WASHINGTON An unnamed bidder paid $28 million at auction Saturday for a seat alongside Jeff Bezos on board the first crewed spaceflight of the billionaire's company Blue Origin next month.

The Amazon founder revealed this week that both he and his brother Mark would take a place on board the company's New Shepard launch vehicle on July 20, to fly to the edge of space and back.

They will be joined by the winner of Saturday's charity auction, whose identity will be disclosed in coming weeks, and by a fourth, as yet unnamed space tourist, according to Blue Origin's director of astronaut and orbital sales Ariane Cornell.

Saturday's successful bidder beat out some 20 rivals in an auction launched on May 19 and wrapped up with a 10-minute, livecast frenzy.