Final answer:
The great clouds of gas and dust located in the spiral arms of a galaxy are regions where new stars are born. These arms are maintained by gravitational force and are sites of ongoing star formation, as supported by observations and computer simulations.
Step-by-step explanation:
The great clouds of gas and dust in the spiral arms of a galaxy are the birthplaces of new stars and star clusters. In these dense regions, the gravitational pull is strong enough to collapse the material into new stellar objects.
This process is perpetuated by the spiral arms themselves, which are not fleeting features but have enough gravitational force to maintain their structure over billions of years.
Through the study of spiral galaxies like the Milky Way, scientists have observed that bright, well-defined spiral arms typically start forming after galaxies mature, which is around 3.6 billion years. The galactic arms are populated with bright emission nebulae and hot, young stars, indicating ongoing star formation.
It's in these spiral arms that the density of interstellar matter is highest, making them the most conducive places for stars to form.
As galaxies continue to evolve, their spiral arms may fluctuate in brightness due to varying rates of star formation. Advanced computer simulations involving the motions of millions of star particles have supported these observations, illustrating the impact of gravitational interactions on the emergence and stability of spiral arms in galaxies.