We have seen that the disks of spiral galaxies contain stars that move in circles in the same direction around the central bulge. the disks contain many bright blue stars that have formed recently, giving them their distinct colors. the disks also often contain bright spiral-shaped arms with darker regions in between. how are these arms related to the stars?

The layers of earth are based on what two sets of characteristics?

In russia which of these challenges affects the transportation of both petroleum products and other goods?

Select the correct answer.look at this nineteenth-century illustration of london. which explanation best relates this illustration to changes in britain in the 1800s? a.factory workers in cities lost their livelihood because of the lack of housingb.industrialization narrowed the inccome gap between landowners and workers.c.the migration of workers from rural to urban areas resulted in overcrowded citiesd.the spread of railways allowed farmers to sell produce far from where it was grown.