M2-9 is an example of a bipolar nebula that resembles two back-to-back rocket nozzles. Is it possible that this shape (somewhat unusual for an explosion) is the result of a time gradient? A rotating ...
How do you tell the difference between a gamma-ray burst and a star just from a picture of a nebula, in which it cannot flash on and off here and there?
The nebulae we see in the night sky are forming new stars. The stars are eating up the nebulae and there is no obvious process in which those nebulae are being created to compensate for that. ...
How functionaly dense are nebulae? Are they so sparse they are only visible from an interstellar or intergalactic perspective or would you be unable to see your hand in one? Do they vary widely in ...