WASHINGTON (Reuters) - A fresh examination has revealed new details about the first black hole ever detected - which was spotted in 1964 and became the subject of a friendly wager between renowned scientists - including that it is bigger than previously known.

Researchers said on Thursday that new observations of the Cygnus X-1 black hole, orbiting in a stellar marriage with a large and luminous star, showed it is 21 times our sun's mass, about 50% more massive than previously believed.

While it is still one of the closest-known black holes, they found it is somewhat farther away than previously calculated, at 7,200 light years - the distance light travels in a year, 5.9 trillion miles (9.5 trillion km) - from Earth.