See 2 black holes in cosmic dance

NASA has released a cool new visualization showing two massive black holes orbiting each other in a stunning display of light. The intense gravity and other phenomena all play a part in producing this mesmerizing display. Black holes are one of the most fascinating and mind-bending phenomena in the universe. The gravity of a black hole is so powerful that not even light can escape it. There are many varieties of black holes, and, in April 2021, NASA released a new visualization of binary (double) black holes, two black holes orbiting a common center of gravity, circling each other in a cosmic dance. The black holes depicted in this visualization are millions of times more massive than our sun. Each is surrounded by a disk of hot gas called an accretion disk. In the visualization, the gravity of the black holes distorts the light coming from their respective disks, producing a mesmerizing light show. Various other relativistic phenomena also contribute to the display.

Visualization of two massive black holes orbiting each other. The one in the foreground (with a red accretion disk) has a mass two hundred million times that of the sun, and its gravity bends the light coming from the accretion disk surrounding the smaller black hole (blue) behind it. The colors correspond to temperature, where the blue accretion disk is hotter and the red one is cooler. Image via NASA/ Goddard Space Flight Center/ Jeremy Schnittman/ Brian P. Powell.

Face-on overhead view of the two black holes and their accretion disks. A small and distorted edge-on view of the larger black hole appears near the smaller black hole, and a similar small image of the smaller black hole appears near the inner ring of light of the larger black hole. In effect, we are seeing both black holes from the side and from above at the same time. Image via NASA/ Goddard Space Flight Center/ Jeremy Schnittman/ Brian P. Powell.

How does this happen?

When you view the disks almost edge-on, from the orbital plane, they have a double-bulged look to them, reminiscent of seeing Saturn from the edge, slightly above or below the ring plane; a flat circular disk with a huge round bulge on top and bottom.

When one of the black holes passes in front of the other, however, as seen from our vantage point, the intense gravity of the black hole closer to us distorts the light coming from the black hole behind it. This creates a rapidly changing series of colorful arcs as they move. The light from both black holes is being modified by the distorted fabric of space-time near the black holes.

In the visualization, the light from the disks is shown as brilliant blue or red. This is partly to make them easier to distinguish, but also depicts the different temperatures of each disk. Hotter gas is shown as blue and cooler gas as red. Most of the light in both disks is emitted in the ultraviolet (UV) part of the electromagnetic spectrum instead of in visible light.

Stronger gravitational effects also produce higher temperatures so the disks look brighter on one side (the side closest to their respective holes). This is due to gravity distorting the light coming from different parts of the disks. The Doppler boosting effect – also known as relativistic beaming – also plays a part in these changes in brightness: the luminosity of the disk is affected by the gas moving faster near the black hole so that the side that is rotating toward the viewer appears brighter, while the side rotating away looks dimmer.

Another phenomenon that contributes to this visualization is relativistic aberration, where the black holes look smaller when they are moving closer to the viewer, but larger when moving away. That sounds counter-intuitive, but nature can be weird.

What happens if you look at the black holes from above, instead of from the side?

Those odd visual effects go away, but bizarre new ones take their place. Each black hole produces a small visual “copy” of the other black hole that orbits around it, sort of like watching a planet orbit a star from directly above. But those small copied images show the partner black hole in an edge-on view (the way we saw them before, from the side) instead of an above view. How does that happen? The light from the black hole disks is being bent by gravity at 90 degrees. This means that we can see both the primary black hole disk face-on from above, and the smaller image of the companion black hole disk edge-on, at the same time. How bizarre is that? Schnittman said:

A striking aspect of this new visualization is the self-similar nature of the images produced by gravitational lensing. Zooming into each black hole reveals multiple, increasingly distorted images of its partner.

The researchers used the Discover supercomputer at the NASA Center for Climate Simulation to create the visualization. It would have taken about a decade to make using just a regular desktop computer, but with Discover, while using only 2 percent of its 129,000 core processors, it took only a day.

The result is the beautiful movie of two black holes in their cosmic dance that you see here.

