black holes – Close Read

Some facts are bigger than numbers – a story

Some facts are just boring, like 1 + 1 = 2. You already knew them before they were presented as such, and now that you do, it’s hard to know what to do with them. Some facts are clearly important, even if you don’t know how you can use them, like the spark plug fires after there’s fuel in the chamber. These two kinds of facts may seem far apart but you also know on some level that by repeatedly applying the first kind of fact in different combinations, to different materials in different circumstances, you get the second (and it’s fun to make this journey).

Then there are some other facts that, while seemingly simple, provoke in your mind profound realisations – not something new as much as a way to understand something deeply, so well, that it’s easy for you to believe that that single neural pathway among the multitude in your head has forever changed. It’s an epiphany.

I came across such a fact this morning when reading an article about a star that may have gone supernova. The author packs the fact into one throwaway sentence.

Roughly every second, one of the observable Universe’s stars dies in a fiery explosion.

The observable universe is 90-something billion lightyears wide. The universe was born only 13.8 billion years ago but it has been expanding since, pushed faster and faster apart by dark energy. This is a vast, vast space – too vast for the human mind to comprehend. I’m not just saying that. Scientists must regularly come up against numbers like 8E50 (8 followed by 50 zeroes), but they don’t have to be concerned about comprehending the full magnitude of those numbers. They don’t need to know how big it is in some dimension. They have the tools – formulae, laws, equations, etc. – to tame those numbers into submission, to beat them into discoveries and predictions that can be put to human use. (Then again, they do need to deal with monstrous moonshine.)

But for the rest of us, the untameability can be terrifying. How big is a number like 8E50? In kilograms, it’s about a 100-times lower than the mass of the observable universe. It’s the estimated volume of the galaxy NGC 1705 in cubic metres. It’s approximately the lifespan of a black hole with the mass of the Sun. You know these facts, yet you don’t know them. They’re true but they’re also very, very big, so big that they’re well past the point of true comprehension, into the realm of the I’d-rather-not-know. Yet the sentence above affords a way to bring these numbers back.

The author writes that every second or so, a star goes supernova. According to one estimate, 0.1% of stars have enough mass to eventually become a black hole. The observable universe has 200 billion trillion stars. This means there are 2E20 stars in the universe that could become a black hole, if they’re not already. Considering the universe has lived around 38% of its life and assuming a uniform rate of black hole formation (a big assumption but should suffice to illustrate my point), the universe should be visibly darkening by now, considering photons of light shouldn’t have to travel much before encountering a black hole.

But it isn’t. The simple reason is that that’s how big the universe is. We learn about stars, other plants, black holes, nebulae, galaxies and so forth. There are lots and lots of them, sure, but you know what there is the most of? The things we often discuss the least: the interstellar medium, the space between stars, and the intergalactic medium, the space between galaxies. Places where there isn’t anything big enough, ironically, to be able to catch the popular imagination. One calculation, based on three assumptions, suggests matter occupies an incomprehensibly low fraction of the observable universe (1. 85% of this is supposed to be dark matter; 2. please don’t assume atoms are also mostly empty).

In numbers, the bigness of all this transcends comprehension – but knowing that billions upon billions of black holes still only trap a tiny amount of the light going around can be… sobering. And enlivening. Why, in the time you’ve taken to read this article, 300 more black holes will have formed. Pfft.

The Government Project

Considering how much the Government of India has missed anticipating – the rise of a second wave of COVID-19 infections, the crippling medical oxygen shortage, the circulation of new variants of concern – I have been wondering about why we assemble giant institutions like governments: among other things, they are to weather uncertainty as best as our resources and constitutional moralities will allow. Does this mean bigger the institution, the farther into the future it will be able to see? (I’m assuming here a heuristic that we normally are able to see, say, a day into the future with 51% uncertainty – slightly better than chance – for each event in this period.)

Imagine behemoth structures like the revamped Central Vista in New Delhi and other stonier buildings in other cities and towns, the tentacles of state control dictating terms in every conceivable niche of daily life, and a prodigious bureaucracy manifested as tens of thousands of civil servants most of whom do nothing more than play musical chairs with The Paperwork.

