Lodestar is a brand new Exotic Trace Rifle added to Destiny 2 with Episode 3: Heresy. Players that managed to pick it up no doubt want to follow up by unlocking the Lodestar Catalyst. The good news is ...
You can purchase the Sunshot from Xûr, Agent of the Nine. Specifically, you can purchase from his Strange offers (random) for 23x Strange Coins.