Describe how gravitational lensing works. What can it tell us about a quasar? What can it tell us about the galaxy that is doing the lensing? How is lensing valuable to the study of dark matter?
What will be an ideal response?
Gravitational lensing occurs when a nearby object (normally a galaxy) bends the light of a distant object (often a quasar), causing two or more images of the distant object to be seen. It is useful in studying the distant quasar, because the images have different travel times, allowing transient events to be observed more than once. The lensing galaxy can have its mass calculated based on the amount by which it bends light. This lets us study dark matter by comparing the lensing galaxy's luminous mass with its gravitational mass.
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If you had something the size of a sugar cube that was made of neutron star matter, it would weigh
A) about 50 pounds. B) as much as the entire Earth. C) about as much as a truck. D) about as much as a large mountain.
It is possible that life exists on orphan planets, even though they do not orbit a star
Indicate whether the statement is true or false
What is the cosmic microwave background?
A. radiation released when neutral atoms formed in the young Universe B. radio noise from Seyfert galaxies C. radiation from the first stars formed when the Universe was young D. radiation from hot gas in intergalactic space
What does Hubble's law tell us?
A) The longer the period of a Cepheid variable, the greater its luminosity. B) The more distant a galaxy, the faster it is moving away from us. C) The faster a spiral galaxy's rotation speed, the more luminous it is. D) For every force, there is an equal and opposite reaction force.