The North Star (Polaris) is useful because:

Dark matter has been directly observed with telescopes. 

The time it takes Earth to orbit the Sun once is called a

The Andromeda Galaxy is moving toward the Milky Way. 

Mars has liquid water lakes on its surface today. 

Stars spend most of their lives in the main sequence phase. 

Radio waves travel faster than visible light. 

One day on Earth is defined by:

The James Webb Space Telescope observes mainly in radiowaves. 

What remains after a supernova of a very massive star?