Friday, 23 October 2020

John Goodricke, Delta Cepheus and the Distance to the Galaxies


John Goodricke, Delta Cepheus and the Distance to the Galaxies

John Goodricke who was deaf was on one the fathers of variable star astronomy. He worked with Edward Pigott in the city of York between 1781 and 1786 when he died at the tragically young age of 21.

Goodricke and Pigott explored the sky they explained that the variations of the star Algol in the constellation of Perseus were caused by an unseen body eclipsing Algol. The same principal is used by astronomers today to look for planets orbiting other stars. They then went on to both discover a new variable star on the same night, the 10th September 1784, Pigott discovered eta Aquila and Goodricke discovered beta Lyra. I described this as a night to remember in york.

The indefatigable Goodricke then went onto to discover the variability of the star delta Cephei in the constellation of Cepheus the King on the night of October 23rd 1784. This was to prove to be one of the most important astronomical discoveries.

Delta Cepheus is of tremendous value to astronomers today, Goodricke could not know the importance of his discovery. Cepheid variable stars are used to work out the distance to other galaxies. It was in 1912 that Henrietta Leavitt working at Harvard realised that there is a relationship between the Cepheid variable stars a pattern was seen that the brighter ones seem to have longer periods and that Cepheids were very luminous stars and there was a relationship between the periods and distance.

If Cepheids could be found in other galaxies the distances could be worked out. They were and this allowed astronomers to work out how far away the galaxies were. This was down to the discovery of delta Cepheus in 1784 by the deaf astronomer John Goodricke the discovery of this relation with the cepheids in 1912 by Henrietta Leavitt who was also partially deaf. This relationship is known today as the Period Luminosity Relationship.

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