Hi.
With
key binding you can "unlock" the hidden gradient mesh feature, -above 0.91-, still in development, for a
good start.
Not part of the current svg specs, present only because new cairo renderer -32 bit win built uses an outdated version so there it won't work.
Patches are welcome, so they say.
Other approach would be by using blurring and filter editing.
Here is something similar (the stardust was the goal and not the aurora polaris though).