Question

which statement correctly describes variable stars? variable stars with longer periods have higher luminosities, so they can only be observed when they are close. variable stars with shorter periods have higher luminosities, so they can be observed when they are farther away. variable stars with longer periods have higher luminosities, so they can be observed when they are farther away. variable stars with shorter periods have higher luminosities, so they can only be observed when they are close.

Explanation:

Variable stars follow the period - luminosity relation. Longer - period variable stars have higher luminosities. Higher - luminosity stars can be detected from greater distances.

Answer:

Variable stars with longer periods have higher luminosities, so they can be observed when they are farther away.