Look up. Then understand.
Planets you can compare, star patterns you can find, a Moon that is honest about its phase, and a primer that does not talk down to you. Built to be read tonight and remembered the next time the sky is clear.
Rooms in the observatory
Each section stands on its own. Follow whichever one you're curious about today.
The Planets
All eight worlds with real numbers — size, distance, orbit, moons. Includes a true-to-scale switch that shows just how enormous Jupiter really is.
Constellations
Sixteen star patterns drawn from real star positions, each with the myth behind it and the season you can actually spot it.
Moon Phases
Tonight's phase, calculated live from the lunar cycle. Pick any date in history or the future and see exactly what the Moon looked like.
Learn
Eight ideas that hold the rest of astronomy up: light, gravity, stars, planets, galaxies, life, the Big Bang, and how to actually look.
Facts
Fifty genuinely strange facts about space, filterable by topic — solar system, stars, galaxies, travel, life and physics.
Quiz
Four levels from Stargazer to Astronomer. Pass one to unlock the next, and keep a rank in the header when you earn it.
Beast
Ask about a planet, a constellation, tonight's Moon, or NASA's picture of the day. Answers come from the same data the rest of the site uses.
The numbers that don't fit in your head
Space is mostly the distance between things. These four are worth sitting with.
1.3 million
Earths would fit inside the Sun. And the Sun is an average star — there are far larger ones in our own galaxy.
4.24 light-years
To Proxima Centauri, the nearest star after the Sun. Voyager 1, our fastest probe, would need roughly 73,000 years to get there.
100 billion
Stars in the Milky Way, give or take. And roughly two trillion galaxies in the observable universe.
93 billion ly
Across the observable universe. Space expanded, so the edge is farther than the universe is old in years.
5,500+
Confirmed planets around other stars, and the count is still climbing every observing season.
Start with the planets
Every planet on the next page is drawn entirely in CSS — the bands on Jupiter, the rings of Saturn, the ice caps on Mars. No images were downloaded to make them.