Monday, 23 January 2017

The Craven Star Party and 83 Ursa Major

The Craven Star Party and 83 Ursa Major

Despite the weather being very cloudy on January 18th over 60 people visited the village hall in Cracoe to hear a series of astronomy talks and meet people from the Earby, Bradford and Keighley astronomical societies and have a thoroughly enjoyable evening.

When not looking for astronomical anniversaries as the astrognome I do when ever possible observe the sky. My great interest was always high latitude novae, these are novae which appear 3-4 kpc above the galactic plane. This means that I tend to look at the less fashionable areas  of the night sky.

I have recently been observing the area around the handle of the plough, it is an area I have watched many times in the past. A star which is of great interest to me is the star 83 Ursa Majoris which  is a spectral class M2 III v  and is officially classed as a semi regular long period variable varying between 4.6- 4.7 and has the designation IQ UMa. There appears to be little information available on
 this star.



On January 20th while observing the star using 15 x 70 binoculars I am a very old fashioned kind of astronomer 83 UMa did not look much brighter than either 81 UMa mag 5.6 or 84 UMa mag 5.7 both are A class stars, in fact 84 UMa is a alpha2 CVn type variable with a very small amplitude.

It should be remembered that the vats majority of red giant stars will vary to some extent as they are approaching the end of their time lines.

According to Miss Agness Clerke it was reported that on August 6th 1868 that 83 Ursa Majoris a  6th magnitude star near  Mizar was seen by the Irish astronomer John Birmingham to be equal to delta Ursa Majoris or Megrez which has a mag of 3.3, though for only that night only. Birmingham went on to say that the star was worth an occasional glance at in the future.

What is of interest is that the 83 UMa was classed as 6th magnitude by Flamsteed in his catalog of 1725 and in 1868 where as today it is around mag 4.5 . I wonder what is going on. As I make more observations I will keep you posted.




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