Class 6 gas giant

From Memory Alpha, the free Star Trek reference.

In planetary classification, a class 6 gas giant is a type of gas giant planet.

In 2375, the crew of the USS Voyager ordered their new multispatial probe deep into the atmosphere of a class-6 gas giant, to prevent it from being stolen by the Malon. The probe became lodged in a layer of liquid hydrogen and methane, and was later retrieved by the Delta Flyer. (VOY: "Extreme Risk")