The first “exomoon” is thought to be as big as Neptune

Ever since Pluto was declassified in 2006 for not being a planet, science buffs have paid close attention to the classification of celestial bodies. Careful taxonomy of our universe leads to better understanding. That’s why astronomers are waffling over the status of the first known “exomoon”:

Last October, Columbia University astronomers Alex Teachey and David Kipping announced that they had spotted evidence of a Neptune-size satellite orbiting Kepler-1625b, a Jupiter-like world that lies about 8,000 light-years from Earth.

Even though 8,000 light-years might sound like a long distance, it’s nothing compared to typical distances in space. Astronomers are excited about the exomoon for good reason.

Firstly, they are pretty sure it is what they think it is. According to the report, David Kipping, a co-author on the study, told reporters that they ruled out other possibilities and that no other hypothesis comes close to explaining the data. Though that doesn’t mean everything is exactly what it seems, it’s a huge step towards learning more about the strange body.

What’s the difference between an exomoon and a moon?

Unfortunately, the answer isn’t too clear yet. Teachey, Kipping’s co-author, explained it in a press conference:

“When we derived the mass ratio, that’s really sort of what I would say, in court, defines the difference between a planet and a moon or a binary planet,” he said. “I would call that a moon, but to some extent I think this is something of semantics — what people want to define as a planet and moon or a binary system.”

Our Earth-moon system has a similar ratio to that of Kepler1625b and its exomoon: 1.2 percent.

Though the fate of the candidate exomoon is not certain, scientists are working hard to figure it out. With more observations and data, we may be able to add the first exomoon to our knowledge of the universe.

Feature image provided via Flickr by Hubble ESA

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