CHICAGO (NewsNation Now) — Astrophysicist Neil deGrasse Tyson says he is skeptical of Demi Lovato’s claim that they had a close encounter last year with an extraterrestrial craft in Southern California’s Joshua Tree National Park.

Lovato said they saw a UFO that resembled a floating blue orb. They said the incident happened last October on her 28th birthday at the national park. They said it was 50 feet away, maybe less, floating above the ground 10 to 15 feet and that it kept its distance from them.

Tyson says that at a time when there are 3 billion smartphones on the planet, the burden of proof should be higher than a person claiming to see a UFO.

“What interests me is not what people say they saw. Because that has certain susceptibilities in the human sensory system,” Tyson said. “Because what you see and what you think you see, what you did see versus how you react, what your emotional state, what your psycho chemical state might have been, all these influence what (we) call … eyewitness testimony.”

However, Tyson says he doesn’t necessarily doubt Lovato’s story entirely, just that he would like to see more evidence.

“I’m not claiming that I can explain everything. I’m just simply asserting that if you want me and many of my scientific colleagues to believe that we are being visited by intelligent aliens from another galaxy or another planet, we need better evidence than what is put forth,” he said.