BEIJING -- Astronomers have reported new observations on the first black hole ever detected, according to research published on Friday.

Astronomers at the National Astronomical Observatories (NAOC) under the Chinese Academy of Sciences cooperated with researchers from the United States and Australia and reported the discovery in three papers published in the Science and Astrophysical Journal.

The black hole system, Cygnus X-1, contains a stellar-mass black hole with a 21 solar mass that rotates at a speed close to the speed of light, according to the study.

Cygnus X-1 is one of the closest black holes to Earth. It was discovered in 1964. In 2011, astronomers accurately measured the distance and mass of Cygnus X-1 for the first time.

In the latest study, astronomers used the Very Long Baseline Array, a system of 10 radio telescopes located in the United States, together with a clever technique to re-measure the black hole's distance from Earth -- 7,240 light-years.

With the latest distance data, researchers re-estimated the mass of Cygnus X-1. It was found to be 21 times the mass of the Sun, a 50 percent increase from previous estimates.

"Using the updated measurements for the black hole's mass and its distance away from Earth, we were able to confirm that Cygnus X-1 is spinning incredibly quickly, very close to the speed of light and faster than any other black hole found to date," said the NAOC's Gou Lijun, one of the authors of the study.