Can such a super-institution see farther into the future? It should be able to, I’d expect, considering the future – in one telling – is mostly history filtered through our knowledge, imagination, priorities and memories in the present. A larger government should be able to achieve this feat by amassing the talents of more people in its employ, labouring in more and more fields of study and experiment, effectively shining millions of tiny torchlights into the great dark of what’s to come.

Imagine one day that the Super Government’s structures grow so big, so vast that all the ministers determine to float it off into space, to give it as much room as it needs to expand, so that it may perform its mysterious duties better – something like the City of a Thousand Planets.

The people of Earth watch as the extraterrestrial body grows bigger and bigger, heavier and heavier. It attracts the attention of aliens, who are bemused and write in their notebooks: “One could, in principle, imagine ‘creatures’ that are far larger. If we draw on Landauer’s principle describing the minimum energy for computation, and if we assume that the energy resources of an ultra-massive, ultra-slothful, multi-cellular organism are devoted only to slowly reproducing its cells, we find that problems of mechanical support outstrip heat transport as the ultimate limiting factor to growth. At these scales, though, it becomes unclear what such a creature would do, or how it might have evolved.”

One day, after many years of attaching thousands of additional rooms, corridors, cabinets and canteens to its corse, the government emits a gigantic creaking sound, and collapses into a black hole. On the outside, black holes are dull: they just pull things towards them. That the pulled things undergo mind-boggling distortions and eventual disintegration is a triviality. The fun part is what happens on the inside – where spacetime, instead of being an infinite fabric, is curved in on itself. Here, time moves sideways, perpendicular to the direction in which it flows on the outside, in a state of “perpetual freefall”. The torch-wielding scientists, managers, IAS officers, teachers, thinkers are all trapped on the inner surface of a relentless sphere, running round and round, shining their lights to look not into the actual future but to find their way within the government itself.

None of them can turn around to see who it is that’s chasing them, or whom they’re chasing. The future is lost to them. Their knowledge of history is only marginally better: they have books to tell them what happened, according to a few historians at one point of time; they can’t know what the future can teach us about history. And what they already know they constantly mix and remix until, someday, like the progeny of generations of incest, what emerges is a disgusting object of fascination.

The government project is complete: it is so big that it can no longer see past itself.

The weekly linklist – July 25, 2020

I’ve decided to publish this linklist via Substack. Next weekend onwards, it will only be available on https://linklist.substack.com. And this is why the list exists and what kind of articles you can find in it.

