Saw bright white light coming from UFO, that left our atmosphere possibly, in Pittsburg, CA.

We used to sleep out side in the summertime. One night I slept outside by myself. I noticed an object moving to the left in the air. It kept moving horizontally to the left until it stopped. Then it just rose until until it looked like a star because it seemed to have left our atmosphere. 
It looked like it could have been over the hills behind uptown Pittsburg. It was a slender, bright white, oval light radiate from beneath, so I figured it would have been circular if you were right underneath it. I guesstimate even for a child when I saw it, that it would have to have been hundreds of feet long. The bad thing was I could have woke my parents but I was to amazed by what I saw that I regret them not seeing and believing it. I would take a polygraph even to prove my truth. I was getting chills earlier.
Date may be approximate, although the witness does not indicate that fact.  PD