black holes (5)

Heart of Darkness...


The first direct image of the Milky Way's supermassive black hole shows an orange glowing ring — gas heated as it falls into the singularity — with the shadow of the black hole at the center. EHT Collaboration

Topics: Astrophysics, Black Holes, Cosmology, Einstein, General Relativity

In a triumph of observation and data processing, astronomers at the Event Horizon Telescope have captured the first-ever picture of the supermassive black hole at the center of the Milky Way Galaxy.

The black hole is named Sagittarius A* (pronounced “A-star”), and the reveal of its image received an international rollout this morning in simultaneous press conferences held by the National Science Foundation (NSF) at the National Press Club in Washington, D.C., and the European Southern Observatory headquarters in Garching, Germany.

The image represents 3.5 million gigabytes of data taken at millimeter wavelengths by eight radio telescopes around the world. “It took several years to refine our image and confirm what we had,” said Feryal Özel, an astronomer at the University of Arizona in Tucson, at the NSF press conference. “But we prevailed.”

Blackhole at the center of Milky Way imaged for the first time, Mark Zastrow, Astronomy

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Shadow of Infinity...


Figure 1: A cartoon showing the “self-lensing” of light by a supermassive black hole binary system. Jordy Davelaar and Zoltán Haiman of Columbia University predict that this effect could be used to study black hole binaries that are too far from Earth to probe with other techniques

Topics: Black Holes, Cosmology, Einstein, General Relativity

When galaxies collide, the central supermassive black holes that they contain begin to orbit each other. This supermassive black hole binary attracts gas, which flows through the system to form two disk-shaped structures, one around each of the supermassive black holes. The gas in these “minidisks” heats as it falls toward the holes and begins to radiate light. Astronomers have detected around 150 galaxies with candidate supermassive black hole binaries. And, as observations become more detailed, they expect the light from the minidisks in those systems to bear recognizable, time-dependent signatures from black hole distortions [1]. Now, Jordy Davelaar and Zoltán Haiman of Columbia University have theoretically tested how one such distortion—the “shadow” of the black hole—affects this light signature, finding that it causes a dip in the signal that should be observable in about 1% of candidate systems [23]. The technique could allow astronomers to study black holes that are currently beyond the reach of conventional imaging methods (Fig. 1).

From gravitational-wave measurements of merging black holes to direct imaging of the plasma circling a black hole, the last decade has seen an explosion of observational evidence for black holes (see Viewpoint: The First Sounds of Merging Black Holes and News Feature: Black Hole Imaging Tests Einstein’s Limits) [46]. Yet despite these achievements, many questions remain about black holes, including a critical one: How do black holes grow to supermassive scales—millions to billions of times the mass of the Sun?

A black hole is a simple object, described by its mass, angular momentum, and electrical charge. Supermassive black holes are typically electrically neutral, so their mass and angular momentum parameters determine their gravitational fields. The gravitational field determines how the black holes bend light and thus how they appear to an observer on Earth. Light passing near the black hole is deflected by the gravitational field, producing a black hole shadow—a dark region that is often encircled by a bright light ring—whose size and shape come directly from the black hole’s mass and angular momentum.

Measuring a Black Hole Shadow, George N. Wong, APS Physics

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Rogue Singularity...


A lone black hole gives off no light - but its gravity does distort the path of light traveling around it. Ute Kraus (background Milky Way panorama: Axel Mellinger), Institute of Physics, Universität Hildesheim

Topics: Astrophysics, Black Holes, Cosmology, Einstein, General Relativity

Each second, a brand new baby black hole is born somewhere in the cosmos as a massive star collapses under its own weight.

But black holes themselves are invisible. Historically, astronomers have only been able to detect these stellar-mass black holes when they are acting on a companion.

Now, a team of scientists has made the first-ever confirmed detection of a stellar-mass black hole that’s completely alone. The discovery opens up the possibility of finding even more — an exciting prospect, considering there should be around 100 million such “rogue” black holes drifting through our galaxy unseen.

Relying on the neighbors

Black holes are difficult to find because they don’t shine like stars. Anything with mass warps the fabric of space-time, and the greater the mass, the more extreme the warp. Black holes pack so much mass into such a tiny area that space folds back in on itself. That means that if anything, even light, gets too close, its path will always bend back toward the center of the black hole.

Astronomers have found a couple hundred of these ghostly goliaths indirectly, by seeing how they influence their surroundings. They’ve identified around 20 black holes of the small, stellar-mass variety in our galaxy by watching as stars are devoured by invisible companions. As the black hole pulls matter from its neighbor, the material forms a swirling, glowing accretion disk that signals the black hole’s presence.

Astronomers detect the first potential 'rogue' black hole, Ashley Balzer, Astronomy Magazine

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Cosmic Existentialism...


An illustration of a black hole and its event horizon. (Image credit: Nicholas Forder/Future Publishing)

Topics: Astronomy, Astrophysics, Black Holes, Cosmology, Einstein, General Relativity

"Small" black holes are estimated to make up 1% of the universe's matter.

Scientists have estimated the number of "small" black holes in the universe. And no surprise: It's a lot.

This number might seem impossible to calculate; after all, spotting black holes is not exactly the simplest task. Because there are as pitch-black as the space they lurk in, the light swallowing cosmic goliaths can be detected only under the most extraordinary circumstances — like when they're bending the light around them, snacking on the unfortunate gases and stars that stray too close, or spiraling toward enormous collisions that unleash gravitational waves.

But that hasn't stopped scientists from finding some ingenious ways to guess the number. Using a new method, outlined Jan. 12 in The Astrophysical Journal, a team of astrophysicists has produced a fresh estimate for the number of stellar-mass black holes — those with masses 5 to 10 times that of the sun — in the universe.

And it's astonishing: 40,000,000,000,000,000,000, or 40 quintillions, stellar-mass black holes populate the observable universe, making up approximately 1% of all normal matter, according to the new estimate.

So how did the scientists arrive at that number? By tracking the evolution of stars in our universe they estimated how often the stars — either on their own or paired into binary systems — would transform into black holes, said first author Alex Sicilia, an astrophysicist at the International School of Advanced Studies (SISSA) in Trieste, Italy.

40 quintillion stellar-mass black holes are lurking in the universe, a new study finds, Ben Turner,

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Black Hole Storm...


Topics: Astrophysics, Black Holes, Cosmology, Einstein, General Relativity

Note: From comments on a previous post, maybe science writers need to work on their chosen list of metaphors?

In the far reaches of the Universe, a supermassive black hole is throwing a tantrum.

It's blowing a tremendous wind into intergalactic space, and we're seeing the storm light from 13.1 billion years ago when the Universe was less than 10 percent of its current age. It's the most distant such tempest we've ever identified, and its discovery is a clue that could help astronomers unravel the history of galaxy formation.

"The question is when did galactic winds come into existence in the Universe?" said astronomer Takuma Izumi of the National Astronomical Observatory of Japan (NAOJ).

"This is an important question because it is related to an important problem in astronomy: How did galaxies and supermassive black holes coevolve?"

A Colossal Black Hole Storm Has Been Detected Raging in The Early Universe, Michelle Starr, Science Alert

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