I came across this weird one transistor LED-blinker circuit with a backwards connected BJT.
It works, and the LED strobes nicely at a few Hz.

But how exactly does the circuit work?
I have also been playing around with the values a bit. It seems to run with a capacitor as small as 10nF, and up to a frequency of about 50kHz.
What I have found out so far is that the transistor seems to act as a Zener diode at about 8.5V but with decreasing voltage for increasing current, forming a negative resistance region.
This could be part of what makes it oscillate, but why does the transistor behave in this way?