International astronomers confirmed this week that they might have spotted the first "exomoon" ever, according to NASA.
An exomoon is a moon orbiting a planet that lies outside the solar system.
The astronomers don't want to say what it is for sure until they've completed further analysis. It could also be a huge planet orbiting a small star, according to NASA.
Research was published in the Astrophysical Journal.
"We won't have a chance to observe the exomoon candidate again," lead author David Bennett of the University of Notre Dame said in a statement released by NASA. "But we can expect more unexpected finds like this."
The possible exomoon was discovered during a study led by Microlensing Observations in Astrophysics (MOA,) which is a joint venture led by Japan, New Zealand, and the U.S.
The Probing Lensing Anomalies NETwork (PLANET) program also contributed its telescopes located in New Zealand and Australia.
Astronomers were able to find the possible exomoon by using a technique called gravitational microlensing. This process works when one star passes another as seen from Earth.
The closer of the two stars can be used like a magnifying glass to brighten and focus the light of the more distant one for either days or weeks, depending on what is required.
The study shows that astronomers found that the ratio of the larger body compared to its smaller one is 2,000 to 1. The nature of the foreground lensing object is "not clear," according to NASA.
This means that the pair could either be a small star circled by a planet with 18 times the mass of Earth, or the planet is larger than Jupiter and has a moon weighing less than Earth, according to the study.
They currently can't tell which scenario is correct.
"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," said Wes Traub, chief scientist for NASA's Exoplanet Exploration Program office at NASA's Jet Propulsion Laboratory, who was not involved in the study, according to NASA.
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