This Massive Black Hole Is Mysteriously Quiet, And Astronomers Don’t Know Why
“Messier 51, the Whirlpool Galaxy, is one of astronomy’s most spectacular objects. This enormous, face-on galaxy was the first one ever to reveal its spiral structure. The small object alongside it, the galaxy NGC 5195, is interacting and merging with the Whirlpool galaxy. Such mergers trigger new waves of star formation, create grand spiral arms, and activate supermassive black holes.”
That’s the theory, at any rate. Yet when we look at Messier 51, located just outside of the Big Dipper in the night sky, we find that the X-rays being emitted from it are spectacularly minimal. After the Chandra X-ray telescope made its observations, we simply assumed the higher-energy X-rays would make up for the missing radiation, but they show an extreme shortage as well, with neutron stars on the outskirts outshining them.
Perhaps something new is at play. Perhaps active black holes flicker on-and-off faster than we previously thought. There’s a new puzzle, and that means there’s more to learn.
Ask Ethan: What Happens When You Fall Into A Black Hole?
“If you could only know the answer to one question about the Universe, what would you ask? What would you want to know more than anything else? As we get older, most of us lose sight of the things we wondered about as children, which is why I was delighted to get a message from Eric Erb about ten questions that his son, Tristan, brought home from his 2nd grade class. Two of the biggest mysteries of all, gravity and time, dominated his curiosity. After boiling it down, here’s what he wanted to know:
I asked him just now and he wanted two questions to be answered.
1. What happens when you fall into a black hole?
2. Why/how does gravity pull us?
Let’s start at the beginning, and make sure we get to it all.”
If you fell into a black hole, you’d first approach the event horizon from a great distance away, and the light from the Universe around you would start to distort. As you got closer, the event horizon would appear to grow in size faster than you might expect, and the distortions would grow larger in magnitude and color. Time would continue to run at the same, normal speed, and you might not notice crossing the event horizon, but the spaghettifying forces on your body sure would tell you something was up.
Where would you wind up? No one is sure, but the possibilities are both fascinating and terrifying. Find out what happens when you fall into a black hole today.
Merging Neutron Stars Made An Unstoppable Jet, And It Moves At Nearly The Speed Of Light
“How can you make a jet like this? We’ve only ever seen them from one other source: from black holes that are feeding on matter. That must be the clue that solves the puzzle! It isn’t that the merger itself created a jet, but that the completed merger produced a black hole, and this spinning black hole accelerated the matter around it, producing the jets that we saw afterwards. It explains why there was a dimming followed by a second round of brightening, and it explains the collimated structure and the fantastically large energies and speeds. Without a central black hole, there’s no known way to do it.
In science, sometimes the best results are the ones you weren’t expecting. We may have anticipated that merging neutron stars would create the heaviest elements of all, but no one saw a structured jet emerging from a black hole afterwards as something that should occur. Yet here we are, reaping the gifts of the Universe. It’s a reminder from the cosmos to us: the day we stop our scientific inquiries, we stop uncovering the mysteries that underlie our existence.”
On 2017, we saw two neutron stars inspiral and merge together, marking the first time we saw such a thing happen in both gravitational waves and in traditional light signals. But then we kept looking, and noticed something funny: while the light faded away after the explosion, it all of a sudden spiked again in the X-ray and radio parts of the spectrum. It took combining 207 days of data from 32 telescopes across five continents to figure out why, but the culprit is now clear.
There’s a black hole that formed, and it’s powering a jet that all the matter thrown off during the merger cannot stop. Come get the full story today.
2019’s Science Breakthrough Of The Year Will Show Us A Black Hole’s Event Horizon
“Although the Event Horizon Telescope team has detected structure around the black hole at our galaxy’s center, we still don’t have a direct image. This requires understanding our atmosphere and the changes occurring within it, combining the data, and writing novel algorithms to co-process them. It’s a work in progress, but the first half of 2019 is when the final, first images ought to arrive. Some of us were hoping for the images this year or even last year, but it’s most important that we take the time and the care to get it right.
