It is a temporary debris field created by an active event.
While the event is active, debris fields can appear in systems on the map for a limited time.
They are recycled using the Recycling mission described in Recycling Mission, but display a badge and a timer in the galaxy.
Their location is not announced: you must find them by navigating the galaxy. Beacons indicate their presence in a system; select that system to see their exact positions and details in the side panel.
Once you know the coordinates, you can still send your recyclers directly from Fleets > Recycling without reopening the galaxy.

