"Evidence for this 'direct-collapse' scenario has been emerging recently, but our study arguably provides one of the most direct indications. "The star that formed the black hole in VFTS 243 appears to have collapsed entirely, with no sign of a previous explosion," explains Shenar. Astronomers believe that a stellar-mass black hole forms as the core of a dying massive star collapses, but it remains uncertain whether or not this is accompanied by a powerful supernova explosion. The discovery also allows the team a unique view into the processes that accompany the formation of black holes. But I could not find a plausible explanation for the data that did not involve a black hole," explains El-Badry. "When Tomer asked me to double-check his findings, I had my doubts. The skepticism was shared by CfA co-author El-Badry, whom Shenar calls the "black hole destroyer." A recent Harvard Magazine story similarly calls El-Badry a "black hole debunker." "As a researcher who has debunked potential black holes in recent years, I was extremely skeptical regarding this discovery," says Shenar. "I was very excited when I heard about VFTS 243, which in my opinion is the most convincing candidate reported to date." "For more than two years now, we have been looking for such black-hole-binary systems," says co-author Julia Bodensteiner, a research fellow at ESO in Germany. The newly found black hole is at least nine times the mass of the Sun, and orbits a hot, blue star weighing 25 times the Sun's mass.ĭormant black holes are particularly hard to spot since they do not interact much with their surroundings. "It is incredible that we hardly know of any dormant black holes, given how common astronomers believe them to be," explains co-author Pablo Marchant of KU Leuven. The discovery was made thanks to six years of observations obtained with the European Southern Observatory's (ESO's) Very Large Telescope (VLT). The black hole is "dormant" if it does not emit high levels of X-ray radiation, which is how such black holes are typically detected. In a binary, a system of two stars revolving around each other, this process leaves behind a black hole in orbit with a luminous companion star. Stellar-mass black holes form when massive stars reach the end of their lives and collapse under their own gravity. The work was published today in the journal Nature Astronomy.
Though other similar black hole candidates have been proposed, the team claims this is the first "dormant" stellar-mass black hole to be unambiguously detected outside of the Milky Way galaxy. "We identified a needle in a haystack," says Shenar. The team found that the star that gave rise to the black hole vanished without any sign of a powerful explosion. "For the first time, our team got together to report on a black hole discovery, instead of rejecting one," says study lead Tomer Shenar, a Marie-Curie Fellow at Amsterdam University in the Netherlands.
The team includes Kareem El-Badry-nicknamed by fellow astronomers as the "black hole destroyer"-of the Center for Astrophysics | Harvard & Smithsonian (CfA). CalçadaĪ team of international experts who are known for debunking black hole discoveries have found a dormant stellar-mass black hole in the Large Magellanic Cloud, a galaxy that neighbors the Milky Way. The inclination of the system means that, when looking at it from Earth, we cannot observe the black hole eclipsing the star. Note that the 'lensing' effect around the black hole is shown for illustration purposes only, to make this dark object more noticeable in the image. The sizes of the two binary components are not to scale: in reality, the blue star is about 200 000 times larger than the black hole. The system, which is located in the Tarantula Nebula in the Large Magellanic Cloud, is composed of a hot, blue star with 25 times the Sun’s mass and a black hole, which is at least nine times the mass of the Sun. This artist’s impression shows what the binary system VFTS 243 might look like if we were observing it up close.