I/ATLAS is just the third recorded interstellar object to enter the solar system. However, the scientific consensus is that it's likely a comet.

In 2017, the mysterious interstellar object 'Oumuamua passed through our Solar System, sparking a heated debate about its true nature. While it was initially considered just another asteroid or comet,

The paper presented several anomalous characteristics of the object, which could indicate that it is not a comet at all but instead a directed craft.