Bem, minhas suspeitas foram confirmadas no episódio 1x12, o final da primeira temporada, Tudo está quebrado :
An ancient ship, the Kaziri, crashed on Earth and is hidden at the bottom of the town mines. To quote Nolan and Doctor Yewll, it has a weapon that can "kill every human being on the planet - or every Votan, depending on how you use it".
According to the Earth Republic representative, the Indogene have been searching for it for almost 3000 years. Given that they were not active while in the 5000 year hypersleep journey to Earth, this would seem to indicate the ship was discovered by Indogene around 8000 years ago. The stellar collision in the Votanis system 5000 years ago would simply have been an excuse to make the journey.
Aside, I do not call it an Indogene ship as the technology behind it that we've seen so far doesn't look Votan in origin. And the search would seem to indicate that the weapon aboard is stronger than the Indogene (the most technologically advanced of the Votan) are capable of.