Want to buy a parrot? Please login via Facebook. – “F-commerce emerged in Bangladesh largely because there was no major e-commerce platform to absorb all the business. But although it’s biggest there, this form of selling isn’t exclusive to the country, or even the region: globally, 160 million small stores operate on Facebook, and in countries like Thailand, almost half of all online sales happen through social media.”
The history of climate science – “The fact that carbon dioxide is a ‘greenhouse gas’ – a gas that prevents a certain amount of heat radiation escaping back to space and thus maintains a generally warm climate on Earth, goes back to an idea that was first conceived, though not specifically with respect to CO2, nearly 200 years ago. The story of how this important physical property was discovered, how its role in the geological past was evaluated and how we came to understand that its increased concentration, via fossil fuel burning, would adversely affect our future, covers about two centuries of enquiry, discovery, innovation and problem-solving.”
The story of cryptomining in Europe’s most disputed state – “In early 2018, millions of digital clocks across Europe began falling behind time. Few took notice at first as slight disruptions in the power supply caused bedside alarms and oven timers running on the frequency of electric current to begin lagging. … European authorities soon traced the power fluctuations to North Kosovo, a region commonly described as one of Europe’s last ganglands. Since 2015, its major city, Mitrovica, has been under the control of Srpska Lista, a mafia masquerading as a political party. Around the time Srpska came to power, North Kosovo’s electricity consumption surged. Officials at the Kosovo Electricity Supply Company in Prishtina, Kosovo’s capital city, told me that the region now requires 20 percent more power than it did five years ago. Eventually, it became clear why: across the region, from the shabby apartment blocks of Mitrovica to the cellars of mountain villages, Bitcoin and Ethereum rigs were humming away, fueling a shadow economy of cryptocurrency manufacturing.”
Electromagnetic pulses are the last thing you need to worry about in a nuclear explosion – “The electromagnetic pulse that comes from the sundering of an atom, potentially destroying electronics within the blast radius with some impact miles away from ground zero, is just one of many effects of every nuclear blast. What is peculiar about these pulses, often referred to as EMPs, is the way the side effect of a nuclear blast is treated as a special threat in its own right by bodies such as the Task Force on National and Homeland Security, which, despite the official-sounding name, is a privately funded group. These groups continue a decadelong tradition of obsession over EMPs, one President Donald Trump and others have picked up on.”
India’s daunting challenge: There’s water everywhere, and nowhere – “I am walking across the world. Over the past seven years I have retraced the footsteps of Homo sapiens, who roamed out of Africa in the Stone Age and explored the primordial world. En route, I gather stories. And nowhere on my foot journey—not in any other nation or continent—have I encountered an environmental reckoning on the scale of India’s looming water crisis. It is almost too daunting to contemplate.”
Here be black holes – “During the 15th and 16th centuries, when oceans were the spaces between worlds, marine animals, often so prodigious that they were termed sea monsters, were difficult to see and even harder to analyse, their very existence uncertain. Broadly construed, the history of space science is also a story of looking across and into the ocean – that first great expanse of space rendered almost unknowable by an alien environment. Deep space, like the deep sea, is almost inaccessible, with the metaphorical depth of space echoing the literal depth of oceans. These cognitive and psychic parallels also have an analogue in the practicalities of survival, and training for space missions routinely includes stints under water.”
Birds bear the warnings but humans are responsible for the global threat – “Bird omens of a sort are the subject of two recent anthropological studies of avian flu preparedness in Asia. Both Natalie Porter, in Viral Economies, and Frédéric Keck, in Avian Reservoirs, convey the ominousness suffusing poultry farming, using birds as predictors. As both demonstrate, studying how birds interact with human agriculture can provide early warnings of a grim future. Indeed, Keck in Avian Reservoirs explicitly compares public-health surveillance (which he studies in the book) to augury, tracing ‘the idea that birds carry signs of the future that humans should learn to read … back to Roman divination.'”
Fiction as a window into the ethics of testing the Bomb – “The stuff that surprised me was on the American side. For example, the assessment by Curtis LeMay [the commander who led US air attacks on Japan] where he basically says, “We’ve bombed the shit out of Japan. Hurry up with your atomic bomb, because there’s going to be nothing left if you don’t.” That shocked me, and also that they deliberately left those cities pristine because they wanted to show the devastation. They wanted, I believe, to kill innocent people, because they were already moving on to the Cold War.”
The idea of entropy has led us astray – “Perhaps physics, in all its rigors, is deemed less susceptible to social involvement. In truth, though, Darwinian and thermodynamic theories served jointly to furnish a propitious worldview—a suitable ur-myth about the universe—for a society committed to laissez-faire competition, entrepreneurialism, and expanding industry. Essentially, under this view, the world slouches naturally toward a deathly cold state of disorder, but it can be salvaged—illuminated and organized—by the competitive scrabble of creatures fighting to survive and get ahead.”
How massive neutrinos broke the Standard Model – “Niels Bohr … had the radical suggestion that maybe energy and momentum weren’t really conserved; maybe they could somehow be lost. But Wolfgang Pauli had a different — arguably, even more radical — thought: that perhaps there was a novel type of particle being emitted in these decays, one that we simply didn’t yet have the capacity to see. He named it “neutrino,” which is Italian for “little neutral one,” and upon hypothesizing it, remarked upon the heresy he had committed: ‘I have done a terrible thing, I have postulated a particle that cannot be detected.'”
How a small Arab nation built a Mars mission from scratch in six years – “When the UAE announced in 2014 that it would send a mission to Mars by the country’s 50th birthday in December 2021, it looked like a bet with astronomically tough odds. At the time, the nation had no space agency and no planetary scientists, and had only recently launched its first satellite. The rapidly assembled team of engineers, with an average age of 27, frequently heard the same jibe. ‘You guys are a bunch of kids. How are you going to reach Mars?’ says Sarah Al Amiri, originally a computer engineer and the science lead for the project.”
The pandemic has made concentrated reading difficult. How are book reviewers dealing with this? – “To read good and proper, I needed to disconnect from the terrible reality of the present – wishful thinking with the always-on-alert mode that the pandemic thrust upon us. A few pages in, my mind would wander, snapping out of the brief, quiet moment and I’d find myself reaching for my phone. … But as neuroscientists world over have told us, it’s been hard for most people to focus, with our brain in fight-or-flight mode to the threat of the virus. An activity like deep reading is especially difficult because it requires a high level of engagement and quiet. So it wasn’t just me.”
Facebook’s employees reckon with the social network they’ve built – “Why was Zuckerberg only talking about whether Trump’s comments fit the company’s rules, and not about fixing policies that allowed for threats that could hurt people in the first place, he asked. ‘Watching this just felt like someone was sort of slowly swapping out the rug from under my feet,’ Wang said. ‘They were swapping concerns about morals or justice or norms with this concern about consistency and logic, as if it were obviously the case that ‘consistency’ is what mattered most.'”

