What is a galaxy rotation curve?

A graph showing the brightness of stars at different distances from the galactic center A graph showing how fast stars orbit at different distances from the galactic center A diagram of the spiral arms of a galaxy A map of the dark matter halo around a galaxy

What did Vera Rubin and Kent Ford discover when they measured rotation curves of spiral galaxies in the 1970s?

Stars at the outer edges orbit much faster than stars near the center Stars at the outer edges orbit much more slowly, confirming predictions Stars at the outer edges of galaxies orbit just as fast as stars closer to the center Stars near the center of a galaxy orbit more slowly than expected

What did physicists expect galaxy rotation curves to look like, based on the visible mass of the galaxy?

Orbital speed should increase with distance, because outer stars have more room to accelerate Orbital speed should decrease with distance from the center, like planets orbiting the Sun Orbital speed should stay exactly the same at all distances Stars near the center should orbit slowly because the black hole pulls them back

What does a flat rotation curve imply about the mass distribution of a galaxy?

Most of the galaxy's mass is concentrated at its very center The galaxy has no mass beyond the visible stars There must be a large amount of mass spread throughout an extended halo around the galaxy, far beyond the visible stars The galaxy's mass is evenly spread only within the visible disk

Who first noticed a missing mass problem in galaxy clusters in 1933, decades before Rubin?

Edwin Hubble, who discovered galaxies were moving away from each other Fritz Zwicky, who measured the speeds of galaxies in the Coma Cluster and found they moved too fast for the visible mass to hold them together Albert Einstein, who predicted missing mass in his theory of relativity Henrietta Leavitt, who studied Cepheid variable stars

How large is the dark matter halo compared to the visible part of a spiral galaxy?

The halo is about the same size as the visible disk The halo is smaller than the disk but much denser The dark matter halo is much larger and more massive than the visible galaxy, extending far beyond the disk of stars The halo only exists near the center of the galaxy around the black hole

Why is Vera Rubin's contribution to astronomy considered so important?

She discovered the first exoplanet orbiting another star She proved that the universe is expanding by measuring galaxy speeds Her careful measurements provided the most compelling and widely accepted observational evidence that dark matter exists She developed the theory of general relativity and predicted dark matter mathematically

Why did Vera Rubin never receive the Nobel Prize for her discovery?

Her results were never fully accepted by the scientific community She died in 2016 and the Nobel Prize is not awarded posthumously The Nobel Committee awarded the prize to Fritz Zwicky instead She declined the prize because she did not want the attention

Which of the following is analogous to the problem Vera Rubin discovered?

A bicycle wheel that spins faster the harder you push it A planet that orbits the Sun at the same speed regardless of how close it is A merry-go-round where the riders at the outer edge spin just as fast as those near the center, even though no visible motor is pushing them A clock whose hands all move at the same speed

What is the term for the invisible mass distributed in a roughly spherical region surrounding a galaxy?

Galactic corona Baryonic shell Dark matter halo Invisible disk

Why are rotation curves described as the most compelling evidence for dark matter?

Because rotation curves can be measured with complete accuracy using radio telescopes Because Albert Einstein predicted flat rotation curves using general relativity Because the same flat pattern is seen in virtually every spiral galaxy studied, ruling out measurement error and requiring a systematic invisible mass component Because computer simulations prove dark matter must exist