Answer to Question 1
Cepheid variables are extremely bright variable stars that increase and decrease in brightness in a repetitive cycle. This group of stars is significant because their true brightness, called absolute magnitude, can be determined by knowing the rate at which they pulsate. When the absolute magnitude of a star is compared to its observed brightness, a reliable approximation of distance can be established. Thus, Cepheid variables are important because they can be used to measure large astronomical distances. Hubble observed the Andromeda galaxy, beyond the Milky Way, and used his observations to determine that the universe extended far beyond the limits of our imagination.
Answer to Question 2
It is a medium-sized, middle-of-the-road main sequence star.
Imaginary Thoracic Lines, Left Lateral View
Antibody Structure
DNA detail structure
Structure of the cytochrome b6f complex
The X-ray crystal structure of an S1 fragment of myosin II
Divided View