Planets, missions, stars and the night sky, explained with numbers you can check.
From the solar system and exoplanets to eclipses, satellites, Milky Way season and space calculators. Every page is built from open data, shows its working, and says what's measured, what's inferred and what nobody knows yet.
Moon
Mars
Solar systemEvery planet, its day, year, gravity and moons, from NASA data.
MissionsEvery Moon and Mars mission ever launched, counted and graded.
ProbesVoyager, Cassini, New Horizons, Webb and the spacecraft that went furthest.
ExoplanetsHow many planets orbit other stars, and what we know about them.
Sky calendarEclipses, planet oppositions and meteor showers, with the Moon worked in.
MysteriesWhat's measured, inferred and unknown about space's open questions.
Space by the numbersSatellite and launch counts, with the definition behind each.- Space calculatorsYour weight, your age and travel times on other worlds.
Milky Way core score by month, Lassen Volcanic National Park, 2027 (out of 100)
When is the Milky Way best?
The chart shows one park, Lassen Volcanic National Park, over one year, 2027. Each wedge is a month, and the longer the wedge, the better the month: more hours with the core above 10 degrees, full darkness, no Moon and little cloud.
The score isn't a forecast. It ranks months and parks, and every page says what it leaves out.
The top six
Let's Explore
- Solar systemEvery planet, its day, year, gravity and moons, from NASA data.
- MissionsEvery Moon and Mars mission ever launched, counted and graded.
- ProbesVoyager, Cassini, New Horizons, Webb and the spacecraft that went furthest.
- ExoplanetsHow many planets orbit other stars, and what we know about them.
- Sky calendarEclipses, planet oppositions and meteor showers, with the Moon worked in.
- MysteriesWhat's measured, inferred and unknown about space's open questions.
- Milky Way seasonBest months and best nights, park by park.
- Space by the numbersSatellite and launch counts, with the definition behind each.
- Space calculatorsYour weight, your age and travel times on other worlds.
How every page is built
- KnownMeasured directly, with the instrument and date.
- InferredWorked out from what was measured, with the reasoning shown.
- UnknownNot settled, with what would settle it.