ASTR 91 EXAMQUESTIONS WITH COMPLETE SOLUTIONS

all of the following are true. which of these gives evidence that quasars were more common in the early stages of the universe? - ️️they are more common at very great distances approximately how far is the sun from the center of the galaxy? - ️️27,000 light years Based on counting the number of galaxies in a small patch of the sky and multiplying by the number of such patches needed to cover the entire sky, the total number of galaxies in the observable universe is estimated to be approximately - ️️100 billion based on current estimates of the value of Hubble's constant, how old is the universe? - ️️between 12 and 16 billion years old Compared to spiral galaxies, elliptical galaxies are - ️️redder and rounder Compared with our Sun, most stars in the halo are - ️️old, red, and dim and have fewer heavy elements. Compared with stars in the disk, orbits of stars in the halo - ️️are elliptical, with random orientation Dr. Smith believes that the Hubble constant is H0=70 km/s/Mpc. Dr. Jones believes it is H0=50 km/s/Mpc. which statement below automatically follows? - ️️Dr. Smith believes that the universe is younger than Dr. Jones Believes Harlow Shapley concluded that the Sun was not in the center of the Milky Way Galaxy by - ️️mapping the distribution of globular clusters in the galaxy How are interstellar bubbles made? - ️️by the winds of massive stars and supernovae How can we see through the interstellar medium? - ️️by observing in high-energy wavelengths such as X rays and long wavelengths of light such as radio waves How did Edwin Hubble measure the distance to the Andromeda Galaxy? - ️️he applied the period-luminosity relation to cepheid-variables How do observations of distant galaxies help us learn about galaxy evolution? - ️️observations at different distances show galaxies of different ages and therefore different stages of evolution how do we know that halo stars are older, on average, than disk stars? - ️️there are no blue halo stars