Black Holes in the News

[Recusant]

A couple of recent stories.

"Not long ago, the center of the Milky Way exploded" | ScienceDaily

A titanic, expanding beam of energy sprang from close to the supermassive black hole in the centre of the Milky Way just 3.5 million years ago, sending a cone-shaped burst of radiation through both poles of the Galaxy and out into deep space.

That's the finding arising from research conducted by a team of scientists led by Professor Joss Bland-Hawthorn from Australia's ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) and soon to be published in The Astrophysical Journal.

The phenomenon, known as a Seyfert flare, created two enormous 'ionisation cones' that sliced through the Milky Way -- beginning with a relatively small diameter close to the black hole, and expanding vastly as they exited the Galaxy.

So powerful was the flare that it impacted on the Magellanic Stream -- a long trail of gas extending from nearby dwarf galaxies called the Large and Small Magellanic Clouds. The Magellanic Stream lies at an average 200,000 light years from the Milky Way.

The explosion was too huge, says the Australian-US research team, to have been triggered by anything other than nuclear activity associated with the black hole, known as Sagittarius A, or Sgr A*, which is about 4.2 million times more massive than the Sun.

"The flare must have been a bit like a lighthouse beam," says Professor Bland-Hawthorn, who is also at the University of Sydney.

[Continues . . .

"Black holes stunt growth of dwarf galaxies" | ScienceDaily

Astronomers at the University of California, Riverside, have discovered that powerful winds driven by supermassive black holes in the centers of dwarf galaxies have a significant impact on the evolution of these galaxies by suppressing star formation.

Dwarf galaxies are small galaxies that contain between 100 million to a few billion stars. In contrast, the Milky Way has 200-400 billion stars. Dwarf galaxies are the most abundant galaxy type in the universe and often orbit larger galaxies.

The team of three astronomers was surprised by the strength of the detected winds.

"We expected we would need observations with much higher resolution and sensitivity, and we had planned on obtaining these as a follow-up to our initial observations," said Gabriela Canalizo, a professor of physics and astronomy at UC Riverside, who led the research team. "But we could see the signs strongly and clearly in the initial observations. The winds were stronger than we had anticipated."

Canalizo explained that astronomers have suspected for the past couple of decades that supermassive black holes at the centers of large galaxies can have a profound influence on the way large galaxies grow and age.

"Our findings now indicate that their effect can be just as dramatic, if not more dramatic, in dwarf galaxies in the universe," she said.

[. . .]

"Larger galaxies often form when dwarf galaxies merge together," she said. "Dwarf galaxies are, therefore, useful in understanding how galaxies evolve. Dwarf galaxies are small because after they formed, they somehow avoided merging with other galaxies. Thus, they serve as fossils by revealing what the environment of the early universe was like. Dwarf galaxies are the smallest galaxies in which we are directly seeing winds -- gas flows up to 1,000 kilometers per second -- for the first time."

Manzano-King explained that as material falls into a black hole, it heats up due to friction and strong gravitational fields and releases radiative energy. This energy pushes ambient gas outward from the center of the galaxy into intergalactic space.

"What's interesting is that these winds are being pushed out by active black holes in the six dwarf galaxies rather than by stellar processes such as supernovae," she said. "Typically, winds driven by stellar processes are common in dwarf galaxies and constitute the dominant process for regulating the amount of gas available in dwarf galaxies for forming stars."

Astronomers suspect that when wind emanating from a black hole is pushed out, it compresses the gas ahead of the wind, which can increase star formation. But if all the wind gets expelled from the galaxy's center, gas becomes unavailable and star formation could decrease. The latter appears to be what is occurring in the six dwarf galaxies the researchers identified.

[Continues . . .]

[Michael1]

Didn't know what to reply but here I am, thanks for sharing.

[Recusant]

Really no need to reply, but I appreciate it nonetheless. It's my pleasure to bring interesting stories like this to HAF. 

[Icarus]

I thank you as well Recusant.  Please keep up the most enlightening work.

[Tank]

Iv'e never know you to post something I wasn't interested.

[Red_Cloud]

Really no need to reply.

Well I wont then!

[Red_Cloud]

Iv'e never know you to post something I wasn't interested.

Grovelling creep!

