Stephen Hawking, James Hartle and Alexei Starobinski are no longer with us, nor is John Wheeler, but other great pioneers of black hole theory are! Like Roger Penrose and Kip Thorne. It is often said that it was the work of Robert Oppenheimer that laid the foundation for the theory of black holes, but we can draw on the work of Subrahmanyan Chandrasekhar, who was the first to realize that a star is exhausted above a certain mass Its thermonuclear fuel is forced to collapse by gravity, resulting in what we now call a black hole.
Today, the fascination with these compact stars that distort time and space, which still hold many secrets and perhaps sometimes represent gateways to parallel universes, is fueled in particular by Interstellar and the image of the all-black star M87* revealed through the collaboration with the event Horizon Telescope. Many people therefore undoubtedly want to take part in one of the greatest adventures of the noosphere of the geochemist Vladimir Vernadsky and the geologist and paleontologist Pierre Teilhard de Chardin, the collective mind of Homo sapiens, so to speak, and help discover the secrets of black holes. But they probably also think that this is a possibility reserved for astrophysicists.
But as Arthur Clarke predicted in a BBC broadcast in the 1960s, advances in telecommunications and computing have not only helped this noosphere develop a planetary consciousness and culture, but the rise of the Internet for more than 30 years It also allows anyone with a computer to help the scientific community make discoveries without having any scientific training. It has already been possible to help astrophysicists discover supermassive black holes in the hearts of large galaxies by connecting online with Radio Galaxy Zoo as part of the famous Zooniverse. This well-known citizen science portal is an extension of the original Galaxy Zoo project, which asked internet users to classify galaxies.
For some time now, anyone has been able to hunt stellar black holes in the Milky Way with another Zooniverse avatar: Black Hole Hunters.
Subrahmanyan Chandrasekhar and black holes. To get a reasonably accurate French translation, click on the white rectangle at the bottom right. English subtitles should then appear. Then click on the nut to the right of the rectangle, then click on “Subtitles” and finally “Auto-translate”. Select “French”. © OpenLearn by The Open University
Wandering or isolated stellar black holes
What is it about ?
We know that most stars in the Milky Way are binary stars, often with at least one massive star ending its short life in a supernova. If one of these stars is particularly massive, it is more likely to leave behind a black hole as a stellar corpse rather than a neutron star.
It could be that the resulting explosion disrupts the binary star system and results in a wandering stellar black hole. It is also possible that the orbits are altered or that the black hole, although still gravitationally connected to the other star on the famous main sequence, is too far away to rip off material from the companion star.
In this case, an accretion disk does not form around the black hole, in which coils of matter heat up to radiation in the X range, so to speak, because these coils rub against each other. on the other (we speak of viscous friction for the gas streams involved) by causing the matter to fall towards the event horizon of the black hole, that fictitious membrane under which, according to the general theory of relativity, any fallen matter is hopelessly trapped because of its speed of light would have to exceed in order to escape the bubble defined by the horizon.
A wandering black hole, or one without an accretion disk, seems destined to forever escape the eyes of the noosphere and all black hole hunters.
This animation illustrates the concept of gravitational microlensing with a black hole. When the black hole appears to pass almost in front of a background star, the light rays from the source star are diffracted due to the distorted space-time around the foreground black hole. This becomes a virtual magnifying glass, amplifying the brightness of the distant star in the background. Unlike a star or planet as a lensing object, black holes distort space-time so much that the apparent position of the distant star in the sky changes noticeably. © NASA
Passing black holes with gravitational microlensing
But that is not true.
Although the event is rarely surprising and the largest possible region of the sky must be monitored over a long period of time, it is quite possible for an observer to see a black hole of this type pass in front of a star. The black hole's strong gravitational field deflects the light rays like a lens.
The star undergoing a transit therefore temporarily becomes brighter, its light intensity curve then contains a peak and this peak is created by a so-called gravitational microlensing effect, which researchers Matt Middleton and Adam McMaster from the University of Southampton and their colleague Dr. Hugh Dickinson of the Open University (a public and open university in the United Kingdom founded in 1969) offers Internet users the ability to search in the light curves recorded in research campaigns originally intended to detect planetary transits.
Therefore, for a time, the Black Hole Hunters website offered to study the data from SuperWASP (Wide Angle Search for Planets), an exoplanet search project carried out from 2004 to 2016 using ground-based telescopes at the sites of two observatories: the Roque de los Muchachos Observatory and the South African Astronomical Observatory.
But today, data from the Transiting Exoplanet Survey Satellite (Tess), now a famous exoplanet hunter, can be used.
Despite advances in AI, it is still Homo Sapiens who can most effectively hunt microlensing effects in light curves. Even if this is still the case, do not hesitate to transform yourself into a black hole hunter by following the instructions that are easy to put into practice!