It’s fair to say that the weather at least in the north of England has not been fantastic this summer, for looking at the stars anyway. Even the weather for the Perseid meteor shower was poor despite the weather forecasts saying it should be clear, Things finally changed right at the end of August with some clear nights.
I was able to get back to searching for high latitude novae,
these are stars 3 or 4 kilo parsecs above the galactic plane. I was quickly
looking at some of my old stomping grounds including the area around the
Plough. The star Fl 83 Uma on my photograph was particularly red looking on
August 29th, 2024. That is nothing surprising as it is an M2 III red
giant star. It’s one I always look out for as it does have some interesting
history. The following night August 30th it was not as red.
The Fl letters in front of the number 83 indicates that the
star was the 83rd one listed in
Ursa Major by John Flamsteed the first astronomer royal in his star catalogue
which was published in 1725.
On August 6th, 1868, John Birmingham saw the star
for one night only become much brighter than normal. Its usual magnitude is 4.6
but, on that night, Birmingham said it was as bright as Megrez in the handle of
the blade of the Plough. Megrez has a magnitude of 3.3. I know there are some
suspicions that Megrez might be some kind of very long period or secular type
variable. Birmingham would go on to produce an important catalogue of red
stars.
John Birmingham’s observation was interesting none the less,
my observations of 83 UMa go back to
last century, but I have never seen
anything untoward.
John Birmingham was an important Irish astronomer of the 19th
century for reasons other than 83 Uma. I am not writing a history of the life
of John Birmingham people with far greater skill than I can do that. In 1866
Birmingham saw a star in the constellation of Corona Borealis or the Northern
Crown we now call T CrB. This star was a nova.
A nova is a binary system of two stars one a small hot white
dwarf the other a large cooler giant star. The white dwarf pulls gas from its
larger companion towards it and this gas then forms a disc around the white
dwarf. This theoretical area is known as a roche lobe. When the lobe is full of
cool gas it cascades down onto the hot surface of the white dwarf where the
star essentially sizzles like a very hot pan. A small amount of gas is thrown
away into space. In medieval times when people saw these stars appear they
called the nova, because this is the Latin word for new. They thought these
stars were being born. They are not, they are much older stars just going
through a phase of their evolution. Although an old term we still use the word
nova today to explain the process we see.
Then incredibly T CrB went nova again in 1946 and it
acquired the name of the ‘Blaze Star’. Although not unique it certainly was the
brightest nova to do so. Today I think there is an acceptance among astronomers
that stars are seen to go nova will do so again.
Maybe like yourselves I have been bombarded all year long
with circulars and news reports telling me that T CrB was going to go nova
again this year. The period between 1866 and 1946 is 80 years but the experts
have suggested that T CRB was winding up to go nova this year, although nothing
has happened yet, we may have to wait for the 80-year period to go by making
the next event in 2026. We will see.
And finally, as in all good astronomy stories John
Birmingham acquired a telescope in 1869 it was not any old telescope, but it
was a 4.5-inch telescope made by Thomas Cooke & Sons of York.
As autumn and winter approach I will hope to get back to my
photography, weather permitting of course and checking for high latitude novae
and keeping an eye on amongst other stars, 83 Uma.
www.theramblingastronomer.co.uk
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