Nova Cygnus 1975
The last bright nova in our galaxy was first seen on August
29th 1975.
The nova when discovered was of the 3rd
magnitude but would reach a magnitude of 1.8 the following day nearly as bright
as Deneb one of the stars of the summer triangle which has a magnitude of 1.3.
The nova was only about 5 degrees from Deneb and for a short period of time
changed the appearance of the constellation of Cygnus.
The nova was visible to
the naked eye for about a week before it faded from view and optical aid was
needed to see it and was about 6,300 light years away and originally
would have been below about magnitude 19, meaning that the star had increased
in brightness by about 40 million times.
Nova Cyg was the second brightest nova
of the 20th century with only CP Puppis in 1942 being brighter.
The term Nova comes from the Latin for New, a few hundred
years ago when astronomers saw what we call Nova they thought they were new
stars being created. A nova is a binary system where two stars orbit each
other. Typically one will be a white dwarf, and the other a red giant, the
white dwarf has a strong gravitational field and pulls gas from the larger
though less massive red giant. When some of this less dense and cooler gas
falls onto the hot surface of the white dwarf it is thrown off into space, the
star will become brighter for a period of time before returning its normally brightness.
This process can happen more than once.
At the time of its discovery it was simply referred to as
Nova Cygni 1975, today it has the designation nova V1500 Cyg, which means it
was the 1500 variable star to have been discovered in the constellation of
Cygnus.
We are clearly due for another bright nova, during the 20th
century 6 novae were seen between
1900-1950 which were at least as bright as the North Star, from 1950-1999 there
was only 1. In the 21st century so far there have been none!
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