Scientists made waves last year after announcing the invention of a "monster black hole," unlike anything seen before. Black holes that form when a star collapses under the influence of its own gravity, are usually about 20-30 times the mass of our sun. So it was breaking news when, in November 2019, scientists led Jifeng Liu of the National Astronomical Observatory of China (NAOC) of the Chinese Academy of Sciences, reported the invention of a black hole 70 times as massive as our sun.
This would have been the most massive black hole ever discovered (by far) — a groundbreaking finds that would have drastically changed our perception of these objects. However, following this work, a number of scientists questioned these findings as they seemed improbable. In fact, there were a handful of studies that found evidence that completely disproved the possibility of such a black hole.
Studies Disproving Possibility Of Ultramassive Black Hole
The strangest black holes in the universe. In December 2019, Kareem El-Badry, an astronomy doctoral student at the University of California, Berkeley, co-wrote a paper published online in the preprint server arXiv providing evidence that this wasn't a 70 solar mass black hole. (The paper was later published in the Monthly Notices of the Royal Astronomical Society.) Around the same time, two additional papers disproving the discovery were published on arXiv: one from a team led by J.J. Eldridge, a theoretical astronomer at the University of Auckland in New Zealand, and another led by Michael Abdul-Masih, a Ph.D. student from the KU Leuven Institute of Astronomy in Belgium. An artist's depiction of the giant stellar-mass black hole suspected by some researchers to be in the binary system LB1 accreting gas from a nearby blue companion star. during a number of studies, researchers have disproven the probability that the black hole in LB1 is ultramassive.
(Image credit: YU Jingchuan, Beijing Planetarium, 2019)
On Wednesday (April 29), Abdul Masih's paper was published in the journal Nature. In this paper, the team analyzed the system in-depth and concluded that there is "no evidence for a massive black hole," they wrote in an accompanying commentary.
That same day, Liu's team responded with their own Nature commentary in which, while they disagree with some points made by other researchers, but they are doing agree that there's no 70 solar mass black hole within the system.
70 Solar Mass Black Hole In A Binary System
Resuteam originally found the object in question when they discovered the binary, or two-object system LS V +22 25 (or LB-1 for short), which they described in a peer-reviewed study published Nov. 27, 2019 in Nature. They described a system with a 70 solar mass black hole and an 8 solar mass star orbiting each other. The star, because it was bright and obvious, was easy to spot. But the alleged monster black hole? Not so much. Usually, in systems with stellar-mass black holes, there is a bright, X-ray emission shooting out of the system that scientists can use to identify it. This emission line is created when a black hole accretes, or pulls material from the other object (in this case a star) in the system. But since LB-1's black hole doesn't accrete material from its partner star, it doesn't create an X-ray emission line, Liu's team found. This made it a little trickier to study.
So, to identify the second object in the system the team had to rely on a more subtle signature known as an H-alpha emission line. This is a spectral line or a dark line in an object's the observed light spectrum that can be used to identify which molecules or atoms make up the material it's coming from.
Liu's team presumed that this H-alpha emission line was coming from an accretion disk or disk of gas and mud that the black hole pulls in from other objects around the black hole. By observing how this emission line appeared to wobble, they determined the orbital rotation and therefore the size of the black hole. But the interpretation of this subtle wobbling signature, this H-alpha emission line which led Liu's team to work out the existence and large size of a black hole.
Is That The Main Finding Other Researchers Have A Drag With
"No monster black hole" The three papers published initially to the preprint server arXiv in 2019 in response to Liu's alleged discovery found that the movement of this faint H-alpha emission line was actually a kind of optical illusion and that the orbital motion Liu's team calculated to determine the black hole's size was inaccurate.
"Instead of the wobble coming from the black hole, they found it was more likely a consequence of the orbital motion of the subgiant [its star], thus completely reducing the mass of the black hole," Jackie Faherty, a senior scientist at the American Museum of Natural History in New York and a co-host of "StarTalk Radio," who wasn't involved in any of these papers, told Space.com in an email.
In their paper, Abdul-Masih's team used observations they have made using the Flemish Mercator telescope at La Palma in the Canary Islands over the last three months (or since their last paper on this subject) and have "found that that the signal that they use to measure the mass of the black-hole was actually fake," co-author and Hugues Sana, a research associate professor at KU Leuven, told Space.com in an email. Sana added that, in this paper, Abdul-Masih "showed that the same apparent signal is produced by the motion of the spectral line of the visible B-star companion." So, Sana explained, "once we take under consideration the motion of the B-type star spectrum, the signal wont to calculate the High Mass of the (putative) black hole disappears and no indication of a high-mass black hole is left within the data."
To summarize their main finding, "We show that this complicated emission line is contaminated by an absorption line associated with the star, which Liu and his team didn't account for," Abdul-Masih told Space.com in an email. But Abdul-Masih's team didn't just find more evidence to prove that this object isn't a 70 solar mass black hole. They even have a far better idea of what may very well be within the LB1 system.