How to create 2D glowing effect

Hi, how would I go about creating this sort of 2d glowing effect, you see around planet or the asteroids.

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Tried to google it, but no luck finding any explanation.
Not sure whether this is done only with shader, or generated texture or some gl points/lines with decreasing alpha.

I`m openGl beginner, so pls go easy on me.
Thanks for any help.

It’s most likely a sprite with partial alpha. Possibly using additive blending (as the order doesn’t matter if multiple effects overlap).

But how do I shape the sprites alpha to exact nice looking glows around stuff? And the shape doesnt have to be nice circle, it can be curved etc.