Astronomy facts
One short astronomy fact per day, each with a figure and a source. Pick a topic or scroll back through the days.
April 2025
- Apr 19 Dwarf Planets & Small BodiesA Comet’s Tail Always Points Away from the Sun
- Apr 18 Dwarf Planets & Small BodiesHalley’s Comet Will Return in 2061
- Apr 17 Dwarf Planets & Small BodiesComets Might Have Brought Water to Earth
- Apr 16 Dwarf Planets & Small BodiesComets Can Have Two Tails (or More)
- Apr 15 Night SkyThe Faint Unicorn Constellation Dates to 1612
- Apr 14 Night SkyThe Stars in a Constellation Aren’t Actually Close to Each Other
- Apr 13 PlanetsNeptune’s Atmosphere Cooled Then Warmed for Unknown Reasons
- Apr 12 PlanetsUranus Rolls Around the Sun on Its Side
- Apr 11 PlanetsNeptune’s Winds Are the Fastest in the Solar System
- Apr 10 GalaxiesThe Farthest Thing We’ve Ever Seen Is a Galaxy From the Dawn of Time
- Apr 9 SunThe Sun’s Core May Spin Faster Than Its Outer Layers
- Apr 8 The UniverseAn Unexplained Radio Source Bursts Toward the Galactic Center
- Apr 7 PlanetsA Day on Mercury Has Two Sunrises
- Apr 6 MoonA Mirror on the Moon Helps Us Measure Its Distance
- Apr 5 Missions & SpacecraftThe Fastest Thing Ever Made by Humans Is a Space Probe
- Apr 4 PlanetsThe First Exoplanet Was Discovered Around a Dead Star
- Apr 3 MoonThe Moon Rings Like a Bell
- Apr 2 Night SkyThe Best Time to Stargaze Isn’t Always at Midnight
- Apr 2 PlanetsThe Great Red Spot Is Shrinking
- Apr 1 The UniverseThe Universe Is Missing Most of Its Matter
March 2025
- Mar 28 StarsA Single Spoonful of Neutron Star Material Weighs as Much as a Mountain
- Mar 27 SunThe Sun Will One Day Swallow Earth (But Not for a While)
- Mar 26 StarsA Magnetar Once Blasted Earth with a Gamma-Ray Flare
- Mar 25 PlanetsThe Other Planets Nearly Fit Between Earth and the Moon
- Mar 24 The UniverseSpace Can Expand Faster Than Light
- Mar 23 MoonThe Dark Side of the Moon Isn’t Always Dark
- Mar 22 Dwarf Planets & Small BodiesPluto Has Ice Mountains as Tall as the Rockies
- Mar 21 PlanetsYou Weigh Less at the Equator Than at the Poles
- Mar 20 PlanetsJupiter Has the Deepest Ocean in the Solar System (But It’s Not Water)
- Mar 19 The UniverseNeutrinos Pass Through You by the Trillions
- Mar 18 AstronautsYou Could Survive 15 Seconds in Space (But You Shouldn’t Try)