Labelling Stars

14.2 - Be able to use the Bayer system for naming the brightest stars within a constellation

On star maps, brighter stars appear as a larger dot and smaller stars as a smaller dot.

Stars are labelled according to their brightness. The system that astronomers use is the Bayer Designation, named after the German astronomer Johann Bayer who in 1603 catalogued stars by using the Greek alphabet to represent their brightness where Alpha is the brightest, Beta the next brightest etc.

With this system the brightest star in Orion is Alpha Orionis.

When Bayer had used all the 24 letters he started using lower case Latin letters (our alphabet).

It is in use today but has been amended over time by the International Astronomy Union.

Some criticism of the system is that it does not take into account changes in the brightness of stars due to variability or that the Alpha star is sometimes not the brightest star. Changes in constellation boundaries have led to some confusion. The top right star of the square of Pegasus is Alpha Andromedae.

Amongst other ways to label stars are Flamsteed numbers which number stars by their brightness.


Example of Orion: Bayer made designations not just by brightness but also moved top to bottom


Explain how stars are labelled in a constellation

Most Used Greek Letters

Most used

α Alpha
β Beta
γ Gamma
δ Delta
ε Epsilon

Did you know?

A celestial cartographer or map maker was also known as a uranographer

Links Greek letters