Which type of galaxy has stars and gas concentrated in spiral arms?

Which type of galaxy has stars and gas concentrated in spiral arms?

• A. Spiral galaxy
• B. Elliptical galaxy
• C. Irregular galaxy
• D. Giant star cluster

Answer: (A)

Stars and gas arranged in spiral arms indicate a spiral galaxy. In these galaxies, a rotating disk contains gas and dust that are organized by spiral density waves, which compress the gas and trigger new star formation along the arms. The bright, young stars in the arms make them stand out, while older stars often populate the central bulge. Elliptical galaxies, by contrast, have a more rounded shape with little gas and dust and lack defined spiral structure. Irregular galaxies don’t show a regular arm pattern, and giant star clusters are not galaxies and don’t feature spiral arms. So the described feature is characteristic of spiral galaxies.

Stars and gas arranged in spiral arms indicate a spiral galaxy. In these galaxies, a rotating disk contains gas and dust that are organized by spiral density waves, which compress the gas and trigger new star formation along the arms. The bright, young stars in the arms make them stand out, while older stars often populate the central bulge. Elliptical galaxies, by contrast, have a more rounded shape with little gas and dust and lack defined spiral structure. Irregular galaxies don’t show a regular arm pattern, and giant star clusters are not galaxies and don’t feature spiral arms. So the described feature is characteristic of spiral galaxies.