She's conquered the loftiest theaters on Earth and now Sarah Brightman will take her act to the highest stage on the planet.

The multilingual classical crossover soprano star and actress will head for the International Space Station in September 2015 to become the world's first space diva. Yes, she'll sing in outer space, becoming the first professional musician to do so, and that epoch-making event will be broadcast live around the world.

Like Us on Facebook

The British star won't zoom to the ISS for free. She's agreed to pay a hefty US$52 million for a 10-day stay aboard the ISS.

Sarah will begin training in Russia for her space flight beginning early as this autumn.

Tom Shelley, president of space tourism company Space Adventures, Inc. that is arranging Sarah's outer space concert, said Sarah is " ... absolutely 100% committed. She's putting together her mission plan now."

Sarah has long wanted to travel into outer space and said so publicly in 2012. Her decision to travel to the ISS will make her the first private citizen to visit the orbiting space station since Cirque du Soleil founder Guy Laliberté in September 2009. Laliberté paid US$35 million for this once in a lifetime experience.

Pop star Lady Gaga also plans to be the first singer to perform from "outer space" but she technically won't be in "outer space." The American superstar plans to sing only one song while a passenger onboard a Virgin Galactic space plane.

Lady Gaga will become a space tourist early next year if her plans fall through. The fight as to who'll really be the first diva to sing in space boils down to the definition of "outer space."

The accepted definition of outer space is that part of the atmosphere that lies 100 kilometers or 62 miles above mean sea level. The ISS orbits 400 kilometers above the Earth, which means Sarah will truly be in space.

On the other hand, Lady Gaga will be a passenger on board a sub-orbital plane that will pop into space for less than 10 minutes before returning to Earth.

Sarah will be on board the ISS for 10 days. Lady Gaga's trip will take all of 10 minutes.

Google co-founder Sergey Brin is expected to be the next notable to visit the ISS after Brightman. Brin will likely take to space in 2017.

TagsSarah Brightman, international, space station, sing, Lady Gaga