Tuesday 1 March 2022

Rambling around Ursa Major 1


If you look close to Beta Uma or Merak one of the pointers you will see a star Flamsteed (Fl) 38 Uma then nearby a small triangle formed by the stars Fl 39,40,41 Uma.

On closer inspection it will be noted that stars 40 and 41 are to faint to be seen with the naked eye anf yet they have Flamsteed numbers.

Although Fl 40 is shown on the Star Atlas 2000 it is not listed in the Catalogue 2000 as Fl 40 but rather as HD 93075 (The HD stands for Henry Draper). It is listed in most catalogues with a magnitude of 7.1.

 This of course is below the limit of naked eye visibility. Although Flamsteed lists it as being of the 6th magnitude. So unless Flamsteed used some sort of optical aid when he was studying Ursa Major there is no way that he could have seen this star. Now of course it is possible that the star has faded in brightness. There is a variation in the spectral class of the star in catalogues, ranging from F0v to A8v.

Just for good measure Fl 41 which is listed with a magnitude of 6.3 again below the limit of naked eye visibility. The star being reported with a spectrum class of M1 III. As a very large number of red giants are variable I would not be at all surprised if this star varied. The General Catalogue of variable and suspected variables however does not list this star.

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