Upgrading 2009 Mac Mini OSX

[KungFuPanda]

I've just been given a Mac Mini from Early 2009. It won't upgrade to OS Sierra as the computer says no.

Is there any way of upgrading to an OSX which is newer than the one that the unit was originally installed with but no as up to date as Sierra?

[KungFuPanda]

Cheers for the tips guys. It's currently running 10.6.8 but if I search for El Capitan on the App Store, it brings up Sierra which I can't download. Will have to buy a disc from Apple.