A 16-year-old schoolgirl had finished playing tennis with her mother in the British town of Leamington Spa on April 11, when the teenager and others saw something highly unusual in the sky -- a large black ring, moving very slowly above trees. After several minutes, the mysterious object disappeared, but not before the teen captured the ring on her iPhone.
Watch this video of the black ring above the U.K.'s Leamington Spa.
A variety of theories, speculation and explanations poured forth after the black ring images were released. They ranged from a faked video, weather phenomenon, swarm of mating insects to birds.
"The ring definitely is not a swarm of birds or insects, nor a weather phenomenon. I believe the girl's video is real and not faked," said Ben Hansen, a former FBI special agent and host of the Syfy Channel's "Fact or Faked: Paranormal Files."
"It's just a very cool effect made usually by a device which goes by many names: smoke ring generator, smoke cannon or vortex cannon," Hansen told The Huffington Post in an email. "The construction usually involves a pipe on a stand that is filled with a combustible liquid, like gasoline, kerosene or other oil and a pressurized gas, such as propane, which explodes expanded gases through the pipe nozzle."
Hansen explained how this same effect has been used for years at art and music festivals, such as the annual Burning Man event in Nevada.
Watch this black smoke ring being formed at the 2008 Nevada Burning Man festival.
"It takes a calm day with no wind for the ring to stay hovering in the air for a lengthy time," Hansen wrote. "But when it does, it's quite impressive."
HuffPost also reached out to Marc Dantonio, chief photo and video analyst for the Mutual UFO Network, to get his take on the U.K. aerial black ring. He agrees with Hansen.
"The black ring is not an ET event -- 100 percent sure," Dantonio told HuffPost in an email. "That is a phenomenon caused by a pipe that shoots a charge of propane or gasoline straight up. Because the fireball was symmetric around the upward facing pipe, you get a symmetric spherical fireball at first. As the fireball extinguishes itself, the ring forms from the turbulent upward rising air and the smoke continues to be drawn up in the rising heat column.
"As the center dissipates from being accelerated through the middle, the outside remains relatively intact."
They could both be right. According to the Leamington Spa Courier, a spokesperson for the nearby medieval Warwick Castle suggested that the smoke ring was the result of some pyrotechnics in use at the historic castle's attractions.
"As part of our 1,100th anniversary celebrations this year, we've been testing a number of fire effects to enhance our daily Trebuchet Fireball Spectacular show -- the world's largest firing catapult," the spokesperson said. "We've seen a number of different effects, including the vortex images that have been reported. ... It's certainly a spooky spectacle."