Baseball field size. Triangular shape. Rotating lights. No noise. Just rose up and eventually disappeared into stars.

I was in middle school which is why I stated 1975 but I am unsure if it was 1976.  
A large dark object with rotating lights slowly lowered itself down toward our house.  It was the size of a baseball field and triangular shaped (per lights).  I can remember as it hovered over top of our tree tops that I realized it would land on our house.  My mother stood outside staring at it while my two sisters and I ran to our basement out of fear.  I just remember thinking how quiet it was. The rotating lights were the only way you could sense it was moving.  It wasn't until our mother also became afraid of it as it was so close.  Once that happened, it slowly raised up.  We then all ran to our large picture window and watched as it slowly just went up toward the stars and actually eventually blended in with them.  I was terrified at the time.  
We all drew a picture that night and I remember our mother told us not to say anything because no one would believe us anyway.  It wasn'! t until recently I mentioned something to one of my siblings and they just blurted out about that same incident.  
We live near a PP & L power substation and on a farm.  I often thought our front yard looked almost like a cleared runway.
Witness indicates that the date of the incident is approximate.  PD