Tag Archives: Hole

NASA releases beautiful new animation of a black hole

A beautiful new animation produced by NASA helps visualize the relationship between gravity, time, and space.

Image credits NASA Goddard Space Flight Center / Jeremy Schnittman.

Researchers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have generated a new animation of a black hole and its surrounding matter disk. The animation is based on radio images of a black hole at the core of galaxy M87 taken by the Event Horizon Telescope.

Bendy time

“Simulations and movies like these really help us visualize what Einstein meant when he said that gravity warps the fabric of space and time,” says Jeremy Schnittman, Ph.D., the NASA astrophysicist who generated these gorgeous images using custom software

Schnittman’s work helps to showcase how the huge gravity around a black hole distorts the way we perceive its surroundings. That halo-like structure is, in fact, a disk. This accretion disk is a relatively thin mass of gas infalling into the black hole; we see it in the particular shape shown above because gravity is bending light around the black hole. It’s pretty similar to bending a picture of the disk.

Gas in accretion disks is very hot (through a combination of friction and compression), so it radiates in different parts of the electromagnetic spectrum. Those around the youngest of stars glow in infrared, but the disk in this animation glows with X-rays, because it has a lot of energy. It ripples and flows as magnetic fields move along its bulk. This creates brighter and dimmer bands in the disk.

The gas also moves faster the closer it gets to the black hole — close to the speed of light nearest to it. In the animation above, this makes the left side look brighter than the right side due to redshift.

The thin line of light that seemingly outlines the black hole is its “photon ring”. You’re actually looking at the underside of the disk, its image bent back to us by the massive gravitational pull there. What we see as the photon ring is made up of several layers that grow progressively thinner and dimmer — this is light that’s been bent several times around the black hole before escaping for our telescopes to capture. Schnittman’s model uses a spherical black hole, so here the photon ring looks identical from every angle.

“Until very recently, these visualizations were limited to our imagination and computer programs,” Schnittman says. “I never thought that it would be possible to see a real black hole.”

Clouds.

Climate change and ozone layer holes form feedback loop, reports international panel

The frays in our planet’s ozone layer are leading to changes in the planet’s climate and ecosystem, new research shows.

Clouds.

Image via Pixabay.

Increased solar radiation levels, a consequence of damage to the ozone layer, are causing shifts in the climate which impact the Earth’s natural systems. These changes affect everything from weather to the health and distribution of sea life according to the study’s authors, members of the United Nations Environment Programme’s Environmental Effects Assessment Panel, which informs parties to the Montreal Protocol.

No-ozone zone

“What we’re seeing is that ozone changes have shifted temperature and precipitation patterns in the southern hemisphere, and that’s altering where the algae in the ocean are, which is altering where the fish are, and where the walruses and seals are, so we’re seeing many changes in the food web,” said Kevin Rose, a researcher at Rensselaer Polytechnic Institute who serves on the panel and is a co-author of the review article.

The 1987 Montreal Protocol on Substances that Deplete the Ozone Layer, often shorthanded as the ‘Montreal Protocol’, was the first ever multilateral environmental agreement ratified by all members of the United Nations. Its aim was to protect Earth’s ozone layer (which acts like a kind of planetary sunscreen, blocking UV radiation) by phasing out harmful handmade substances, most notably the chlorofluorocarbons class of refrigerants. All in all, the Protocol was a success, and total mean ozone levels are on track to recover to pre-1980s levels by the middle of this century.

Earlier this year, however, researchers reported detecting new emissions of ozone-depleting substances from East Asia, which could throw a wrench into the plan.

The link between ozone depletion and an increase in UV levels on the Earth’s surface is well known and well documented. However, the effect it has on climate isn’t. In fact, we’ve only recently wisened up to the fact that climate is also affected by ozone depletion. The current paper focuses on the Southern Hemisphere, where a hole in the ozone layer is currently centered around Antarctica.

The increased levels of UV radiation passing through this area have pushed the Antarctic Oscillation — the north-south movement of a wind belt that circles the Southern Hemisphere — further south than it has been in roughly a thousand years, the team reports. This shift is directly fueling climatic changes in the Southern Hemisphere, they add.

In effect, the hole is causing climate zones to shift southward, affecting rainfall patterns, sea-surface temperatures, and ocean currents across large areas of the southern hemisphere. For example, some areas of the oceans have become cooler and more productive, while others have warmed up and lost productivity.

