Minecraft crashes when launching

I have a late 2009 iMac, running version 10.10.5, java version 8 update 241.

I try to launch the game from the launcher, and I get the game window briefly before it crashes with a java error. This has happened to me since an update to Minecraft a few years ago. I have not played since, but finally have enough of a bee in my bonnet to ask about a solution. Any help would be much appreciated.