Black hole dubbed 'the Unicorn' may be galaxy's smallest one

Scientists have discovered what may be the smallest-known black hole in the Milky Way galaxy and the closest to our solar system - an object so curious that they nicknamed it 'the Unicorn.' The researchers said the black hole is roughly three times the mass of our sun, testing the lower limits of size for these extraordinarily dense objects that possess gravitational pulls so strong not even light can escape. A luminous star called a red giant orbits with the black hole in a so-called binary star system named V723 Mon.The black hole is located about 1,500 light years - the distance light travels in a year, 5.9 trillion miles (9.5 trillion km) - from Earth. While it may be the closest one to us, it is still far away. By way of comparison, the closest star to our solar system, Proxima Centauri, is 4 light years away. Black holes like this one form when massive stars die and their cores collapse. "We nicknamed this black hole 'the Unicorn' partly because V723 Mon is in the Monoceros constellation - which translates to unicorn - and partly because it is a very unique system" in terms of the black hole's mass and relative closeness to Earth, said Ohio State University astronomy doctoral student Tharindu Jayasinghe, lead author of the study published this week in the journal Monthly Notices of the Royal Astronomical Society.

There are three categories of black holes. The smallest, like 'the Unicorn,' are so-called stellar mass black holes formed by the gravitational collapse of a single star. There are gargantuan 'supermassive' black holes like the one at our galaxy's center, 26,000 light years from Earth, which is four million times the sun's mass. A few intermediate-mass black holes also have been found with masses somewhere in between.

"It is clear that nature makes black holes of a wide range of masses. But a three-solar-mass black hole is a big surprise. There are no very good models for how to make such a black hole, but I am sure people will work on that more now," said Ohio State University astronomy professor and study co-author Kris Stanek.

'The Unicorn' falls into what the researchers called a "mass gap" between the largest-known neutron stars - objects similarly formed by a large star's collapse - at around 2.2 times the mass of our sun and what previously had been considered the smallest black holes at around five times the sun's mass.

"'The 'unicorn' is truly one of the smallest black holes possible," Jayasinghe said.

Its strong gravity alters the shape of its companion star in a phenomenon known as tidal distortion, making it elongated rather than spherical and causing its light to change as it moves along its orbital path. It was these effects on the companion star, observed using Earth-based and orbiting telescopes, that indicated the black hole's presence.

"Black holes are electromagnetically dark, and so they are difficult to find," Jayasinghe said.

Unlike some other black holes orbiting with a star, this one was not observed to be drawing material from its companion, which is 173 times more luminous than our sun.

The only smaller potential black hole is one with a mass 2.6 times that of our sun that was spotted in another galaxy, Jayasinghe said.

Обнаружено загадочное поведение гигантских черных дыр

Ученые Университета Претории в ЮАР провели детальные наблюдения за активными ядрами галактик, где находятся гигантские черные дыры, и обнаружили, что между ними имеется необъяснимая пока разница. Некоторые галактики молчат в радиодиапазоне, хотя их черные дыры активно пожирают материю. Кроме того, специалисты обнаружили и другие различия. Выводы исследователей опубликованы в репозитории препринтов arXiv, кратко о них рассказывается в статье на Science Alert. Астрономы провели анализ результатов наблюдений области космоса, известной как GOODS-North и расположенной в созвездии Большая Медведица. Данные были получены благодаря глубокому обзору GOODS (The Great Observatories Origins Deep Survey) с помощью космического телескопа Хаббл, телескопа Спитцер, рентгеновской обсерватории Chandra, а также других инструментов. Ученым удалось идентифицировать активные галактические ядра, содержащие сверхмассивные черные дыры. Ученые заметили разницу между аккрециями (процессами поглощения материала) у разных сверхмассивных черных дыр: некоторые притягивали к себе вещество намного быстрее, чем другие, а некоторые не поглощали материю вовсе. При этом скорость аккреции не играет особой роли на образование релятивистских джетов — струй ионизированной плазмы, вырывающихся с полюсов черной дыры со скоростью, составляющей значительный процент от скорости света. Некоторые черные дыры не испускают радиоизлучения, что указывает на существование пока еще не известного механизма, играющего роль в формировании джетов.

