By NASAs Goddard Space Flight
The “arms” of grand style spirals appear to wind around and into the galaxys nucleus.In contrast to multi-arm and flocculent spirals, which have softer structural components, a grand design spiral galaxy has obvious and well-defined spiral arms. A grand design galaxys spiral arms stretch plainly across the galaxy through many radians and may be seen over a considerable proportion of the galaxys radius.Close evaluation of NGC 3631s grand spiral arms exposes dark dust lanes and bright star-forming regions along the inner part of the spiral arms. Like cars and trucks on the highway, slower-moving matter in the spirals disk creates a traffic jam, focusing star-forming gas and dust along the inner part of their spiral arms.