Black holes are such massive objects that even light, let alone physical matter, is supposed to escape its gravitational pull. Yet at times, jets of radiation and ionized matter are inexplicably spewed out into space. Miller-Jones and his team wanted to investigate how matter is sucked in and expelled from black holes, so they took a closer look at Cygnus X-1.
They observed the black hole for six days using the Very Long Baseline Array, an array of 10 radio telescopes located across North America, from Hawaii to the Virgin Islands. The resolution is comparable to what would be required to spot a 10-centimeter object on the moon, and it’s the same technique as the Event Horizon telescope. take the first photo of a black hole.
Using a combination of measurements involving radio waves and temperatures, the team modeled the precise orbits of the Cygnus X-1 black hole and massive supergiant star HDE 226868 (the two objects gravitate towards one another) other). Knowing the orbits of each object allowed the team to extrapolate their masses – in the case of the black hole, 21 solar masses, which is about 50% more than once thought.
The mass of black holes depends on a few factors, most notably the size of the star that collapsed in the black hole and the amount of mass that is eroded as a stellar wind. Hotter, brighter stars tend to produce more volatile stellar winds, and they also tend to be heavier. Thus, the more massive a star, the more it tends to lose mass by stellar wind before and during its collapse, which results in a lighter black hole.
But in general, scientists believed that the stellar winds in the Milky Way were strong enough to limit the mass of black holes to no more than 15 solar masses, regardless of the size of the original stars. The new findings clearly reverse these estimates.
“Finding a black hole that was significantly more massive than this limit tells us that we need to revisit our models of the mass mass that larger stars lose in stellar winds during their lifetime,” says Miller-Jones. This may mean that the stellar winds moving through the Milky Way are less powerful than we thought, or that the stars are massaging the hemorrhage in some other way. Or it could mean that black holes are behaving more erratically than we can imagine.
The team plans to continue with more sightings of Cygnus X-1. Other instruments, such as the Square Kilometer Array planned in Australia and South Africa, could provide a better view of this black hole and others nearby. There could be between 10 million and one billion black holes in the Milky Way, and studying at least a few more could help unravel this mystery.