Our study helps us understand how gas is expelled or captured by galaxies in the young Universe and how black holes grow and can impact the evolution of galaxies. We know that the fate of galaxies such as the Milky Way is closely linked to that of black holes, since these can generate galactic storms capable of extinguishing the formation of new stars. Studying the primordial eras allows us to understand the initial conditions of the Universe we see today. - Manuela Bischetti
For the first time, our group has come together to discuss the discovery of a black hole, instead of eliminating one.We are talking about a black hole found inside the Tarantula Nebula, which is part of the Large Magellanic Cloud, one of the satellite galaxies of the Milky Way.
[It] appears to have completely collapsed, with no sign of a previous explosion.This black hole, the first extragalactic, was discovered orbiting a massive star thanks to six years of observations at ESO's Very Large Telescope.
With the help of ESO’s Very Large Telescope (VLT), astronomers have found six galaxies lying around a supermassive black hole when the Universe was less than a billion years old. This is the first time such a close grouping has been seen so soon after the Big Bang and the finding helps us better understand how supermassive black holes, one of which exists at the centre of our Milky Way, formed and grew to their enormous sizes so quickly. It supports the theory that black holes can grow rapidly within large, web-like structures which contain plenty of gas to fuel them.The location of the supermassive black hole is in the Sextans' constellation.
Planet Nine has been proposed to potentially be a black hole in the outer solar system. We investigate the accretion flares that would result from impacts of small Oort cloud objects, and find that the upcoming LSST observing program will be able to either rule out or confirm Planet Nine as a black hole within a year. We also find that LSST could rule out or confirm the existence of trapped planet-mass black holes out to the edge of the Oort cloud, indirectly probing the dark matter fraction in subsolar mass black holes and potentially improving upon current limits by orders of magnitude.
This graphic shows the computer simulation of a black hole from start to finish. Plasma is falling slowly toward the black hole in a (at the upper left). The plasma has a magnetic field, shown by the white lines. It picks up speed as it falls toward the hole in b (at the upper right), c (lower left) and d (lower right). However, the rotating black hole twists up space itself (and the magnetic field lines) and ejects electromagnetic power along the north and south poles above the black hole. The red and white color shows the immense electromagnetic power output, which eventually will pick up particles and form squirting jets. This simulation was conducted using supercomputers at Japan's National Institute for Fusion Science.source: archive.org
Using eight sensitive radio telescopes strategically positioned around the world in Antarctica, Chile, Mexico, Hawaii, Arizona and Spain, a global collaboration of scientists at 60 institutions operating in 20 countries and regions captured an image of a black hole for the first time. By synchronizing each telescope using a network of atomic clocks, the team created a virtual telescope as large as the Earth, with a resolving power never before achieved from the surface of our planet. One of their first targets was the supermassive black hole at the center of the Messier 87 galaxy – its mass equivalent to 6.5 billion suns. After painstakingly analyzing the data with novel algorithms and techniques, the team produced an image of this galactic monster, silhouetted against hot gas swirling around the black hole, that matched expectations from Einstein's theory of gravity: a bright ring marking the point where light orbits the black hole, surrounding a dark region where light cannot escape the black hole's gravitational pull.2020 Breakthrough Prize in Mathematics to Alex Eskin, for revolutionary discoveries in the dynamics and geometry of moduli spaces of Abelian differentials, including the proof of the "magic wand theorem" with Maryam Mirzakhani.
Eskin teamed with famed Iranian mathematician and Fields Medalist, Maryam Mirzakhni, to prove a theorem about dynamics on moduli spaces. Their tour de force, published in 2013 after five years of labor, is a result with many consequences. One addresses the longstanding problem: If a beam of light from a point source bounces around a mirrored room, will it eventually reach the entire room – or will some parts remain forever dark? After translating the problem to a highly abstract multi-dimensional setting, the two mathematicians were able to show that for polygonal rooms with angles which are fractions of whole numbers, only a finite number of points would remain unlit. Mirzakhani passed away in 2017, at age 40, after fighting breast cancer for several years.
On January 4th, 2017, LIGO detected two black holes merging into one. One of the black holes was 32 times the mass of the Sun, while the other was 19 times the mass of the Sun. When they merged, they created a black hole 49 times the mass of the Sun. The coalescence instantly converted 2 solar masses of black hole mass into the energy that rattled spacetime enough to generate the gravitational waves we detected almost 3 billion years after it occurred. (Caltech/MIT/LIGO Lab)Read also: LIGO Picks Up on the Third Ring
The 3d volume inside a spherical black hole can be defined by extending an intrinsic flat-spacetime characterization of the volume inside a 2-sphere. For a collapsed object, the volume grows with time since the collapse, reaching a simple asymptotic form, which has a compelling geometrical interpretation. Perhaps surprising, it is large. The result may have relevance for the discussion on the information paradox.
A sphere $S$ on the event horizon bounds a spacelike hypersurface, a large portion of which coincides with an $r$ = constant hypersurface. We show this hypersurface with one dimension suppressed, and cut in the middle, omitting the long cylindrical part which gives the main contribution to its volume. We also illustrate the argument showing that most of the volume is contained in a region out of causal contact with matter that has advanced far into the black hole.
