Rotate object to head to magnetic north in ARCore

Question

I want to rotate an object so it heads to magnetic north, for example I want to create a compass needle, how can I do that? I can rotate objects in local space like below, but how to align to real world North:

Node solarControls = new Node();
solarControls.setParent(sun);
solarControls.setRenderable(solarControlsRenderable);
solarControls.setLocalPosition(new Vector3(0.0f, 0.25f, 0.0f));
Quaternion orientation1 = Quaternion.axisAngle(new Vector3(0.0f, 1.0f, 0.0f), 90);
solarControls.setLocalRotation(orientation1);