De or het planeetvorming?

The correct Dutch article is:

de planeetvorming

Rule Words ending in -ing: almost always de. See the rule

How to use planeetvorming

the planeetvormingde planeetvorming
this planeetvormingdeze planeetvorming
that planeetvormingdie planeetvorming
our planeetvormingonze planeetvorming
your planeetvormingjouw planeetvorming
every planeetvormingelke planeetvorming
which planeetvorming?welke planeetvorming?
a big planeetvorming / the big planeetvormingeen grote planeetvorming, de grote planeetvorming