In this paper we present a new scenario where massive Primordial Black Holes (PBH) are produced from the collapse of large curvature perturbations generated during a mild waterfall phase of hybrid inflation. We determine the values of the inflaton potential parameters leading to a PBH mass spectrum peaking on planetary-like masses at matter-radiation equality and producing abundances comparable to those of Dark Matter today, while the matter power spectrum on scales probed by CMB anisotropies agrees with Planck data. These PBH could have acquired large stellar masses today, via merging, and the model passes both the constraints from CMB distortions and micro-lensing. This scenario is supported by Chandra observations of numerous BH candidates in the central region of Andromeda. Moreover, the tail of the PBH mass distribution could be responsible for the seeds of supermassive black holes at the center of galaxies, as well as for ultra-luminous X-rays sources. We find that our effective hybrid potential can originate e.g. from D-term inflation with a Fayet-Iliopoulos term of the order of the Planck scale but sub-planckian values of the inflaton field. Finally, we discuss the implications of quantum diffusion at the instability point of the potential, able to generate a swiss-cheese like structure of the Universe, eventually leading to apparent accelerated cosmic expansion.
The Penrose process is a process theorised by Roger Penrose wherein energy can be extracted from a rotating black hole. That extraction is made possible because the rotational energy of the black hole is located, not inside the event horizon of the black hole, but on the outside of it in a region of the Kerr spacetime called the ergosphere, a region in which a particle is necessarily propelled in locomotive concurrence with the rotating spacetime. All objects in the ergosphere become dragged by a rotating spacetime. In the process, a lump of matter enters into the ergosphere of the black hole, and once it enters the ergosphere, it is split into two. The momentum of the two pieces of matter can be arranged so that one piece escapes to infinity, whilst the other falls past the outer event horizon into the hole. The escaping piece of matter can possibly have greater mass-energy than the original infalling piece of matter, whereas the infalling piece has negative mass-energy. In summary, the process results in a decrease in the angular momentum of the black hole, and that reduction corresponds to a transference of energy whereby the momentum lost is converted to energy extracted.
The process obeys the laws of black hole mechanics. A consequence of these laws is that if the process is performed repeatedly, the black hole can eventually lose all of its angular momentum, becoming non-rotating, i.e. a Schwarzschild black hole. Demetrios Christodoulou calculated an upper bound for the amount of energy that can be extracted by the Penrose process.
Over the past three decays, since the discovery of quasars, mounting observational evidence has accumulated that black holes indeed exist in nature. In this paper, I present a theoretical and numerical (Monte Carlo) fully relativistic 4-D analysis of Penrose scattering processes (Compton and $\gamma \gamma \rightarrow e^+ e^-$) in the ergosphere of a supermassive Kerr (rotating) black hole. These model calculations surprisingly reveal that the observed high energies and luminosities of quasars and other AGNs, the collimated jets about the polar axis, and the asymmetrical jets (which can be enhanced by relativistic Doppler beaming effects), all, are inherent properties of rotating black holes. That is, from this analysis, it is shown that the Penrose scattered escaping particles exhibit tightly wounded coil-like cone distributions (highly collimated jet distributions) about the polar axis, with helical polar angles of escape varying from 0.5o to 30o for the highest energy particles. It is also shown that the gravitomagnetic (GM) field, which causes the dragging of inertial frames, exerts a force acting on the momentum vectors of the incident and scattered particles, causing the particle emission to be asymmetrical above and below the equatorial plane, thus breaking the reflection symmetry of the Kerr metric (above and below the equatorial plane). When the accretion disk is assumed to be a two-temperature bistable thin disk/ion corona, recently referred to as an advection dominated accretion flow (ADAF), energies as high as 54 GeV can be attained by these Penrose processes alone; and when relativistic beaming is included, energies in the TeV range can be achieved, agreeing with observations of some BL Lac objects. When this model is applied specifically to quasars 3C 279 and 3C 273, their observed high energy luminosity spectra can be duplicated and explained. Moreover, this Penrose energy extraction model can be applied to any size black hole, irrespective of the mass, and, thus, suggests a complete theory for the extraction of energy from a black hole.
Sagittarius A* (pronounced "Sagittarius A-star", standard abbreviation Sgr A*) is a bright and very compact astronomical radio source at the center of the Milky Way Galaxy, near the border of the constellations Sagittarius and Scorpius. It is part of a larger astronomical feature known as Sagittarius A. Sagittarius A* is believed to be the location of a supermassive black hole,(1, 2) like those that are now generally accepted to be at the centers of most spiral and elliptical galaxies. Observations of the star S2 in orbit around Sagittarius A* have been used to show the presence of, and produce data about, the Milky Way's central supermassive black hole, and have led to the conclusion that Sagittarius A* is the site of that black hole(3).
the x-ray emission from Sgr A* can be described as the superposition of a pointlike source from the black hole itself, and a much larger extended cloud of emission about 2″ across. Within this cloud, we can identify over a hundred individually resolved bright stars, and infer thousands more that are too dim to detect.(5)They also infer that
the temperature and density profile of the gas cloud surrounding Sgr A*. They show that over 99% of the gas never reaches the central black hole, but rather is ejected from the system(5)There are also some unresolved questions: for example if the observed accretion rate is dued exclusively by Sgr A* or if there is another source for the data; or his low luminosity, orders of magnitude below its theoretical potential(5).
