S Delphinus observed from Manchester by Mr Baxendell

Mr Baxendell who came from Manchester read a communication on the variable star S Delphinus at the meeting of the Literary and Philosophical Society of Manchester on the 9^th November 1865. The report stated that he had seen the maximum brightness occur on August 9^th 1865 with a magnitude of brightness of 8.9, the average period between maximum brightness being 332 days and the minimum brightness being magnitude 13.5.

Mr Baxendell’s results were confirmed by Mr G Knott of Cuckfield. The colour of the star seen was reddish and is a more intense red colour as it approached its minimum brightness.

Note:- Today S Delphinus is known as a Mira type red giant variable star with a magnitude range of 8.3-12.4. The star returns to brightest every 277 days and lies about 2,700 light years away and its spectral class in between M5 – M8. It cannot be seen with the naked eye you would need a telescope to see it.

The Mira class of stars were first identified by the Dutch astronomer David Fabricius in 1596 when he saw a fairly bright star in the constellation of Cetus the Whale.

In 1603 the German astronomer Johann Bayer saw this star and in his Uranometria star atlas he allocated it the Greek letter Omicron. In his system the brightest star in each constellation was given the Greek letter alpha, the second brightest beta and so on through until omega the 24^th and the last letter in the Greek alphabet and the faintest star that can be represented under this system.

I should point out that this system does not always work according to plan, because sometimes alpha is not the brightest star in a constellation.

In the following years astronomers noted that omicron Cetus changed in brightness and sometimes could not even be seen with the naked eye. As this was the first time that this had been noted by astronomers the star was given the name of Mira which in Latin means the Wonderful

I don’t think that Joseph Baxendell discovered the variability of S Delphinus, but he was one of the earliest observers of this star. As the star is not one of the brightest of the Mira class of stars I am not t sure how much it is observed today. All that being said though, the fact that Baxendell saw S Delphinus  just goes to show how good an observer he actually was.

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