Constellations are clusters of related things, especially the stars that form patterns in the night sky — some of which date back to ancient times.
Once known as a pipsqueak planet, Pluto is now the solar system’s best known dwarf planet.
The Doppler effect is a perceived change in the frequency of light or sound waves due to the wave source moving relative to an observer.
Dark energy is the unknown force causing the universe to expand faster and faster.
The force of gravity holds us on the ground, keeps planets in orbit and extends throughout space. A very weak gravitational pull is called microgravity.
Different kinds of telescopes on Earth and in space help us to see all wavelengths of light. Some can even peer billions of years back in time.
The spiral-shaped Whirlpool galaxy may be home to the first planet spotted outside our own Milky Way galaxy.
Meteor showers happen when Earth’s orbit passes through trails of debris left behind by comets or asteroids.
These observations offer some of the best evidence yet that planets around other stars have moons, or exomoons.