If the mass estimates are correct, the HR 8799 system is the first multiple-planet extrasolar system to be directly imaged.

Our solar system has its own interplanetary dust cloud; extrasolar systems too.

The concept has also now expanded to include worlds not only in the Solar System, but in hundreds of other extrasolar systems.

As of 2008, 221 extrasolar systems have been found.

It is also the first extrasolar system around a normal star with measured coplanarity.

He called this "a final proof that the first extrasolar planetary system has been unambiguously identified."

The possibility that this could be the first known extrasolar planetary system, not just a solitary planet detection, has generated excitement.

Every colony world had the same defense because no extrasolar system had been studied in enough detail for asteroid impacts to be predictable.

Of the recent discoveries of extrasolar planetary systems, few have enough known planets to test whether similar rules apply to other planetary systems.

Most known extrasolar planetary systems appear to have very different compositions to the Solar System, though there is probably sample bias arising from the detection methods.