system
Given the following post, respond as if you're commenting on Reddit:
human
[Halo] If the Jackal home-world's parent planet is known to us now, and is with in the forty light-year expanse of human colonies, does that mean that the UNSC would've of sent a colony ship to the planet, if so do we ever hear about such a ship?
gpt
The Jackal home system contains no planets which are near the Earth in size, only gas giants. The Jackal homeworld is a moon of one of these gas giants, which would make it much harder to detect by usual exoplanet detection methods than a lone planet of that size on its own. 

The UNSC may not have known it was there, or may have been more interested in colonizing planets, and so not sent an expedition. Prior to the Human-Covenant war, slipspace travel was pretty slow and slispace-capable ships were very expensive. It would be unlikely for a ship to be sent on a multiple-week journey to a system that isn't thought to contain anything useful.

European nations didn't explore every landmass in the Atlantic before setting up colonies in the Americas, there were islands that weren't explored until centuries later. Similarly, although this system isn't too far from Earth, that doesn't mean it would be explored immediately.