Astronomers have revisited the first black hole of stellar mass ever identified and have discovered that it is at least 50 percent more massive than we thought.
The black hole in the Cygnus X-1 X-ray binary system has been recalculated to have 21 times the mass of the Sun. This makes it the most massive black star mass hole ever detected without the use of gravitational waves and forces astronomers to rethink how black holes form.
Cygnus X-1 was first discovered as an X-ray source in 1964, and its black hole state became the subject of a bet between astrophysicists Stephen Hawking and Kip Thorne.
Scientists later validated the black hole’s interpretation of the nature of the object, concluding that the X-ray emission was produced by the black hole that struck a binary companion.
It has become one of the most studied black holes in the sky and astronomers thought it was pretty well understood: an object about 6,070 light-years away, with a mass of 14.8 solar masses and a supergiant blue binary companion. called HDE 226868 at approximately 24 solar masses.
According to new observations, we were wrong.
Astronomers have made new parallax observations of the system, observing how it appears to “oscillate” in the sky as the Earth orbits the Sun, using the Very Long Baseline Array, a collection of radio telescopes acting together as a continental-sized collector’s dish.
Ultimately, his observations showed that Cygnus X-1 is at a much greater distance than we thought. This means that the objects themselves are significantly larger.
“We used radio telescopes to make high-precision measurements of Cygnus X-1, the first black hole ever discovered,” explained astronomer James Miller Jones of the International Center for Radio Astronomy Research (ICRAR) in Australia.
“The black hole is in a few days’ orbit with a massive accompanying star. For the first time following the orbit of the black hole in the sky, we have refined the distance to the system, placing it more than 7,000 light-years from Earth. .
“This meant that the black hole was more than 20 times the mass of our Sun, making it the most massive black hole of stellar mass ever discovered without the use of gravitational waves. This challenges our ideas about how massive stars evolve to form black holes. “
Previously, the most massive electromagnetically detected black star mass hole was M33 X-7, which had 15.65 times the mass of the Sun. At the time of its discovery, even the M33 X-7 challenged our black hole formation models.
The scientists concluded that as the massive star that would collapse to form the black hole would reach the end of its life, it would lose much more slowly than the models suggested. They believe something similar for Cygnus X-1.
“Stars lose mass in their surrounding environment due to stellar winds blowing from their surface. But to make such a heavy black hole, we need to mark the amount of mass that bright stars lose during their lifetime,” said theoretical astrophysicist Ilya Mandel of the ARC Center of Excellence in Gravitational Wave Discovery (OzGrav) in Australia.
The precursor star of the black hole Cygnus X-1 would have started around 60 solar masses, ripping out its outer material before the nucleus probably collapsed directly into the dense object it is today, preventing a supernova explosion.
Now, he is locked in an incredibly close, 5.6-day orbital dance with his supergiant blue companion, who now also has a revised mass, which will take him to a mass of 40 solar masses.
This is massive enough that one day it ends up as a black hole, forming a binary black hole similar to those seen in fusions that generate gravitational waves.
However, the binary is unlikely to merge soon. The refined distance measurement will also allow astronomers to recalculate other features of Cygnus X-1. In a separate paper, astronomers found that it rotates almost as fast as the speed of light. This is faster than any other black hole ever measured.
This contrasts directly with gravitational wave binaries, which have very slow or misaligned turns. This suggests that Cygnus X-1 followed a different evolutionary path from the black hole binaries we have seen merge.
Given the distance between Cygnus X-1 and HDE 226868, researchers have calculated that the pair is unlikely to merge within a time scale equal to the age of the Universe: 13.8 billion years.
Studying the system now, before the second collapse of the black hole occurs, presents a rare opportunity to understand the binary of the black hole.
“Observations like these tell us directly a lot about possible evolutionary pathways in making double black holes, some of which have been regularly found in ground-based gravitational wave detectors like LIGO and Virgo,” said physicist Ashley Ruiter from the University of New South Wales Canberra, Australia, who did not participate in the research.
“It’s great that we can still catch the binary ‘in action’ with electromagnetic light before it forms a double black hole: it helps perfect our theories about narrow binary star evolution.”
The team’s research has been published in Science.