A massive body can bend the path of a beam of light as it travels through space; it causes light to travel on a path rather than along a straight line.

Light waves compress as an object is moving toward an observer, causing the light to shift to the end of the electromagnetic spectrum.

Black holes can't be observed directly because they don't produce , so the location is identified by examining the motion of nearby stars.

Even less understood than dark energy is dark , making up 27 percent of matter in the universe and cannot be observed with light.

Holding the Milky Way together is accomplished by the provided by a supermassive black hole near the center of the galactic bulge.

Respond to the following based on your reading.

Explain why the galactic disk appears blue and the galactic bulge appears red.