late 2008 macbook pro - is an os upgrade possible?

i have a late 2008 macbook pro using os el capitan version 10.11.6.

can i upgrade os to sierra or higher? not seeing where this is possible. can only see big sur which seems to serve 2013 or newer macbooks.

i already know it's time for a new machine, just wondering if it's even possible to upgrade to the next os up from el capitan (sierra) or not, and if so, from where might i download and install it?

thanks!