void PlanetTree_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs <object> e)
        {
            var body = e.NewValue as CelestialObject;

            if (body == null)
            {
                return;
            }
            var mapIcon     = MapCanvas.Children.OfType <IMapIcon>().Single(icon => icon.Body == body);
            var childCoords = new Point(mapIcon.X, mapIcon.Y);

            ZoomControl.ZoomAndCenter(0.25, ZoomControl.ChildToParent(childCoords));
        }