Ch 28 (for final)

We can estimate the amount of dark matter from the rotation curves of individual galaxies and also by studying galaxy clusters. Which of these is a method for measuring the amount of dark matter within galaxy clusters? Comparing the mass of luminous material in the galaxy cluster to the mass required to keep the galaxies bound and orbiting around the center of mass. Using gravitational lensing, which is the bending of light due to the curvature of spacetime. Measuring the X-ray emission of the gas between the galaxies All of the above

All of the above

How do astronomers know that there aren't significant amounts of dark matter within our solar system?

a lot of dark matter would affect the motions (orbits) of our spacecraft as the move through the solar system, and see no such effect

For every gram of luminous normal matter, such as protons, neutrons, electrons, and atoms in the universe, there are about 4 grams of nonluminous normal matter,mainly intergalactic hydrogen and helium. There are about 27 grams of dark matter, and the energy equivalent (remember Einstein's E = mc^2 ) of about 68 grams of __________.

dark energy

According to the Cosmological Principle, the universe

is isotropic and homogeneous

When astronomers say that the groups of galaxies are distributed isotropically, they mean that

the way galaxies are arranged in space looks the same in all directions