Why can't astronomers use the 21-cm line of neutral hydrogen gas to measure the masses of elliptical galaxies?
A) All elliptical galaxies are too far away for us to detect the 21-cm line.
B) The disorderly motion of the material in elliptical galaxies prevents us from measuring different velocities at different sides of the galaxy.
C) Elliptical galaxies have little gas, so they do not have strong 21-cm line emission.
D) Supermassive black holes in the center of elliptical galaxies disturb measurements of the 21cm line.
C) Elliptical galaxies have little gas, so they do not have strong 21-cm line emission.
You might also like to view...
When the Sun moves off the main sequence, it will initially become a red supergiant
a. True b. False Indicate whether the statement is true or false
A convex mirror has a focal length of ?20 cm. What is the object distance if the image distance is ?10 cm?
a. 10 cm b. 40 cm c. 60 cm d. 20 cm e. 30 cm
Which of the following molecules is polar?
A) a B) b C) c D) All are polar. E) Only A and C are polar.
What can be used to reconstruct the past vegetation of an area and infer environmental conditions
What will be an ideal response?