These changes domino into terrestrial and aquatic ecosystems from Australia, New Zealand, Antarctica, South America, Africa, and the Southern Ocean. Warmer oceans are linked to declines in Tasmanian kelp beds and Brazilian coral reefs, and the ecosystems that rely on them. Cooler areas have helped some populations of penguins, seabirds, and seals, who now have more krill and fish to feed on.

Rose also points out to feedback loops linking climate to UV radiation. Higher concentrations of atmospheric CO2, for example, have increased overall ocean acidity. Acid attacks calcium carbonate, the main component of shellfish shells, which renders these animals more vulnerable to UV radiation. Even us, he adds, are likely to wear lighter clothes in the warmer atmosphere we’re creating, making ourselves more susceptible to damaging UV rays. Furthermore, the team found evidence that climate change is also impacting the ozone layer and its recovery.

“Greenhouse gas emissions trap more heat in the lower atmosphere which leads to a cooling of the upper atmosphere. Those colder temperatures in the upper atmosphere are slowing the recovery of the ozone layer,” Rose said.

As one of three scientific panels to support the Montreal Protocol, the Environmental Effects Assessment Panel focused in particular on the effects of UV radiation, climate change, and ozone depletion. Thirty-nine researchers contributed to the article. Rose, an aquatic ecologist, collaborated with the aquatic ecosystems working group, which is one of seven working groups that are part of the panel.

The paper “Ozone depletion, ultraviolet radiation, climate change and prospects for a sustainable future” has been published in the journal Nature Sustainability.

Sagittarius A*

Researchers find black hole that spins almost as fast as (we think) they can spin

New research led by members from the University of Southampton has identified a black hole spinning around its axis near its maximum possible speed.

Sagittarius A*

A simulated image of supermassive black hole Sagittarius A*, showing against a background of radiation and bright matter swept into the event horizon. The image was generated with data recorded by the Event Horizon Telescope.
Image credits National Radio Astronomy Observatory,

The study involved an international team of astronomers. Starting from observations taken with state-of-the-art sensors, the researchers found evidence that 4U 1630-472, a stellar-mass black hole in our galaxy, is rotating really, really fast — around 92% to 95% of a black hole’s theoretical maximum rotational speed.

Material keeps falling into this black hole as its spinning, being subjected do immense gravitational stress and temperatures. The environment is so violent that this matter shines brightly in X-rays, the team reports, which they used to establish that 4U 1630-472 is rotating and calculate its speed.

So fast it’s glowing

If a black hole is rotating rapidly enough, it should — according to the general theory of relativity — distort space-time around it differently than a non-rotating black hole, the team explains. Such distortions would leave a measurable trace on the radiation emitted by the matter it’s absorbing.

Therefore, researchers can look at a black hole’s emission spectra to determine the rate it’s spinning at.

“Detecting signatures that allow us to measure spin is extremely difficult,” says lead author Dr. Mayukh Pahari from the University of Southampton. “The signature is embedded in the spectral information which is very specific to the rate at which matter falls into the black hole.”

“The spectra, however, are often very complex mostly due to the radiation from the environment around the black hole.”

Dr. Pahari says the team was “lucky” to obtain a spectral reading directly from the matter falling into the black hole, sans the background noise. Armed with that data, it was “simple enough to measure the distortion caused by the rotating black hole,” he says.

The findings from this study are significant, as this is one of only a handful of times we’ve managed to accurately measure a black hole’s spin rate. Only five other black holes have shown high spin rates, the team adds. Astronomical black holes can be fully characterized by mass and spin rate. Therefore, measuring these two properties is key to understanding some extreme aspects of the universe and the fundamental physics related to them.

The paper “AstroSat and Chandra View of the High Soft State of 4U 1630–47 (4U 1630–472): Evidence of the Disk Wind and a Rapidly Spinning Black Hole” has been published in The Astrophysical Journal.

Supermassive Black Hole.

Supermassive black holes like to wear gas donuts — and we found out why

Supermassive black holes don’t really form dust ‘donuts’ — the structures surrounding these bodies are more akin to galactic matter fountains, new research reveals.

Supermassive Black Hole.

Artist’s concept of a supermassive black hole. Also shown are the accretion disk (donut) and the outflowing jet of energetic particles.
Image credits NASA-JPL.

Computer simulations and new observations from the Atacama Large Millimeter/submillimeter Array (ALMA) suggest that the gas accretion rings around supermassive black holes (SBH) aren’t ring-shaped at all. Instead, gas being expelled from the SBM interacts with infalling matter to create a complex circulation pattern — one which the authors liken to a fountain.

