Thursday, 25 September 2014

Astronomy Scrapbook Thursday 25th September 2014

September 25th 1795 discovery of R CrB

R CrB
25th September 1795 The Sooty Star

This star now known as R CrB was discovered to variable by Edward Pigott while living in the city of Bath.

Pigott had worked with John Goodricke in the 1780s in York where they became the ‘Fathers of Variable Star Astronomy’.  After Goodricke`s death in 1786 Pigott move to Bath to continue his astronomical work.

R Crb is the prototype of a small class of rare variables stars that remain at maximum brightness and then suddenly and unexpectedly fade from sight. When R Crb is at its brightest it can easily be seen with binoculars. Then it will begin to fade in brightness for a few weeks until binoculars are not powerful enough to find it and a telescope is required to see the star.


It is believed that clouds of carbon form around the star, then condenses and blocks the light as it turns into a ‘soot cloud’. Later when the cloud clears the star returns to its normal brightness, until  the next time.

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