All the science in ‘The Cloverfield Paradox’

I watched The Cloverfield Paradox last night, the horror film that Paramount pictures had dumped with Netflix and which was then released by Netflix on February 4. It’s a dumb production: unlike H.R. Giger’s existential, visceral horrors that I so admire, The Cloverfield Paradox is all about things going bump in the dark. But what sets these things off in the film is quite interesting: a particle accelerator. However, given how bad the film was, the screenwriter seems to have used this device simply as a plot device, nothing else.

The particle accelerator is called Shepard. We don’t know what particles it’s accelerating or up to what centre-of-mass collision energy. However, the film’s premise rests on the possibility that a particle accelerator can open up windows into other dimensions. The Cloverfield Paradox needs this because, according to its story, Earth has run out of energy sources in 2028 and countries are threatening ground invasions for the last of the oil, so scientists assemble a giant particle accelerator in space to tap into energy sources in other dimensions.

Considering 2028 is only a decade from now – when the Sun will still be shining bright as ever in the sky – and renewable sources of energy aren’t even being discussed, the movie segues from sci-fi into fantasy right there.

Anyway, the idea that a particle accelerator can open up ‘portals’ into other dimensions isn’t new nor entirely silly. Broadly, an accelerator’s purpose is founded on three concepts: the special theory of relativity (SR), particle decay and the wavefunction of quantum mechanics.

According to SR, mass and energy can transform into each other as well as that objects moving closer to the speed of light will become more massive, thus more energetic. Particle decay is what happens when a heavier subatomic particle decomposes into groups of lighter particles because it’s unstable. Put these two ideas together and you have a part of the answer: accelerators accelerate particles to extremely high velocities, the particles become more massive, ergo more energetic, and the excess energy condenses out at some point as other particles.

Next, in quantum mechanics, the wavefunction is a mathematical function: when you solve it based on what information you have available, the answer spit out by one kind of the function gives the probability that a particular particle exists at some point in the spacetime continuum. It’s called a wavefunction because the function describes a wave, and like all waves, this one also has a wavelength and an amplitude. However, the wavelength here describes the distance across which the particle will manifest. Because energy is directly proportional to frequency (E = h × ν; h is Planck’s constant) and frequency is inversely proportional to the wavelength, energy is inversely proportional to wavelength. So the more the energy a particle accelerator achieves, the smaller the part of spacetime the particles will have a chance of probing.

Spoilers ahead

SR, particle decay and the properties of the wavefunction together imply that if the Shepard is able to achieve a suitably high energy of acceleration, it will be able to touch upon an exceedingly small part of spacetime. But why, as it happens in The Cloverfield Paradox, would this open a window into another universe?

Spoilers end

Instead of directly offering a peek into alternate universes, a very-high-energy particle accelerator could offer a peek into higher dimensions. According to some theories of physics, there are many higher dimensions even though humankind may have access only to four (three of space and one of time). The reason they should even exist is to be able to solve some conundrums that have evaded explanation. For example, according to Kaluza-Klein theory (one of the precursors of string theory), the force of gravity is so much weaker than the other three fundamental forces (strong nuclear, weak nuclear and electromagnetic) because it exists in five dimensions. So when you experience it in just four dimensions, its effects are subdued.

