1. What is parallax?
Parallax is an apparent displacement in the apparent position of an object viewed along two different lines of sight. It is measured by the angle or semi-angle of inclination between those two lines. Objects that are closer to the solar system have a larger parallax than those that are far away, so parallax can be used to estimate celestial distances.
2. What is luminosity?
Luminosity is the total amount of power that a star emits into space.
3.How do we measure stellar luminosities?
We measure stellar luminosities through the Inverse Square Law for Light.
4. How do we measure stellar temperatures?
Color, temperature, and spectral type. Spectra of stars show that their surface temperature ranges from more than 40,000 K to less than 3,000 K, responding to the sequence of spectral types of OBAFGKM.
5. What is a Hertzsprung-Russell diagram?
A Hertzsprung-Russell diagram plots the surface temperatures of stars against their luminosities.
6. What is the significance of the main sequence?
Most stars are main sequence stars, which shine by fusing hydrogen into helium in their cores.
7. Who was Ejnar Hertzsprung?
A Danish astronomer born in Copenhagen. In 1913 he determined the distances to several Cepheid variable stars. Helped to create the Hertzsprung-Russell diagram and discovered two asteroids.
8. Who was Henry Norris Russell?
An American astronomer born October 25, 1877. Helped to develop the Hertzsprung-Russell diagram and the Russell-Saunders coupling, also known as LS coupling. He studied at Princeton University and co-wrote Astronomy: A Revision of Young's Manual of Astronomy.
9. What is the mass of Betelgeuse?
20 x the mass of the Sun.
10. What is the parallax of Sirius?
0.38"
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