NOVA Documentary on Black Holes

Toroid

Founding Member
Tonight on PBS 'Black Hole Apocalypse' Premieres.
'Black Hole Apocalypse' Premieres on PBS Tonight
A new NOVA documentary takes viewers on a virtual journey into a black hole and delves into the exciting new things scientists have learned about the most bizarre places in the universe. The two-hour special "Black Hole Apocalypse" premieres on PBS tonight (Jan. 10) at 9 p.m. ET/8 p.m. CT.

Hosted by astrophysicist Janna Levin of Columbia University, "Black Hole Apocalypse" breaks down the basics of black holes and explains some of the latest groundbreaking discoveries in black hole research. With the help of spectacular computer-generated imagery, Levin leads a virtual tour through the cosmos and straight into a black hole — the point of no return.

Black holes are places in space where the pull of gravity is so strong that nothing, not even light, can escape. In a black hole, the laws of physics as we currently understand them break down. While they're incredibly massive, "black holes aren't objects," Levin explains in the documentary. "Black holes are just nothing. They're empty." [The Strangest Black Holes in the Universe]

If you have a hard time wrapping your head around the concept of a black hole, you're certainly not alone. Black holes are a mind-boggling concept for even the most brilliant astrophysicists. Fortunately, though, you don't need to know anything about black holes or astrophysics to understand the science in "Black Hole Apocalypse." And even black hole experts will be able to appreciate the documentary for its entertainment value alone.

www.youtube.com/watch?v=J7ZN_FxKnSc
Published on Nov 20, 2017
Join astrophysicist Janna Levin and others as they hunt for clues about the nature of black holes. NOVA’s “Black Hole Apocalypse” premieres January 10 on PBS.
 

Toroid

Founding Member
It's now believed that black holes can temporarily bring dead stars back to life.
Cosmic Zombies: Black Holes Can Reanimate Dead Stars
Close encounters with medium-size black holes can reanimate dead stars, if only momentarily, a new study suggests.

A team of astronomers performed computer simulations to determine what happens when a burned-out stellar corpse known as a white dwarf passes close to an intermediate-mass black hole — one that harbors between 1,000 and 10,000 times the mass of Earth's sun.

The researchers determined that the black hole's powerful gravity can stretch and distort the white dwarf's previously inert innards so dramatically that nuclear-fusion processes can reignite for a few seconds, converting helium, carbon and oxygen into heavier elements such as iron. [Images: Black Holes of the Universe]

Such "tidal disruption events" (TDEs) can also generate gravitational waves, the ripples in space-time predicted by Albert Einstein a century ago and first detected directly in 2015 by the Laser Interferometer Gravitational-wave Observatory (LIGO).

LIGO probably cannot pick up these particular gravitational waves, study team members said, but future instruments — such as the European Space Agency's Laser Interferometer Space Antenna, which is scheduled to launch in 2034 — may be able to do so.

And huge amounts of material from extremely disrupted — that is, torn apart — white dwarfs can get sucked in by their killer black holes, sparking powerful radiation bursts that current telescopes are capable of detecting, according to the study.

The new results suggest a possible way to get a better handle on medium-size black holes, which have proven surprisingly difficult to study. Astronomers have found plenty of small (stellar-mass) black holes, and supermassive black holes containing millions or billions of solar masses are known to lurk at the hearts of most, if not all, galaxies. But their intermediate cousins have remained elusive to date.

"It is important to know how many intermediate mass black holes exist, as this will help answer the question of where supermassive black holes come from," study co-author Chris Fragile, a professor of physics and astronomy at the College of Charleston in South Carolina, said in a statement. "Finding intermediate mass black holes through tidal disruption events would be a tremendous advancement."

Supermassive black holes aren't great disruptors, by the way; the behemoths are likely to gobble up a white dwarf before disrupting it appreciably, the researchers wrote.

The new work is of more than just academic interest, for it describes a scenario that our own sun could end up enduring in the far future. Every star that begins its life with about 8 solar masses or fewer will end up as a superdense white dwarf. That fate awaits our sun in 5 billion years or so; after it exhausts its store of hydrogen fuel, it will bloat into a red giant and then collapse into a white dwarf.

The new study has been accepted for publication in The Astrophysical Journal. You can read a copy of it for free at the online preprint site arxiv.org.

www.youtube.com/watch?v=avMuJIvY_8c
 

Toroid

Founding Member
Matter falling into a black hole has been clocked at 30 percent the speed of light.
Matter Falling Into a Black Hole Clocked at 30 Percent the Speed of Light - ExtremeTech
The Royal Astronomical Society has reported the first-ever detection of matter falling directly into a black hole at 30 percent of the speed of light, courtesy of a super-massive black hole located in the galaxy PG211+143. The finding tells us something about how gas is sucked into the gullet of a black hole — and the process is more complicated than you might think.

If you’re reading this site in the first place, you’ve probably got an idea how black holes work. They’re so dense, nothing, not even light, can escape from them. But we can see the light from gas as it plunges towards the black hole, and large concentrations of gas and dust around a black hole is known as an accretion disk. Accretion disks, however, aren’t just passive collections of material streaming straight towards a small black point. They orbit, and at ferocious speeds. These discs also aren’t necessarily cleanly aligned with their black holes, either. Interactions between bands of material can produce different rings moving at different speeds.



Image by K. Pounds et al. / University of Leicester

What the Royal Astronomical Society observers managed to capture was a complex interaction of gases that left some of the material falling straight into the black hole, allowing them to measure its speed. And that speed was phenomenal. From the RAS:

The researchers found the spectra to be strongly red-shifted, showing the observed matter to be falling into the black hole at the enormous speed of 30 percent of the speed of light, or around 100,000 kilometres per second. The gas has almost no rotation around the hole, and is detected extremely close to it in astronomical terms, at a distance of only 20 times the hole’s size (its event horizon, the boundary of the region where escape is no longer possible).

Professor Ken Pounds of the University of Leicester led the effort and used from the ESA’s X-ray observatory XMM-Newton to take readings from the black hole.


“The galaxy we were observing with XMM-Newton has a 40 million solar mass black hole which is very bright and evidently well fed. Indeed some 15 years ago we detected a powerful wind indicating the hole was being over-fed,” Pounds said. “While such winds are now found in many active galaxies, PG1211+143 has now yielded another ‘first’, with the detection of matter plunging directly into the hole itself. We were able to follow an Earth-sized clump of matter for about a day, as it was pulled towards the black hole, accelerating to a third of the velocity of light before being swallowed up by the hole.”

This chaotic accretion pattern could explain how supermassive black holes grow to be such colossal sizes, particularly super black holes in the early universe. The complex interaction between gases in the accretion disc means that more material can be devoured by the black hole in a given period of time. The material falling straight “down” towards the black hole is devoured much more rapidly than material spinning in a tight rotation.
 
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