Its second moon claim was featured in a post that garnered more than 16,000 reactions. While it has an Earth-like orbit, that does not make it a “temporary second moon”. Why are people talking about a 'second moon'? A moon orbits around a planet that it is linked to by gravity, like our moon that orbits Earth. In reality, our moon has a diameter of around 3,400 kilometres, while 2025 PN7’s diameter is only 19 metres.