Stellar parallax (61 Cygni)

What was discovered

Bessel measured the parallax of 61 Cygni (0.31 arcseconds) and obtained a distance of about 10 light-years. First direct measurement of the distance to a star and definitive proof of the Earth's motion.

Henderson (Alpha Centauri) and Struve (Vega) measured parallaxes at almost the same time; Bessel published first.

What it led to

• Scale of cosmic distances
• Definition of the parsec
• Absolute luminosities and the H-R diagram

Built on

• Stellar proper motion1718
• Aberration of starlight1729

Made possible

• Alpha Centauri's parallax (Henderson)1832-1839
• Discovery of Sirius B1862
• Hertzsprung-Russell diagram1911-1913
• Precision heliometer

📄 Original publication

Links

Sources✓ verified 2026-09-25

• https://en.wikipedia.org/wiki/Friedrich_Bessel