If you're looking for something intellectually stimulating, a subject I find fascinating is astronomy. The appeal is not just to look at fantastic and otherworldly images but to gain some understanding of the processes involved, as far as I am able.
This is an image of the Orion Nebula, taken from my parents' home (not by me I should add). The nebula is a vast cloud of gas and dust in the process of forming a few thousand new stars. It is visible to the naked eye as a faint fuzzy patch below Orion's belt. Stars are never born alone: only a huge molecular cloud has enough mass to collapse under its own gravity. Our own Sun would have formed in a similar nebula about 4.6 billion years ago, and its many siblings will be scattered about the galaxy by now.
In a few hundred thousand years the radiation from the newly formed stars will eject the remaining gas and dust, stopping star formation. A young open cluster will be left behind, similar to the Pleiades.
The cluster is only weakly held together by gravity, so over time stars escape and are spread out around the galaxy.
If you are intrigued I'd recommend The Science of Discworld
as a very readable starting point for understanding the narrative of stellar and planetary formation, from the big bang to the present day.
Best of luck to you in finding some new interests.