Where are these dimensions? Per string theory, for example, they are extremely compactified, i.e. accessible only over incredibly short distances, because they are thought to be curled up on themselves. According to Oskar Klein (one half of ‘Kaluza-Klein’, the other half being Theodore Kaluza), this region of space could be a circle of radius 10^-32 m. That’s 0.00000000000000000000000000000001 m – over five quadrillion times smaller than a proton. According to CERN, which hosts the Large Hadron Collider (LHC), a particle accelerated to 10 TeV can probe a distance of 10^-19 m. That’s still one trillion times larger than where the Kaluza-Klein fifth dimension is supposed to be curled up. The LHC has been able to accelerate particles to 8 TeV.

The likelihood of a particle accelerator tossing us into an alternate universe entirely is a different kind of problem. For one, we have no clue where the connections between alternate universes are nor how they can be accessed. In Nolan’s Interstellar (2014), a wormhole is discovered by the protagonist to exist inside a blackhole – a hypothesis we currently don’t have any way of verifying. Moreover, though the LHC is supposed to be able to create microscopic blackholes, they have a 0% chance of growing to possess the size or potential of Interstellar‘s Gargantua.

In all, The Cloverfield Paradox is a waste of time. In the 2016 film Spectral – also released by Netflix – the science is overwrought, stretched beyond its possibilities, but still stays close to the basic principles. For example, the antagonists in Spectral are creatures made entirely as Bose-Einstein condensates. How this was even achieved boggles the mind, but the creatures have the same physical properties that the condensates do. In The Cloverfield Paradox, however, the accelerator is a convenient insertion into a bland story, an abuse of the opportunities that physics of this complexity offers. The writers might as well have said all the characters blinked and found themselves in a different universe.

The journey of a crow and the story of a black hole

The Washington Post has a review, and introduction therewith, of a curious new book called Ka, authored by John Crowley (acclaimed author of Great Work of Time). It is narrated from the POV of a crow named Dar Oakley, who journeys repeatedly into the realm of the dead with a human companion. A para from the WaPo piece caught my attention for its allusion to an unsolved problem in physics:

In many cultures, crows have long been regarded as “death-birds.” Eaters of carrion and corpses, they are sometimes even said to convey the soul into the afterlife. Crowley’s title itself alludes to this notion: Dar Oakley croaks out “ka,” which isn’t just a variant spelling of “caw,” but also the ancient Egyptian word for the spiritual self that survives the decay of the body. Yet what actually remains of us after our bones have been picked clean? Might our spirits then dwell in some Happy Valley or will we suffer in eternal torment? Could death itself be simply an adventure-rich dream from which we never awake? Who knows? The narrator, who might be a writer, says of his dead and much-missed wife Debra that “the ultimate continuation of her is me.” What, however, becomes of Debra when he too is dead?

What indeed. The question is left unanswered so the reader can confront the unanswerability supposedly implicit in this riddle. But while this scheme may be acceptable in a book-length “exploration of the bond between the living and the dead”, physicists don’t have much of a choice. They really want to know, would love to know, how a very similar situation plays out in the quantum realm.

It’s called the black hole information paradox. A black hole is a single point in space around which spacetime is folded into a sphere. This means that if you get trapped in this region of spacetime, you’re locked in. You can’t leave the sphere. The surface of this sphere is called the event horizon: it’s the shortest distance from the black hole from which you can pull away.

Now, there’s no way to tell two black holes apart if their mass, angular momentum and electric charge are the same. This is called the no-hair conjecture. This means that whatever a black hole swallows – whether it be physical matter or information as a sequence of 0s and 1s encoded as an electromagnetic signal – doesn’t retain its original shape or patterns. They become lost, observable only in changes to the black hole’s mass, angular momentum and/or electric charge.

In 1974, Stephen Hawking, Alexei Starobinsky and Yakov Zel’dovich found that, thanks to quantum mechanical effects near an event horizon, the black hole within could be emitting radiation out into space. So assuming a black hole contains a finite amount of energy and has stopped eating material/info from the outside, it will evaporate slowly over time and vanish. This is where the information paradox kicks in.

