An atmosphere is an envelope of gas around a planet, dwarf planet or moon.
Constellations are clusters of related things, especially the stars that form patterns in the night sky — some of which date back to ancient times.
Billions of years of meteorite impacts may have transformed much of Mercury's graphite crust into precious gemstones.
Once known as a pipsqueak planet, Pluto is now the solar system’s best known dwarf planet.
As private companies prepare to sprinkle space with tens of thousands of satellites, experts worry about the mushrooming threat of space junk.
Dark energy is the unknown force causing the universe to expand faster and faster.
Eyelash-like radio filaments accent the brightest feature in this image — a supermassive black hole.
These carbon-based molecules, found in a meteorite, may reflect merely a mixing of water and minerals on the Red Planet over billions of years.
A new sleeping bag could avoid vision problems on long space flights due to microgravity. It counters a fluid buildup behind astronauts’ eyes.