[xSilverPhinx]

There's a documentary by PBS on Netflix called 'NOVA: Black Hole Apocalypse'. It's interesting, even if a little repetitive. 

[xSilverPhinx]

Not so recent, but very important nonetheless!

[Recusant]

Astronomers have made a comprehensive observation of the process of a star being assimilated by a black hole. Insert obligatory sensationalist headline here. 

"Star's Death by Spaghettification: Shredded by Black Hole As Astronomers Record" | SciTech

This animation depicts a star experiencing spaghettification as it's sucked in by a supermassive black hole during a 'tidal disruption event'. In a new study, done with the help of ESO's Very Large Telescope and ESO's New Technology Telescope, a team of astronomers found that when a black hole devours a star, it can launch a powerful blast of material outwards. Credit: ESO/M. Kornmesser

A rare blast of light, emitted by a star as it is sucked in by a supermassive black hole, has been spotted by scientists using telescopes from around the world.

The phenomenon, known as a tidal disruption event, is the closest flare of its kind yet recorded, occurring just 215 million light-years from Earth. It is caused when a star passes too close to a black hole and the extreme gravitational pull from the black hole shreds the star into thin streams of material — a process called 'spaghettification'. During this process some of the material falls into the black hole, releasing a bright flare of energy which astronomers can detect.

Tidal disruption events are rare and not always easy to study because they are usually obscured by a curtain of dust and debris. An international team of scientists led by the University of Birmingham were able to study this event in unprecedented detail because it was detected just a short time after the star was ripped apart.

Using the European Southern Observatory's Very Large Telescope and New Technology Telescope, the Las Cumbres Observatory global telescope network, and the Neil Gehrel's Swift Satellite, the team was able to monitor the flare, named AT2019qiz, over a six-month period as it grew brighter and then faded away.

[Continues . . .]

[Icarus]

Godditit.   

[Randy]

Spaghettification (spelling?) has long been theorized. Now to see it in action is something else.

[Recusant]

I've always found the idea of primordial black holes intriguing. This article does a fair job for a pop-science write-up of the topic via a paper describing what a personal encounter with one of those microscopic nightmare things might entail. I vaguely recall the Niven story mentioned at the beginning, but read it a long time ago.

"What Would Happen if a Tiny Black Hole Passed Through Your Body?" | Universe Today

In 1974, science fiction author Larry Niven wrote a murder mystery with an interesting premise: could you kill a man with a tiny black hole? I won't spoil the story, though I'm willing to bet most people would argue the answer is clearly yes. Intense gravity, tidal forces, and the event horizon would surely lead to a messy end. But it turns out the scientific answer is a bit more interesting.

On the one hand, it's clear that a large enough black hole could kill you. On the other hand, a black hole with the mass of a single hydrogen atom is clearly too small to be noticed. The real question is the critical mass. At what minimum size would a black hole become deadly? That's the focus of a new paper on the arXiv.

The study begins with primordial black holes. These are theoretical bodies that may have formed in the earliest moments of the Universe and would be much smaller than stellar-mass black holes. Anywhere from atom-massed to a mass several times that of Earth. Although astronomers have never found any primordial black holes, observations do rule out several mass ranges. For example, any primordial black hole smaller than 10¹² kg would have already evaporated thanks to Hawking radiation. Anything larger than 10²⁰ kg would gravitationally lens stars in the Milky Way. Since we haven't detected these lensing effects, they must at the very least be exceedingly rare. If they exist at all.

[Continues . . .]

The paper is open access (PDF):

"Gravitational Effects of a Small Primordial Black Hole Passing Through the Human Body" | arXiv

Abstract:

The gravitational effects of a primordial black hole (PBH) passing through the human body are examined, with the goal of determining the minimum mass necessary to produce significant injury or death. Two effects are examined: the damage caused by a shock wave propagating outward from the black hole trajectory, and the dissociation of brain cells from tidal forces produced by the black hole on its passage through the human body.

It is found that the former is the dominant effect, with a cutoff mass for serious injury or death of approximately MPBH > 1.4×10¹⁷g. The number density of primordial black holes with a mass above this cutoff is far too small to produce any observable effects on the human population.

[Icarus]

     ,,,,  contemplating the affect of a black hole..............?????

[zorkan]

https://www.sciencedirect.com/science/article/pii/S0370269321006109 ?