In galaxy clusters, most of the galaxies appear to be elliptical galaxies because O They formed in-situ from low-angular-momentum clouds O They aren't really elliptical, but they look that way because they are very distant O When galaxies collect in clusters, the proximity makes them puffier Galaxies in clusters probably had many merger events in the past

how long do long-exposure photos of two selected areas of the sky reveal that galaxies are very common?

Suppose an alien race on a distant planet tries to send a message to us, with a laser (light). However, we were unaware that there is a stellar-mass black hole almost directly between us and them. How would this complicate our attempts to locate their position in the Galaxy? O Gravitational lensing would make the signal appear to be coming from a different location O The information carried by the laser (light) would be altered O It would not matter The black hole absorbs all of the light

The critical density of a universe is around 5×10-27 kg/m³. Estimate the Hubble constant for this universe.

The Milky Way grew through merging with many smaller galaxies. What are the observational signatures of this process? O The motion of old stars in the bulge and halo of our galaxy are randomly orientated, meaning they were formed from collisions of small, accreted, galaxies all on different paths. O The ordered motion of the bulge / halo stars means that they came from many objects. The random motions of stars in the disk means it was formed from collisions of small, accreted, galaxies. O The motion of young stars in the disk are all in the same direction, meaning they came in as seperate objects.

Distance Based on the graph above, the expansion rate of galaxies near us is than galaxies that are farther away. O faster slower O the same rate Velocity