Hipparchus

(190 - 120 BC)

Hipparchus was a Greek astronomer who lived between 190-120 B.C. He created the first accurate star map and kept a catalogue of over 850 stars with their relative magnitudes.

The system of epicycles describing planetary motion was developed by Hipparchus, and helped preserve the geocentric model of the universe. His estimates of the moon's size and distance relative to Earth were also remarkably accurate for his time.

Hipparchus is considered the founder of trigonometry for his work with the lengths of chords traced out by angles in a circle. His table of chords was the forerunner to modern trig tables.

**The preceding information is provided by the University Corporation for Atmospheric Research's Windows to the Universe.**