When these images finally do arrive, there will no longer be any doubt as to whether black holes exist, and whether they exist with the properties that Einstein’s greatest theory predicts. 2019 will be the year of the event horizon, and for the first time in all of history, we’ll finally know, conclusively, what they look like.”
All over the world, people are recapping their “best of 2018″ stories, but why limit ourselves to the past? We know, in many cases, what data we’ve collected, what analysis is being done to it, and what we anticipate learning about the Universe from it. Well, one of the big discoveries that’s on the way is the first direct image (possibly two images) of the event horizon of a black hole.
Will what we see agree with Einstein? What direction/orientation will the accretion disk display? Will there be hot spots in the surrounding matter, as expected? And will it have the right size to line up with our other measurements of the black hole’s mass?
Regardless of the outcome, 2019 should be the year of the black hole event horizon! Come find out the incredible science of how.
For The Last Time: The LHC Will Not Make An Earth-Swallowing Black Hole
“To prevent decay, new, unknown physics — for which no evidence exists — must be invoked.
Even if the newly created black hole were stable, it could not devour the Earth. The maximum rate it could consume matter is 1.1 × 10-25 grams-per-second.
It would take 3 trillion years to grow to a mass of 1 kg.”
Well, it was only a matter of time before someone trotted out the long-debunked claim that the LHC could possibly create an Earth-destroying black hole. I, like most of you, just didn’t expect that person to be the esteemed astronomer Sir Martin Rees!
Well, you’ll be happy to know that not only is his claim untrue, but it’s very easy to demonstrate why. You don’t have to point to cosmic rays (which are more energetic and have struck Earth for billions of years) or rely on anything we haven’t already directly observed. In fact, we can even imagine exotic scenarios that could result in the creation of a black hole, and even then, the Earth is entirely safe.
In less than 200 words, you, too, can learn why the LHC will not make an Earth-swallowing black hole. Sorry, all you armchair supervillains out there.
Ask Ethan: Why Is The Black Hole Information Loss Paradox A Problem?
“Why do physicists all seem to agree that the information loss paradox is a real problem? It seems to depend on determinism, which seems incompatible with QM.”
There are a few puzzles in the Universe that we don’t yet know the answer to, and they almost certainly are the harbingers of the next great advances. Solving the mysteries of why there’s more matter than antimatter, what dark matter and dark energy are, or why the fundamental particles have the masses they do will surely bring physics to the next level when we figure them out. One much less obvious puzzle, though, is the black hole information loss paradox. It’s true that we don’t yet have a theory of quantum gravity, but we don’t need one to see why this is a problem. When matter falls into a black hole, something ought to happen to keep it from simply losing its information; entropy must not go down. Similarly, when black holes evaporate, a la Hawking radiation, that information can’t just disappear, either.
So where does it go? Are we poised to violate the second law of thermodynamics? Come find out what the black hole information paradox is all about, and why it compels us to find a solution!
This Is How We Will Successfully Image A Black Hole’s Event Horizon
“Normally, the resolution of your telescope is determined by two factors: the diameter of your telescope and the wavelength of light you’re using to view it. The number of wavelengths of light that fit across your dish determines the optimal angular diameter you can resolve. Yet if this were truly our limits, we’d never see a black hole at all. You’d need a telescope the diameter of the Earth to view even the closest ones in the radio, where black holes emit the strongest and most reliably.
But the trick of very-long baseline interferometry is to view extremely bright sources, simultaneously, from identical telescopes separated by large distances. While they only have the light-gathering power of the surface area of the individual dishes, they can, if a source is bright enough, resolve objects with the resolution of the entire baseline. For the Event Horizon Telescope, that baseline is the diameter of the Earth.”
