Follow your curiosity

What discovery has been shared with you?

FACTREE gives you something interesting to discover every day — and something worth talking about together.

Start with one fact. Explore it, go deeper, then follow whichever branch catches your imagination.

Choose subjects for a surprise

Exploring any topic

Begin your discovery

Your next discovery is one click away.

Choose one or more subjects above, or leave Any Topic selected and let curiosity decide.

Astronomy

Astrometry: Precise Measurement of Star Positions and Motions

Quick fact

The Gaia space telescope measures the positions of nearly two billion stars to an accuracy of 0.00001 arcseconds—equivalent to measuring the width of a human hair from 1,000 kilometers away.

Why this is interesting

When you look at the night sky, the stars appear fixed and unchanging—but they are actually moving across vast distances. How do astronomers measure these tiny, slow motions with incredible precision?