For the first time ever, scientists believe they have observed a moon orbiting a planet outside our own solar system.

Reported in a press release, scientists at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. say it might just be impossible to verify the existence of what they have called an "exomoon." Even though they only saw it by chance, the researchers believe they will have more opportunities to observe similar spatial bodies like it.

David Bennett, of the University of Notre Dame, and the team published their work in the Astrophysical Journal.

"We won't have a chance to observe the exomoon candidate again," Bennett, the paper's lead author, said in the release. "But we can expect more unexpected finds like this."

Opportunistically observing a meeting of spatial objects outside the solar system, the international team of researchers used a technique called gravitational microlensing. Using telescopes in New Zealand and Tasmania, the scientists would use a star in the foreground as a microscope when it passed between their view and their more-distant target.

Sometimes a star used for microlensing has an accompanying planet, which can then be used to magnify the background even more or add lighting. Sometimes, the telescope will catch a planet on its own and that is where scientists try to find an exomoon.

"One possibility is for the lensing system to be a planet and its moon, which if true, would be a spectacular discovery of a totally new type of system," Wes Traub, NASA's Exoplanet Exploration Program chief scientist, said in the release. "The researchers' models point to the moon solution, but if you simply look at what scenario is more likely in nature, the star solution wins."

The newly discovered exomoon would orbit around a lone planet, which has likely left its own solar system and brought along its moon. Researchers will plan to continue using this lensing technique to try and locate another exomoon.