The Event Horizon Telescope is one of the best examples of international collaboration, and its necessity, in answering questions that are too big for any one nation to do alone. Part of the reason for that is geography: if you want to get the highest-resolution information possible about the Universe, you need the longest-baseline of simultaneous observations that it’s possible to make. That means, if you want to go as hi-res as possible, using the full diameter of the Earth. From the Americas to Eurasia to Africa, Australia and even Antarctica, radio astronomers are all working together to create the first image of a black hole’s event horizon.
What does it look like? Is General Relativity correct? As soon as the Event Horizon Telescope team releases their first images, we’ll know. Come watch a live-blog of a talk from their team today, and get the answers as soon as we know them!
What Happens When Planets, Stars, And Black Holes Collide?
“Brown dwarf collisions. Want to make a star, but you didn’t accumulate enough mass to get there when the gas cloud that created you first collapsed? There’s a second chance available to you! Brown dwarfs are like very massive gas giants, more than a dozen times as massive as Jupiter, that experience strong enough temperatures (about 1,000,000 K) and pressures at their centers to ignite deuterium fusion, but not hydrogen fusion. They produce their own light, they remain relatively cool, and they aren’t quite true stars. Ranging in mass from about 1% to 7.5% of the Sun’s mass, they are the failed stars of the Universe.
But if you have two in a binary system, or two in disparate systems that collide by chance, all of that can change in a flash.”
Nothing in the Universe exists in total isolation. Planets and stars all have a common origin inside of star clusters; galaxies clump and cluster together and are the homes for the smaller masses in the Universe. In an environment such as this, collisions between objects are all but inevitable. We think of space as being extremely sparse, but gravity is always attractive and the Universe sticks around for a long time. Eventually, collisions will occur between planets, stars, stellar remnants, and black holes.
What happens when they run into one another? Unbelievably, we not only know, we have the evidence to back it up!
The Surprising Reason Why Neutron Stars Don’t All Collapse To Form Black Holes
“The measurements of the enormous pressure inside the proton, as well as the distribution of that pressure, show us what’s responsible for preventing the collapse of neutron stars. It’s the internal pressure inside each proton and neutron, arising from the strong force, that holds up neutron stars when white dwarfs have long given out. Determining exactly where that mass threshold is just got a great boost. Rather than solely relying on astrophysical observations, the experimental side of nuclear physics may provide the guidepost we need to theoretically understand where the limits of neutron stars actually lie.”
If you take a large, massive collection of matter and compress it down into a small space, it’s going to attempt to form a black hole. The only thing that can stop it is some sort of internal pressure that pushes back. For stars, that’s thermal, radiation pressure. For white dwarfs, that’s the quantum degeneracy pressure from the electrons. And for neutron stars, there’s quantum degeneracy pressure between the neutrons (or quarks) themselves. Only, if that last case were the only factor at play, neutron stars wouldn’t be able to get more massive than white dwarfs, and there’s strong evidence that they can reach almost twice the Chandrasekhar mass limit of 1.4 solar masses. Instead, there must be a big contribution from the internal pressure each the individual nucleon to resist collapse.
For the first time, we’ve measured that pressure distribution inside the proton, paving the way to understanding why massive neutron stars don’t all form black holes.
This Is Why The Event Horizon Telescope Still Doesn’t Have An Image Of A Black Hole
“Of all the black holes visible from Earth, the largest is at the galactic center: 37 μas.
With a theoretical resolution of 15 μas, the EHT should resolve it.
Despite the incredible news that they’ve detected the black hole’s structure at the galactic center, however, there’s still no direct image.”
Last year, data from the South Pole Telescope, a 10-meter radio telescope located at the South Pole, was added to the Event Horizon Telescope team’s overall set of information. Here we are, though, half a year later, and we still don’t have a direct image of the event horizon for the galactic center’s black hole. There aren’t any problems; the issue is that we have to successfully calibrate and error-correct the data, and that takes time and care to get it right. Science isn’t about getting the answer in the time you have to get it; it’s about getting the right answer in the time it takes to get things right. From that point of view, there’s every reason this is worth waiting for.
The Event Horizon Telescope team is on the right track; here’s where we are right now in our quest to create the first image of a black hole’s event horizon!