three seconds.