Which of the following is not one of the three main strategies used to measure the mass of a galaxy clusters?
A. measuring the speeds of galaxies orbiting the cluster's center
B. studying X-ray emission from hot gas inside the cluster
C. observing how the cluster bends light from galaxies located behind it
D. measuring the temperatures of stars in the halos of the galaxies
Answer:D
Which of the following is not one of the three main strategies used to measure the mass of a galaxy clusters?
A. measuring the speeds of galaxies orbiting the cluster's center B. studying X-ray emission from hot gas inside the cluster C. observing how the cluster bends light from galaxies located behind it D. measuring the temperatures of stars in the halos of the galaxies