I just started a game of ME3, and I got a side quest to find the Shrike Abyssal. However, the quest is not showing up in the Galaxy Map. Where should I be going?
According to a forum thread on the official forums you need to finish the Palaven moon mission to get the Shrike Abyssal to show up on the galaxy map.
I did pay attention to this while playing myself and the system also only appeared for me after the Palaven mission.