Астрономы также оценили связь между активными черными дырами и звездообразованием в галактиках. Считается, что активное ядро подавляет процесс возникновения новых звезд, поскольку «сдувает» межзвездное вещество из галактики. В некоторых случаях может произойти и обратное: ударные волны могут способствовать коллапсу материи в звезды. Ученые показали, что в некоторых галактиках действительно наблюдается звездообразование.

Результаты наблюдений помогут лучше понять эволюцию галактик, а также процессов поглощения и поведения сверхмассивных черных дыр, чье происхождение пока остается загадкой.

Piercing Through a Galaxy’s Dusty Core to Uncover the Secrets of an Active Supermassive Black Hole

 As technology has improved over the centuries, so have astronomers’ observations of nearby galaxy Centaurus A. They have peeled back its layers like an onion to discover that its wobbly shape is the result of two galaxies that merged more than 100 million years ago. It also has an active supermassive black hole, known as an active galactic nucleus, at its heart that periodically sends out twin jets. Despite these advancements, Centaurus A’s dusty core is still quite mysterious. Webb’s high-resolution infrared data will allow a research team to very precisely reveal all that lies at the center. Centaurus A is a giant of a galaxy, but its appearances in telescope observations can be deceiving. Dark dust lanes and young blue star clusters, which crisscross its central region, are apparent in ultraviolet, visible, and near-infrared light, painting a fairly subdued landscape. But by switching to X-ray and radio light views, a far more raucous scene begins to unfold: From the core of the misshapen elliptical galaxy, spectacular jets of material have erupted from its active supermassive black hole – known as an active galactic nucleus – sending material into space well beyond the galaxy’s limits. What, precisely, is happening at its core to cause all this activity? Upcoming observations led by Nora Lützgendorf and Macarena García Marín of the European Space Agency using NASA’s James Webb Space Telescope will allow researchers to peer through its dusty core in high resolution for the first time to begin to answer these questions.

Centaurus A’s dusty core is apparent in visible light, but its jets are best viewed in X-ray and radio light. With upcoming observations from NASA’s James Webb Space Telescope in infrared light, researchers hope to better pinpoint the mass of the galaxy’s central supermassive black hole as well as evidence that shows where the jets were ejected. Credit: X-ray: NASA/CXC/SAO; optical: Rolf Olsen; infrared: NASA/JPL-Caltech; radio: NRAO/AUI/NSF/Univ.Hertfordshire/M.Hardcastle

“There’s so much going on in Centaurus A,” explains Lützgendorf. “The galaxy’s gas, disk, and stars all move under the influence of its central supermassive black hole. Since the galaxy is so close to us, we’ll be able to use Webb to create two-dimensional maps to see how the gas and stars move in its central region, how they are influenced by the jets from its active galactic nucleus, and ultimately better characterize the mass of its black hole.”

A Quick Look Back

Let’s hit “rewind” to review a bit of what is already known about Centaurus A. It’s well studied because it’s relatively nearby – about 13 million light-years away – which means we can clearly resolve the full galaxy. The first record of it was logged in the mid-1800s, but astronomers lost interest until the 1950s because the galaxy appeared to be a quiet, if misshapen, elliptical galaxy. Once researchers were able to begin observing with radio telescopes in the 1940s and ’50s, Centaurus A became radically more interesting – and its jets came into view. In 1954, researchers found that Centaurus A is the result of two galaxies that merged, which was later estimated to have occurred 100 million years ago.

