Between 2 and 3 am, I saw in the sky?

Question

three green lights, forming a triangular shape..They didn't shine at once, just a corner at a time. The last light then zipped across the sky and was gone. This lasted a couple of seconds. I was looking South. What could this be?

Answer 1

Probably a helicopter, judging from the description you give.

In order to point to an Astronomical potential source we would need to know where you are on the earth.

Answer 2

The US military, specifically the Air Force, is flying a triangular shaped craft.  As near as i can tell, it's at least partly held aloft by being a lighter than air craft.  It often flies low to the ground, and distances and speeds can be deceiving.  There are very well documented sightings where people seeing it from multiple places were able to describe the direction - and triangulation was able to get the position and speed information. It was traveling in a line from one military base to another.  I've no idea what it's used for.

Answer 3

Martians