You’re obviously thinking the info the black hole once swallowed was all converted into energy and emitted as Hawking radiation. This is actually where the problem begins. Quantum mechanics may be whimsically counterintuitive about what it allows nature to do at its smallest scale. But it does have some rules of its own that it always follows. One of them is that information is always conserved, that when information passes into a black hole, it can’t be converted into the same energy mulch that everything else is converted to.

We don’t know what happens to the ‘spirit’ of Debra when Dar Oakley passes away. And we don’t know what happens to the information inside a black hole when the latter evaporates.

Black holes are unique objects of study for classical and non-classical physicists alike because they combine the consequences of both general relativity and quantum mechanics. Those pursuing a unified theory, broadly called quantum gravity, hope that data about black holes will help them find a way to reconcile the laws of nature at the biggest and smallest scales. Resolving the black hole information paradox is one such path.

For example, string theory, which is a technical framework that gives physicists and mathematicians the tools to solve problems in quantum gravity, proposes a way out in the name of the holographic principle. It states (in highly simplified terms) that the information trapped by a black hole is actually trapped along the event horizon and doesn’t fall inside it. Over time, fluctuations on the horizon release the information out. However, neither the complete shape and consequences of this theory nor some contradictory predictions are fully understood.

Even whether humans will be able to resolve this paradox in their lifetime at all remains to be seen – but it’s important to hope that such a thing is possible and that the story of a black hole’s life can be told from start to finish someday. Crowley also tries to answer Dar Oakley’s question about Debra’s fate thus (according to the WaPo review):

“Maybe not, said the Skeleton. But look at it this way. When you return home, you’ll tell the story of how you sought it and failed, and that story will be told and told again. And when you’re dead yourself, the story will go on being told, and in that telling you’ll speak and act and be alive again.”

Caw!

Featured image credit: Free-Photos/pixabay.

Neutron stars

When the hype for the announcement of the previous GW detection was ramping up, I had a feeling LIGO was about to announce the detection of a neutron-star collision. It wasn’t to be – but in my excitement, I’d written a small part of the article. I’m sharing it below. I’d also recommend reading this post: The Secrets of How Planets Form.

Stars die. Sometimes, when that happens, their outer layers explode into space in a supernova. Their inner layers collapse inwards under the gravity of their own weight in a violent rush. If the starstuff can be packed dense enough, the collapse produces a blackhole – a volume of space where the laws of quantum mechanics and relativity break down and the particles of matter are plunged into a monumental identity crisis. However, if the dying star wasn’t heavy enough when it blew up, then the inward rush will create a very, very, very dense object – but not a blackhole: a neutron star.

Neutron stars are the densest objects in the universe that astronomers can observe. The only things we know are denser than them are blackholes.

You’d think observed means ‘saw’, but what is ‘seeing’ but the light – a form of electromagnetic energy – from an event reaching our eyes? We can’t directly ‘see’ blackholes collide because the collision doesn’t release any electromagnetic energy. So astronomers have built a special kind of eyes – called gravitational wave detectors – that can observe ripples of gravitational energy that the collision lets loose.

The Laser Interferometer Gravitational-wave Detector (LIGO) we already know about. Its twin eyes, located in Washington and Louisiana, US, have detected three blackhole-blackhole collisions thus far. Two of the scientists who helped build it are hot favourites to win the Nobel Prize for physics next week. The other set of eyes involved in the last find is Virgo, a detector in Italy.

You’ve been told that blackholes are freaks of nature. Heavy objects bend spacetime around themselves. Blackholes are freaks because they step it up: they fold it. They’re so heavy that when spacetime bends around them, it goes all the way around and becomes a three-dimensional loop. Thus, a blackhole traps one patch of the cosmos around a vanishingly small heart of darkness. Even light, if it comes close enough, becomes trapped in this loop and can never escape. This is why astronomers can’t observe blackholes directly, and use gravitational-wave detectors instead.

But neutron stars they can observe. They’re exactly what their names suggest: a ball of neutrons. And neutrons experience a force of nature called the strong nuclear force, and it can be 100,000 billion billion billion times stronger than gravity. This makes neutron stars extremely dense and altogether incredibly heavy as well. On their surface, a classic can of Coke will weigh 355,000 billion tonnes, a thousand-times heavier than all the humans on Earth combined.

