Class 9 gas giant
In planetary classification, a class 9 gas giant planet was the Human designation for a gas giant which was recognized as a Q'tahL class gas giant among Klingons. There were no class 9 gas giants in the Sol system. They were known to exhibit significant EM interference, sometimes known as "siren calls", which were caused by unique waveforms created by the planet's intense magnetic fields. 

The , a Klingon raptor, entered the outer atmosphere of one of these planets to make repairs following an attack by a Xarantine ship in 2151, After the crew became ill and were unable to complete their repairs, the ship began to be pulled in by the planet's gravity, where, it was eventually discovered by the Earth starship  in it's lower atmosphere. ()

ja:クラス9巨大ガス惑星
nl:Klasse 9 gasreus
9
Class 09 gas giant