What's this???

I was taking a break from studying when I noticed this :

It's the same thing except that one was taken the other way. It's only there when the sun is shining at a particular angle.

Yes, and I know that the pictures are not of the same size, I couldn't be bothered to resize it to the exact same size.

I have no idea what's that!!! And how come it appears!!! There doesn't seem to be anything on my window. BAH. *scrathes head*