Supercomputer simulations reveals the nature of turbulence in black hole accretion disks
Black holes are by their very nature, challenging to observe and difficult to spot. It’s usually observations of the accretion disk that reveal properties of the hidden black hole. There is often enough material within the accretion disk to make them shine so brightly that they can often be among the brightest objects in space. A wonderful image has been released which shows the highest resolution simulation of a black hole accretion disk ever created.
This image is from a black hole simulator. It shows a supermassive black hole, or quasar, surrounded by a swirling disk of material called an accretion disk. There are many unanswered questions about black holes and how they grow to be so massive. Simulations is one way of finding answers. Image Credit: Caltech/Phil Hopkins group
In the beginning, the Universe was all primordial gas. Somehow, some of it was swept up into supermassive black holes (SMBHs), the gargantuan singularities that reside at the heart of galaxies. The details of how that happened and how SMBHs accumulate mass are some of astrophysics’ biggest questions.
A rocky planet with a large moon may have good potential to host life, given that the Moon controls essential aspects for life on Earth, including the length of the day, ocean tides, and stable climate. Image Credit: University of Rochester photo illustration by Michael Osadciw featuring Unsplash photography from Brad Fickeisen, Jaanus Jagomagi, and Engin Akyurt
There’s no perfect way of doing anything, including searching for exoplanets. Every planet-hunting method has some type of bias. We’ve found most exoplanets using the transit method, which is biased toward larger planets. Larger planets closer to their stars block more light, meaning we detect large planets transiting in front of their stars more readily than we detect small ones.
That’s a problem because some research says that life-supporting planets are more likely to be small, like Earth. It’s all because of moons and streaming instability.
Illustration of an active quasar. New research shows that SMBHs eat rapidly enough to trigger them. Credit: ESO/M. Kornmesser
At the heart of large galaxies like our Milky Way, there resides a supermassive black hole (SMBH.) These behemoths draw stars, gas, and dust toward them with their irresistible gravitational pull. When they consume this material, there’s a bright flare of energy, the brightest of which are quasars.
While astrophysicists think that SMBHs eat too slowly to cause a particular type of quasar, new research suggests otherwise.
How astronomers can measure the width of an accretion disk. Credit: NOIRLab/NSF/AURA/P. Marenfeld
When you think of a black hole, you might think its defining feature is its event horizon. That point of no return not even light can escape. While it’s true that all black holes have an event horizon, a more critical feature is the disk of hot gas and dust circling it, known as the accretion disk. And a team of astronomers have made the first direct measure of one.
The Drake Equation, a mathematical formula for the probability of finding life or advanced civilizations in the universe. Credit: University of Rochester
Did humanity miss the party? Are SETI, the Drake Equation, and the Fermi Paradox all just artifacts of our ignorance about Advanced Life in the Universe? And if we are wrong, how would we know?
A new study focusing on black holes and their powerful effect on star formation suggests that we, as advanced life, might be relics from a bygone age in the Universe.
Artist’s impression of a cataclysmic variable system as seen from the surface of an orbiting planet
Credit
Departamento de Imagen y Difusion FIME-UANL/ Lic. Debahni Selene Lopez Morales D.R. 2022
Licence type
Attribution-NonCommercial-NoDerivs (CC BY-NC-ND 4.0)
Have you heard of LU Camelopardalis, QZ Serpentis, V1007 Herculis and BK Lyncis? No, they’re not members of a boy band in ancient Rome. They’re Cataclysmic Variables, binary stars that are so close together one star draws material from its sibling. This causes the pair to vary wildly in brightness.
Can planets exist in this chaotic environment? Can we spot them? A new study answers yes to both.
Scientists have captured an intruder object disrupting the protoplanetary disk—birthplace of planets—in Z Canis Majors (Z CMa), a star in the Canis Majoris constellation. This artist’s impression shows the perturber leaving the star system, pulling a long stream of gas from the protoplanetary disk along with it. Observational data from the Subaru Telescope, Karl G. Jansky Very Large Array, and Atacama Large Millimeter/submillimeter Array suggest the intruder object was responsible for the creation of these gaseous streams, and its “visit” may have other as yet unknown impacts on the growth and development of planets in the star system.
Credit: ALMA (ESO/NAOJ/NRAO), B. Saxton (NRAO/AUI/NSF)
When it comes to observing protoplanetary disks, the Atacama Large Millimetre/sub-millimetre Array (ALMA) is probably the champion. ALMA was the first telescope to peer inside the almost inscrutable protoplanetary disks surrounding young stars and watch planets forming. ALMA advanced our understanding of the planet-forming process, though our knowledge of the entire process is still in its infancy.
