The hydrogen lines in spectral type A stars

a. are most narrow for supergiants.
b. are most narrow for main-sequence stars.
c. can not be used to estimate the luminosity of the star.
d. are very weak and difficult to see.
e. are useful in determining the apparent magnitude of the star.


a

Physics & Space Science

You might also like to view...

Stars are continually forming in the halo of our Galaxy today

Indicate whether the statement is true or false

Physics & Space Science

A flashlight beam is seen because of

a. specular reflection. b. diffuse reflection. c. dispersion. d. refraction.

Physics & Space Science

Which of the following is a technique that can be used to speed up a spacecraft without the need for extra fuel?

A) a gravitational slingshot, in which the spacecraft gains momentum by flying near a planet B) releasing unnecessary weight after takeoff to make the spacecraft lighter C) flattening after takeoff to make the spacecraft more aerodynamic D) landing on a fast-moving asteroid and relaunching at high speed E) collect material in space that can power the spacecraft

Physics & Space Science

What is the temperature of a system in thermal equilibrium with another system made up of ice and water at one atmosphere of pressure?

a. 0°F c. 0 K b. 273 K d. 100°C

Physics & Space Science