Jets of matter

Most galaxies revolve around a SBH. These objects can be millions, even billions of times as heavy as the Sun, and they knit together galaxies through sheer gravitational power. Some of these SBHs are actively consuming new material. So far, common wisdom held that instead of falling directly in, matter builds around an active black hole in a donut or ring-shaped structure.

It wasn’t far from the truth but, new research reveals, it wasn’t spot-on either. A study led by Takuma Izumi, a researcher at the National Astronomical Observatory of Japan (NAOJ), reports that this ‘donut’ is not actually a rigid structure, rather a complex collection of highly dynamic gaseous components.

The researchers used the ALMA telescope to observe the Circinus Galaxy and the SBH at its center — which is roughly 14 million light-years away from Earth. They then compared their observations to computer models of gas falling toward a black hole. These simulations were run using the Cray XC30 ATERUI supercomputer operated by NAOJ.

All in all, the team found that there’s a surprising level of interplay between the gases in this structure. Cold molecular gas first falls towards the black hole to form a disk near the plane of rotation. Being so close to a black hole heats up the gas until its atoms break apart into protons and electrons. Not all of these products go on to be swallowed by the black hole. Some are instead expelled above and below the disk but are then snagged by the SBH’s immense gravitational presence, falling back onto the disk.

SBH interaction.

Rough schematic of the process’ dynamics. Pc stands for parsec, equal to about 3.26 light-years (30 trillion km or 19 trillion miles).

These three components circulate continuously, the team explains. Their interaction creates three-dimensional flows of highly turbulent matter around the black hole.

“Previous theoretical models set a priori assumptions of rigid donuts,” explains co-author Keiichi Wada, a theoretician at Kagoshima University in Japan who lead the simulation study.

“Rather than starting from assumptions, our simulation started from the physical equations and showed for the first time that the gas circulation naturally forms a donut. Our simulation can also explain various observational features of the system.”

The team says their paper finally explains how donut-shaped structures form around active black holes and, according to Izumi, will “rewrite the astronomy textbooks.”

The paper ” Circumnuclear Multiphase Gas in the Circinus Galaxy. II. The Molecular and Atomic Obscuring Structures Revealed with ALMA” has been published in The Astrophysical Journal.

Aerial view of the Weddell polynya. Credit: Jan Lieser.

Gaping hole larger than the Netherlands opens up in icy sea off Antarctica

An incredibly large area of ice has opened up in the Weddell Sea east of the Antarctic Peninsula, for the second time in 40 years. The phenomenon was previously observed in the same location in the 1970s when satellite imaging was barely making its first baby steps. It’s not clear at this point if the ice hole is influenced in any way by climate change. 

Aerial view of the Weddell polynya. Credit: Jan Lieser.

Aerial view of the Weddell polynya. Credit: Jan Lieser.

Although winter is in full swing right now in Antarctica, a large swath of water in the Weddell sea is ice-free. Such ice-free areas are called ‘polynya’ (Russian) by polar scientists. These occur in the Arctic and Antarctica, typically around the coast. This gaping polynya, which measures an area equivalent to the Netherlands, opened right in the middle of a sea which would have otherwise been completely covered in thick ice.

It’s not that it’s not cold. Temperatures are in their usual frigid range for this time of year. Instead, the Weddel Polynya can be pinned to water stratification in the Southern Ocean, according to scientists at the GEOMAR Helmholtz Centre for Ocean Research who closely following its development.

Satellite image of the polynya. Credit: MODIS-Aqua via NASA Worldview.

Satellite image of the polynya. Credit: MODIS-Aqua via NASA Worldview.

Usually, a very cold but fresh layer of water covers a warmer and saltier layer of water, acting as insulation. In certain conditions, however, the warm water can rise to the surface, melting the ice. “This is like opening a pressure relief valve – the ocean then releases a surplus of heat to the atmosphere for several consecutive winters until the heat reservoir is exhausted,” said  Prof. Dr. Mojib Latif, head of the Research Division at GEOMAR, in a public statement.

The big questions right now are how often such polynya occur and whether or not climate change is amplifying their formation. In situ data is hard to come by but satellite readings will help computer models come up with more precise simulations that might single out culprits. Compared to the last time this happened 40 years ago, scientists have far more data on their hands.