Sometimes, a neutron star is ravaged by a powerful magnetic field. This field focuses charged particles on the neutron star’s surface into a tight beam of radiation shooting off into space. If the orb is also spinning, then this beam of radiation sweeps through space like the light from a lighthouse sweeps over the sea near it. Such neutron stars are called pulsars.

Ironing out an X-ray wrinkle

A version of this post, as written by me, originally appeared in The Copernican science blog on March 1, 2013.

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One of the techniques to look for and measure the properties of a black hole is to spot X-rays of specific energies coming from a seemingly localized source. The radiation emanates from heated objects like gas molecules and dust particles in the accretion disc around the black hole that have been compressed and heated to very high temperatures as the black hole prepares to gorge on them.

However, the X-rays are often obscured by gas clouds surrounding the black hole, even at farther distances, and then other objects on the path of its long journey to Earth. And this is a planet whose closest black hole is 246 quadrillion km away. This is why the better telescopes that study X-rays are often in orbit around Earth instead of on the ground to minimize further distortions due to our atmosphere.

NASA’s NuSTAR

One of the most powerful such X-ray telescopes is NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array), and on February 28, the government body released data from the orbiting eye almost a year after it was launched in June 2012. NuSTAR studies higher-energy the sources and properties of higher-energy X-rays in space. In this task, it is also complemented by the ESA’s XMM-Newton space-telescope, which studies lower-energy X-rays.

The latest data concerns the black hole at the centre of the galaxy NGC 1365, which is two million times the mass of our Sun, earning it the title of Supermassive Black Hole (SMBH). Around this black hole is an accretion disc, a swirling vortex of gases, metals, molecules, basically anything unfortunate enough to have come close and subsequently been ripped apart. Out of this, NuSTAR and XMM-Newton zeroed in on the X-ray emissions characteristic of iron.

What the data revealed, as has been the wont of technology these days, is a surprise.

What are signatures for?

Emission signatures are used because we know everything about them and we know what makes each one unique. For instance, knowing the rise and dip of X-ray brightness coming from an object at different temperatures allows us to tell whether the source is iron or something else.

By extension, knowing that the source is iron lets us attribute the signature’s distortions to different causes.

And the NuSTAR data has provided the first experimental proof that iron’s signature’s distortion is not due to gas-obscuration, but due to another model called prograde rotation which attributes the distortion to the black hole’s gravitational pull.

A clearer picture

As scientists undertake a detailed analysis of the NASA data, they will also resolve iron’s signature. This means the plot of its emissions at different temperatures and times will be split up into different “colours” (i.e., frequencies) to see how much each colour has been distorted.

With NuSTAR in the picture, this analysis will assume its most precise avatar yet because the telescope’s ability to track higher-energy X-rays lets it penetrate well enough into the gas clouds around black holes, something that optical telescopes like the one at the Keck Observatory can’t. What’s more, the data will also be complete at the higher-energy levels, earlier left blank because XMM-Newton or NASA’s Chandra couldn’t see in that part of the spectrum.

If the prograde rotation model is conclusively proven after continued analysis and more measurements, then for the first time, scientists will have a precision-measurement tool on their hands to calculated black hole spin.

How? If the X-ray distortions are due to the black hole’s gravitational pull and nothing else, then the rate of its spin should be showing itself as the amount of distortion in the emission signature. The finer details for this can be picked out from the resolved data, and a black hole’s exact spin for the first time be pinned down.

The singularity

NGC 1365 is a spiral galaxy about 60 million light-years in the direction of the constellation Fornax and a prominent member of the much-studied Fornax galaxy cluster. Apart from the black hole, the galaxy hosts other interesting features such as a central bar of gas and dust adjacent to prominent star-forming regions and a type-1a supernova discovered as recently as October 27, 2012.

As we sit here, I can’t help but imagine us peering into our tiny telescopes, picking up on feebly small bits of information, and adding an extra line in our textbooks, but in reality being thrust into an entirely new realm of knowledge, understanding, and awareness.

Now, we know there’s a black hole out there – a veritable freak of nature – spinning as fast as the general theory of relativity will allow!