Using the technique of main-sequence fitting to determine the distance to a star cluster requires that ________.
A) we use ultraviolet and X-ray telescopes
B) we have telescopes powerful enough to allow us to identify the spectral types of main-sequence stars of many masses in the cluster
C) the cluster be near enough for us to measure the parallax of its stars
D) we have a well-calibrated period-luminosity relation for Cepheid variable stars
Question 2
The COBE data allow us to test the isotropy of the universe.
Indicate whether the statement is true or false
How genes produce proteins that determine traits in a simple dominant-recessive relationship.
Star-nosed mole
Using Parallax to Determine Distance
The Coma Cluster
Sequence of patient positions for heart auscultation
Three Main Types of Tectonic Plates Boundaries