Supermassive black holes, which lie at the centers of galaxies, are voracious. They periodically “sip” or “gulp” from the swirling disks of gas and dust that orbit them, which can result in massive outflows that affect star formation locally and farther afield. When NASA’s James Webb Space Telescope begins observing galaxies’ cores, its infrared instruments will pierce through the dust to deliver images and incredibly high-resolution data that allow researchers to learn precisely how one process sets off another, and how they create an enormous feedback loop. Credit: NASA, ESA, and L. Hustak (STScI)

With more observations in the early 2000s, researchers estimated that about 10 million years ago, its active galactic nucleus shot out twin jets in opposite directions. When examined across the electromagnetic spectrum, from X-ray to radio light, it’s clear there is far more to this story that we still have to learn.

“Multi-wavelength studies of any galaxy are like the layers of an onion. Each wavelength shows you something different,” said Marín. “With Webb’s near- and mid-infrared instruments, we’ll see far colder gas and dust than in previous observations, and learn much more about the environment at the center of the galaxy.”

Visualizing Webb’s Data

The team led by Lützgendorf and Marín will observe Centaurus A not only by taking images with Webb, but by gathering data known as spectra, which spread out light into its component wavelengths like a rainbow. Webb’s spectra will reveal high-resolution information about the temperatures, speeds, and compositions of the material at the center of the galaxy.

In particular, Webb’s Near Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI) will provide the research team with a combination of data: an image plus a spectrum from within each pixel of that image. This will allow the researchers to build intricate 2D maps from the spectra that will help them identify what’s happening behind the veil of dust at the center – and analyze it from many angles in depth.

Compare this style of modeling to the analysis of a garden. In the same way botanists classify plants based on specific sets of features, these researchers will classify spectra from Webb’s MIRI to construct “gardens” or models. “If you take a snapshot of a garden from a great distance away,” Marín explained, “You will see something green, but with Webb, we will be able to see individual leaves and flowers, their stems, and maybe the soil underneath.”

As the research team digs into the spectra, they’ll build maps from individual parts of the garden, comparing one spectrum to another nearby spectrum. This is analogous to determining which parts contain which plant species based on comparisons of “stems,” “leaves,” and “flowers” as they go.

“When it comes to spectral analysis, we conduct many comparisons,” Marín continued. “If I compare two spectra in this region, maybe I will find that what was observed contains a prominent population of young stars. Or confirm which areas are both dusty and heated. Or maybe we will identify emission coming from the active galactic nucleus.”

In other words, the “ecosystem” of spectra has many levels, which will allow the team to better define precisely what is present and where it is – which is made possible by Webb’s specialized infrared instruments. And, since these studies will build on many that came before, the researchers will be able to confirm, refine, or break new ground by identifying new features.

Weighing the Black Hole in Centaurus A

The combination of images and spectra provided by NIRSpec and MIRI will allow the team to create very high-resolution maps of the speeds of the gas and stars at the center of Centaurus A. “We plan to use these maps to model how the entire disk at the center of the galaxy moves to more precisely determine the black hole’s mass,” Lützgendorf explains.

Watch as the jets and winds from a supermassive black hole affect its host galaxy—and the space hundreds of thousands of light-years away over millions of years. Credit: NASA, ESA, and L. Hustak (STScI)

Since researchers understand how the gravity of a black hole governs the rotation of nearby gas, they can use the Webb data to weigh the black hole in Centaurus A. With a more complete set of infrared data, they will also determine if different parts of the gas are all behaving as anticipated. “I’m looking forward to fully filling out our data,” Lützgendorf said. “I hope to see how the ionized gas behaves and twirls, and where we see the jets.”

The researchers are also hoping to break new ground. “It’s possible we’ll find things we haven’t considered yet,” Lützgendorf explains. “In some aspects, we’ll be covering completely new territory with Webb.” Marín wholeheartedly agrees, and adds that building on a wealth of existing data is invaluable. “The most exciting aspects about these observations is the potential for new discoveries,” she said. “I think we might find something that makes us look back to other data and reinterpret what was seen earlier.”

These studies of Centaurus A will be conducted as part of Gillian Wright and Pierre Ferruit’s joint MIRI and NIRSpec Guaranteed Time Observations programs. All of Webb’s data will ultimately be stored in the publicly accessible Barbara A. Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute in Baltimore.

The James Webb Space Telescope will be the world’s premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.