In fact, many races have tried to invade Aurora, and many have even succeeded in doing so. But the Gem people have always won every war and remained firmly in control of Aries.
Their alertness and preparedness are one of the reasons why they have been able to maintain a strong grasp of Aurora. These are also why they were able to notice the impending arrival of the mothership and prepare for it even before it set foot in Aurora.
To be fair, the special situation of Aurora is the main reason why they were able to notice the mothership even before it arrived in Aurora. This special situation is the strong magnetic field of the Aurora.
Aueor possesses a very strong and active magnetic field. Its strong magnetic field is why it has a larger-than-normal layer of ionosphere in the upper layers of its atmosphere and why there is a perpetual aurora in the sky.
