Are they extraterrestrial ... or ultraterrestrial?

Because there's still a lot of mystery behind the UFO and alien phenomenon, there's a debate as to whether Earth's enigmatic visitors are actually. extraterrestrial. Some ufologists believe these beings could be from a parallel universe or from a higher dimension that humankind is incapable of seeing. If that is the case, these beings would instead be considered ultraterrestrial. Also, an all-encompassing theory is presented that attempts to explain the reason why Earth is apparently playing host to extraterrestrial beings.
Interdimensional hypothesis - Wikipedia
The Difference Between Extraterrestrials And Ultraterrestrials - KnowledgeNuts
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