Cygnus X1 position 19565n3504. Black hole region in Cygnus.
by John Fletcher F.R.A.S. Mount Tuffley Observatory.
Go To Image of Cygnus X1 field.
Slightly less than 0.5 degrees E.N.E. of eta Cygni lies the 9th magnitude star HDE226868. Accurate measurements
show that the position of this star is one of the strongest sources of X ray energy known and is a most convincing
candidate for a Black Hole. HDE226868 is a very hot super giant star of spectral type B.O. with a surface temperature
of 30.000°K. It is a spectroscopic binary and it has been established that very strong heated streamers of
gas, (where the X ray energy originates) are passing from the B star to an unseen component which orbits the visible
star. It is believed this component is a small super dense component of less that 100 miles in diameter.
It is interesting to note that to achieve this "black hole" state based on the Schwarzschild formula
of 1916, the mass of one Sun would have to be compressed down to a sphere 3.6 miles in diameter and the Earths
Schwarzschild radius would be under one centimeter. However a star of greater mass than 3.2 Suns is needed to produce
a black hole. Such a star that has gone supernova and has left a neutron star and a further gravitational collapse
of the neutron star leaves an invisible area where gravity is so strong that not even light can escape its pull.
HDE226868 can easily be seen in the smallest of optical aid and the thoughts that may pass through one's mind whilst
looking at it may leave you wondering what mysteries and secrets the universe holds.
Clear Skies John.