A preliminary analysis run by American scientists suggests that the Weddell Polynya should not occur again because of climate change at all. Due to higher precipitation levels in the region and melting ice, the surface is expected to decouple from deeper water layers. However, previous other studies which applied the “Kiel Climate Model” found that polynya is part of a long-term naturally varying process, which can only mean the hole will open again sooner or later.

“The fact that now a large, ice-free area can be observed in the Weddell Sea confirms our theory and gives us another data point for further model studies,” said Dr. Torge Martin, meteorologist and climate modeler at GEOMAR.

“Global warming is not a linear process and happens on top of internal variability inherent to the climate system. The better we understand these natural processes, the better we can identify the anthropogenic impact on the climate system”, said Professor Latif.

Scientific reference: Mojib Latif et al, Southern Ocean Decadal Variability and Predictability, Current Climate Change Reports (2017). DOI: 10.1007/s40641-017-0068-8

Scientists may have seen a black hole being born for the first time ever

Scientists think they spotted the first-ever glimpse of how black holes form from a former supernova 20 million light-years away.

The Gargantua black hole from Interstellar.
Image credits Double Negative

When massive stars grow old and start running short on fuel, they explode in a dazzling display of light — a supernova. Huge quantities of matter and radiation are shot out at incredible speeds, squishing the core into something so dense that not even light can escape its gravitational pull — a leftover we call a black hole.

That’s what we think happens, anyway — we’ve never actually seen it per se. But now, an Ohio State University of Columbus team led by Christopher Kochanek might have witnessed it. They were combing through data from the Hubble Space Telescope when they observed something strange with the red supergiant star N6946-BH1.

Crunch time

The star was discovered in 2004 and was estimated to be roughly 25 times as massive as the Sun. But when Kochanek and his team looked at snaps taken in 2009, they found that the star flared a to a few million times the brightness of our star for a few months then slowly started to fade away. On the photos Hubble took in the visible spectrum, the star had all but disappeared — the only trace left of its presence is a faint infrared signature.

What happened to N6946-BH1 fits in nicely with what our theories predict should happen when a star its size collapses into a black hole. When it runs out of fuel, the star releases an immense number of neutrinos, so many that it starts losing mass. This in turn weakens its gravitational field, so it starts losing its grip on the cloud of super-heated hydrogen ions enveloping it. As the gas floats away it cools off enough for electrons to re-attach to the hydrogen nuclei.

Now, a star is basically an explosion so massive it keeps itself together under its own weight. Gravity on one hand tries to crunch everything into a point, while the pressure generated by fusion inside the star pushes it outward. While these two are in balance, the star burns away merrily. But once it starts running out of fuel, gravity wins and draws everything together. Matter sinks in the core making it so dense that it collapses in on itself, forming a black hole.

Ironically, it’s gravity that makes stars explode into supernovas — the outer layers are drawn towards the core at such speeds that they bounce off, compacting the core even further. N6946-BH1 didn’t make it to a supernova, but its core did collapse into a black hole. The team theorizes that the flaring we’ve seen is caused by super-heated gas forming an accretion disk around the singularity.

“The event is consistent with the ejection of the envelope of a red supergiant in a failed supernova and the late-time emission could be powered by fallback accretion onto a newly-formed black hole,” the authors write.

We’re still looking for answers

There are two other ways to explain a vanishing star, but they don’t really stand up to scrutiny. N6946-BH1 could have merged with another star — but it should have burned even brighter than before and for longer than a few months — or it could be enveloped in a dust cloud — but it wouldn’t have hidden it for so long.

“It’s an exciting result and long anticipated,” says Stan Woosley at Lick Observatory in California.

“This may be the first direct clue to how the collapse of a star can lead to the formation of a black hole,” says Avi Loeb at Harvard University.

Thankfully, confirming whether or not we’re looking at a black hole isn’t very difficult. The gasses that make up the accretion disk should emit a specific spectrum of X-rays as its being pulled into the black hole, which we can pick up. Kochanek says his group will be getting new data from Chandra X-Ray Observatory sometime in the next two months.

So is this a black hole? Even if they don’t pick up on any X-rays, the team says it doesn’t rule out such an object and that they will continue to look through Hubble – the longer the star is not there, the more likely that it’s a black hole.

“I’m not quite at ‘I’d bet my life on it’ yet,” Kochanek says, “but I’m willing to go for your life.”

The full paper titled “The search for failed supernovae with the Large Binocular Telescope: confirmation of a disappearing star” is still awaiting peer review, and has been published online on arXiv.