In awe of the size of this black hole. Absolute unit.

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How Big (or Small) Can a Black Hole Get?

For Curiosity:

The biggest astronomy story of 2019 arguably was the first-ever image of a black hole, captured by a world-spanning observatory made up of dozens of telescopes. One big reason this achievement was so astounding is because black holes are relatively tiny compared to their mass: this black hole is 6.5 billion times the mass of our sun, but in overall size, it’s comparable to the size of the solar system. So what sets the size of a black hole, and how big — or small — can they get? And what does the size of a black hole even mean?

[Read the rest at]

Seeing the unseeable: humanity’s first image of a black hole

Yesterday, the Event Horizon Telescope collaboration released the first image of a black hole humanity has ever seen. That simple-looking image represents a century of scientific work: from the first theoretical calculations describing black holes; to the earliest hints that every large galaxy contains a supermassive black hole at its heart; to the technological advances needed to network a world-spanning array of radio telescopes. When I was in college and graduate school, many people thought this very thing was impossible — I know I did. I am happy to say I was wrong then, and this picture of the 6.5 billion solar-mass black hole at the heart of the galaxy M87 is the most thrilling image of my scientific and science-writing career thus far.

the black hole at the center of the M87 galaxy, as seen by the Event Horizon Telescope

The first image humanity has ever captured of a black hole: the supermassive black hole at the heart of the M87 galaxy. [Credit: Event Horizon Telescope]

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The incredible story behind our first image of a black hole

For the first time ever, scientists have captured a direct image of a black hole. The image, captured by the Event Horizon Telescope, allows us to see something that was thought to be invisible


A black hole is invisible by nature. One of the strangest predictions to come out of Albert Einstein’s theory of general relativity, a black hole emits no radiation we can detect, and it swallows up everything that falls on it, matter and light alike. The boundary of a black hole — its event horizon — is a border that can only be crossed from the outside to the inside, not in reverse.

So it might seem paradoxical to talk about capturing an image of a black hole, but this is precisely the mission of the Event Horizon Telescope (EHT). Today, April 10, 2019, will go down in history as the day EHT scientists released the very first direct image of a black hole.

It’s not one in our own Galactic centre, but is at the centre of the galaxy M87 – a resident of the neighbouring Virgo galaxy cluster, which is the home of several trillion stars. The feat marks the first time in history that astronomers have seen the shape of an event horizon. It’s an unprecedented map of gravity at its strongest, involving hundreds of astronomers, engineers, and data scientists from around the world.

[Read the rest at WIRED UK…]

Squeezing light to detect more gravitational waves

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This article appeared in the fall print issue of Popular Science, but I missed that this article had also been published online.

Something called ‘squeezed light’ is about to give us a closer look at cosmic goldmines

Gravitational wave detection is going through an even tighter squeeze.

For Popular Science:

In 2015, scientists caught evidence of a ­cosmic throwdown that took place 1.3 billion light-​years away. They spied this binary black-hole collision by capturing gravitational waves—­ripples in spacetime created when massive objects ­interact—​for the first time. But now physicists want to see even farther. Doing so could help them accurately measure waves cast off by colliding neutron stars, impacts that might be the source of many Earthly elements, including gold. For that, they need the most sensitive gravitational-wave detectors ever.

The devices that nab waves all rely on the same mechanism. The U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO) and its European counterpart, Virgo, fire lasers down two mile-plus-long arms with mirrors at their ends. Passing waves wiggle the mirrors less than the width of an atom, and scientists measure the ripples based on when photons in the laser light bounce off them and come back. Ordinarily, photons exit the lasers at random intervals, so the signals are fuzzy.

[Read the rest at Popular Science]

A black hole in a bathtub and other analog experiments

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Studying impossible systems with analogues

How do you study a phenomenon that cannot be replicated on Earth? You study one that has nothing to do with it, but looks incredibly similar mathematically.

For Physics World:

Some experiments simply can’t be done. It’s a hard truth that physicists learn to face at an early stage in their careers. Some phenomena we want to study require conditions that are out of reach with our current techniques and technologies.

This is especially true when physicists make predictions about the very early universe. Theories hypothesize, for example, that certain particles may have been created during this high-energy period, but our colliders are just not powerful enough to replicate those conditions, which means we cannot create the particles ourselves. The physics that exists only in or around black holes poses a similar problem. Since these massive objects are very far away (the closest known is thousands of light-years distant) and would require hitherto unfeasible amounts of energy to make in the lab, we’re not able to test our theories about them.

[Read the rest at Physics World]

Om nom nom: a black hole ate a star and left crumbs for us to see

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And if I can be shameless: Forbes pays according to traffic, so the more of you who click on the link below and read my stuff, the better they pay me. Ahem.

A Black Hole Ate A Star And Left Crumbs Of Light For Astronomers To Discover

colliding galaxies Arp 299

The colliding galaxies Arp 299, as seen in visible light (the background) and X-rays (red, green, and blue foreground). [Credit: NASA, JPL-Caltech, GSFC, Hubble, NuSTAR]

For Forbes:

Astronomers captured the last moments of an unlucky star that got too close to a black hole. However, they didn’t know that’s what we were seeing right away, because the whole scene of carnage was hidden by clouds of gas and dust. Now, with multiple types of observations and more than ten years of data, we have new insights into the way black holes shred stars, as reported in a new paper in Science.

Black holes, like Cookie Monster, are notoriously messy eaters. That’s good for astronomers, though, because the cosmic crumbs a black hole spills during its meal emit a lot of light. If a star gets too close to a black hole, the gravity tears it to pieces in an act known as “tidal disruption”, but only part of the star’s material actually falls in. (This is a more extreme version of the same forces that raise tides on Earth, and which destroyed a small moon to create Saturn’s rings.) The rest of the star gets channeled into a powerful jet that streams away from the black hole back into space.

[Read the rest at Forbes…]

Why the death of black holes is a big problem for physics

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Part 4 of my 4-part series on black holes for Medium members is up; part 1 is herepart 2 is here, and part 3 is here. If enough of you read, they may keep me around to write more, so please read and share! And yes, the title is a John Donne reference, because I was an English minor and am required to make literary references as often as I can get away with.

Gravity Be Not Proud

The discovery that black holes emit particles and might eventually evaporate threw theoretical physics into chaos. Here’s why.

For Medium:

Hawking ended up being one of the very rare ALS patients to survive the condition, at the eventual cost of being confined to a wheelchair and communicating primarily through a computer. And his work on black holes — along with the work of a small handful of other physicists — opened up a new field of research in quantum gravity.

The most shocking discovery to come out of Hawking’s work: Black holes can emit radiation and can eventually evaporate.

Unfortunately for physicists, the radiation from a real black hole is too faint to be seen, and even a smaller black hole, like the ones seen by LIGO, would take a mind-blowingly long time to evaporate. However, the prediction of this Hawking radiation and death of black holes exposed a major problem in theoretical physics, one that is still unsolved today.

Read the rest at Medium…

Doing astronomy using gravity

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Astronomy without light

Gravitational waves let us see the invisible universe in new ways

For Astronomy Magazine:

Humans have always practiced some form of astronomy. For thousands of years, that meant observing only the light our eyes could see — either unaided or with a variety of instruments, such as astrolabes or telescopes. The 20th century brought new types of telescopes, which detect light we can’t see: infrared, X-ray, and so on.

Today, we’re witnessing the genesis of a whole new type of astronomy, and this one doesn’t use light at all. It uses gravitational waves.

Read the rest at Astronomy Magazine