The five-year-old gelding, trained by Kevin Ryan, showed that his 40-1 second to Winter Power in the Nunthorpe Stakes at York last month was no fluke as he took the Group One showpiece over six furlongs.
Art Power burst out of the stalls and soon set up a decent lead, with Supremacy leading the pack and Emaraaty Ana close to the pace.
Emaraaty Ana (11-1) picked off Art Power over a furlong out and set sail for home.
Starman, who was under pressure some way out, stayed on strongly - but Emaraaty Ana held on by a short head. Chil Chil was three-quarters of a length back in third, with Happy Romance fourth.
Ryan said: "He deserves it, we've started riding him patiently and the horse has come alive for doing that.
"I've had huge faith in the horse and I'm delighted he's done it. He's as good a horse as I've trained - his work in a morning is brilliant.
"All my team at home have done a great job, we're delighted."
The winner was introduced at 16-1 for the Breeders' Cup Turf Sprint, and Ryan signalled Del Mar as the target - for a race he won last year with Glass Slippers.
He added: "I think that's where you have to go now."
The prestigious victory brought up a treble for Andrea Atzeni after his earlier wins on Triple Time and Artistic Rifles.
The rider said: "He's a horse that everyone kept faith in.
"I can't tell you what it means to me to win another Group One, it's been a couple of years since I won one.
"Things can go a bit quiet, but it's all about the horses and I had a good one underneath me."
A dejected Ed Walker said of Starman: "There's no excuses, it's disappointing."