According to new observations, it looks like chaos and disorder are part of the process. Astronomers using ALMA have watched as a star got too close to one of these planet-forming disks, tearing a chunk away and distorting the disk’s shape.
Researchers at WSU have created a fluid with a negative effective mass for the first time, which could open the door to studying the deeper mysteries of the Universe. Credit: ESA/Hubble, ESO, M. Kornmesse
Black holes are one of the most awesome and mysterious forces in the Universe. Originally predicted by Einstein’s Theory of General Relativity, these points in spacetime are formed when massive stars undergo gravitational collapse at the end of their lives. Despite decades of study and observation, there is still much we don’t know about this phenomenon.
For example, scientists are still largely in the dark about how the matter that falls into orbit around a black hole and is gradually fed onto it (accretion disks) behave. Thanks to a recent study, where an international team of researchers conducted the most detailed simulations of a black hole to date, a number of theoretical predictions regarding accretion disks have finally been validated.
A 5000 light year long jet observable in optical light from the giant elliptical galaxy M87 - which is not technically a blazar, but only because it's jet isn't more closely aligned with Earth. Credit: ESA/Hubble.
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Polar jets are often found around objects with spinning accretion disks – anything from newly forming stars to ageing neutron stars. And some of the most powerful polar jets arise from accretion disks around black holes, be they of stellar or supermassive size. In the latter case, jets emerging from active galaxies such as quasars, with their jets roughly orientated towards Earth, are called blazars.
The physics underlying the production of polar jets at any scale is not completely understood. It is likely that twisting magnetic lines of force, generated within a spinning accretion disk, channel plasma from the compressed centre of the accretion disk into the narrow jets we observe. But exactly what energy transfer process gives the jet material the escape velocity required to be thrown clear is still subject to debate.
In the extreme cases of black hole accretion disks, jet material acquires escape velocities close to the speed of light – which is needed if the material is to escape from the vicinity of a black hole. Polar jets thrown out at such speeds are usually called relativistic jets.
Relativistic jets from blazars broadcast energetically across the electromagnetic spectrum – where ground based radio telescopes can pick up their low frequency radiation, while space-based telescopes, like Fermi or Chandra, can pick up high frequency radiation. As you can see from the lead image of this story, Hubble can pick up optical light from one of M87‘s jets – although ground-based optical observations of a ‘curious straight ray’ from M87 were recorded as early as 1918.
Polar jets are thought to be shaped (collimated) by twisting magnetic lines of force. The driving force that pushes the jets out may be magnetic and/or intense radiation pressure, but no-one is really sure at this stage. Credit: NASA.
A recent review of high resolution data obtained from Very Long Baseline Interferometry (VLBI) – involving integrating data inputs from geographically distant radio telescope dishes into a giant virtual telescope array – is providing a bit more insight (although only a bit) into the structure and dynamics of jets from active galaxies.
The radiation from such jets is largely non-thermal (i.e. not a direct result of the temperature of the jet material). Radio emission probably results from synchrotron effects – where electrons spun rapidly within a magnetic field emit radiation across the whole electromagnetic spectrum, but generally with a peak in radio wavelengths. The inverse Compton effect, where a photon collision with a rapidly moving particle imparts more energy and hence a higher frequency to that photon, may also contribute to the higher frequency radiation.
Anyhow, VLBI observations suggest that blazar jets form within a distance of between 10 or 100 times the radius of the supermassive black hole – and whatever forces work to accelerate them to relativistic velocities may only operate over the distance of 1000 times that radius. The jets may then beam out over light year distances, as a result of that initial momentum push.
Shock fronts can be found near the base of the jets, which may represent points at which magnetically driven flow (Poynting flux) fades to kinetic mass flow – although magnetohydrodynamic forces continue operating to keep the jet collimated (i.e. contained within a narrow beam) over light year distances.
Left: A Xray/radio/optical composite photo of Centaurus A - also not technically a blazar because its jets don't align with the Earth. Credit: X-ray: NASA/CXC/CfA/R.Kraft et al.; Submillimeter: MPIfR/ESO/APEX/A.Weiss et al.; Optical: ESO/WFI. Right: A composite image showing the radio glow from Centaurus A compared with that of the full Moon. The foreground antennas are CSIRO's Australia Telescope Compact Array, which gathered the data for this image.
That was about as much as I managed to glean from this interesting, though at times jargon-dense, paper.
