How to See the Planets With the Naked Eye
Five planets are bright enough to spot with nothing but your own eyes — the trick is knowing when to look, where to look, and how to tell a planet from an ordinary star.
Read guide →Solar System Guides
Original, in-depth explainers — how to observe the planets, the moons that might harbour life, how orbits work, the true scale of it all, and what lies at the edge of the Solar System.
Why Mars Is Humanity's Next Frontier
Mars offers a day nearly like our own, ice and air that could sustain a mission, and clear evidence it was once warm and wet — wrapped in radiation, cold, and distance that make it the hardest frontier humans have ever tried to reach.
Read guide →Jupiter's Galilean Moons: Io, Europa, Ganymede & Callisto
Four points of light that Galileo mistook for stars in January 1610 turned out to be a volcanic inferno, a hidden ocean, the largest moon in the solar system, and an ancient, battered relic — and a fleet of spacecraft is now converging on all four.
Read guide →Ocean Worlds: The Search for Life on Europa, Enceladus & Titan
Three moons far from the Sun hide the ingredients for life — liquid water, chemical energy, and organic chemistry — and two NASA spacecraft are already on their way to find out how far those ingredients go.
Read guide →Planetary Rings: Saturn and the Other Ringed Worlds
Saturn's rings are the showpiece of the Solar System — but all four giant planets wear them, and even a few tiny worlds do too.
Read guide →Dwarf Planets Explained: Why Pluto Was Reclassified
In August 2006, astronomers voted to strip Pluto of planethood, not because it had changed, but because a new discovery beyond its orbit had exposed how badly the old, informal rules for calling something a planet had aged.
Read guide →The Asteroid Belt: What's Really Between Mars and Jupiter
Hollywood imagines a boulder field so dense that starships have to dodge debris every second; the real asteroid belt is so sparse that more than a dozen spacecraft have flown straight through it without ever coming close to hitting anything.
Read guide →Comets: Cosmic Snowballs and How to Spot One
A comet is little more than a chunk of ancient ice and dust, but when the Sun starts to cook it, that chunk can grow tails millions of kilometers long and become one of the most striking sights in the night sky.
Read guide →The Edge of the Solar System: Kuiper Belt, Oort Cloud & Beyond
Neptune is not where the Sun's domain ends — beyond it lies a belt of icy dwarf worlds, a scattered swarm of exiled comets, and a hypothetical shell of debris that may stretch nearly halfway to the next star, so that "the edge" means something different depending on whether you're asking about wind, gravity, or geography.
Read guide →How Orbits Work: The Motion of Planets Explained
Every planet is falling continuously toward the Sun and continuously missing it, and the precise geometry of that endless miss was worked out four centuries ago by a German mathematician staring at Mars.
Read guide →How Big Is the Solar System, Really?
Miles and kilometers stop meaning much once you leave Earth, so astronomers measure the solar system in light and in absurdity — in minutes sunlight needs to reach a planet, and in how laughably tiny the planets look once you shrink the Sun down to something you could palm.
Read guide →Anatomy of the Sun: How Our Star Works
The Sun fuses 600 million tons of hydrogen every second, and the layers carrying that energy from its crushed core to a corona hotter than the surface below explain nearly everything it does to the rest of the solar system.
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