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Black holes

Matter and even entire stars fall into a black hole. Illustration: depositphotos.com

Astronomers think they've spotted an 'invisible' black hole for the first time

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Holes were able to detect a black hole that matter does not fall into or is not part of a binary system, thus it is not exposed to the eye and to almost any other instrument * Some telescopes that are under construction or ready to be used will be able to detect such individual black holes on a daily basis
Gravitational waves. Illustration: depositphotos.com

Discovering dark matter: New clue from mysterious clouds around swirling black holes

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Very light boson particles are a new type of subatomic particle that scientists have proposed as a compelling possibility for dark matter. But these very light particles, if they exist, are difficult to detect because their mass is very small and only rarely do they create interactions with other matter, this is one of the important properties of dark matter
It is a complex picture of X-rays, molecular gas and hot ionized gas near the center of the galaxy. The orange shapes are glowing hydrogen gas. One of these shapes, at the upper end of the jet (see an illuminated image below) is interpreted as a hydrogen cloud that was hit by the jet and moved outward. The jet disperses the cloud into tendrils that move towards the north. Further down near the black hole are X-ray observations of highly heated gas in blue and molecular gas in green. These data are evidence that the black hole is occasionally accreted by stars or gas clouds, and is ejecting some of the very hot material along its axis of rotation. Credit: NASA, ESA, and Gerald Cecil (UNC-Chapel Hill); Image Processing: Joseph DePasquale (STScI)

The Milky Way's supermassive black hole is still humming long after a burst of powerful 'death rays'

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The Hubble Space Telescope photographed a bright knot of gas hit by an invisible jet from the black hole, which is only 15 light years away. The black hole must have looked bright billions of years ago as a quasar, when our young galaxy was fed by lots of infalling gas. But after all this time the black hole is acting sporadically, unwilling to take a nap
A black hole swallows its companion star. Illustration: shutterstock

Two gravitational wave events within 10 days: black holes have been discovered that eat neutron stars - "like Pac-Man"

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The Laser Interferometer Gravitational Wave Observatory (LIGO) in the US and the Virago Gravitational Wave Observatory in Italy captured the gravitational waves from the death spiral and merger of a neutron star with a black hole, not once but twice. The findings were recently published in The Astrophysical Journal Letters

The quantum mechanics of black holes

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A black hole is a mysterious celestial body. Einstein's theory of relativity taught us a lot about black holes, but many question marks remain about what goes on inside. It is likely that the picture will become clearer as soon as a quantum theory of gravity is discovered, but until then we will content ourselves with the collision of quantum mechanics and general relativity around the event horizon. In this chapter we will discuss the paradox that arose from this collision, the multitude of published solutions and the fascinating developments of the past two years
A black hole with a warped disk. Credit: John Paice

A strange black hole with a massive distortion in its accretion disk has been discovered

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An international team of astrophysicists from South Africa, the UK, France and the US have found a large variation in the brightness of light seen around one of the closest black holes in our galaxy, 9,600 light-years from Earth, and they conclude that it is caused by a massive distortion in its accretion disk
The top left image is a radio image from 1997. The lower left is a photo of the same spot from 2017, where the new radio source is clearly visible. The image on the right is a visible light image taken by the Hubble Space Telescope, where you can see the galaxy where the supernova occurred (photo: from the study). Courtesy of the Hebrew University and Tel Aviv University

Double cosmic cannibalism - a huge explosion in space shed light on an astronomical mystery

A new international study with the participation of researchers from Tel Aviv University and the Hebrew University confirmed for the first time the existence of the phenomenon of "double cosmic cannibalism" - a rare phenomenon in which a star swallows a compressed object such as a black hole or a neutron star, and the object in turn "devours" the core of the star. The end of the destructive process in a huge explosion in the center of which apparently remains a black hole
The galaxy M87. Artist illustration. shutterstock

New research: Why is dark matter - the main component of matter in the universe - absent in some galaxies?

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A simulation of a tidal disruption event, from the research of Elad Steinberg from the Hebrew University

An interaction between a black hole and a star has revealed a new type of black hole

A joint study by a pair of researchers from the Hebrew University and Arizona presents a new way to discover the location of medium-sized black holes in the universe. With the help of a reanalysis of X-ray data and observations, the researchers were able to measure for the first time the speed at which the medium-sized black hole rotates, creating an opening for further discoveries and research in the field
A neutron star just before merging with the black hole. Image: Carl Knox OzGrav/Swinburne University of Technology

Astronomers discovered a merger of a black hole and a neutron star, then another just ten days later

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A rare event that occurred in January 2020 still fascinates scientists, who are trying to learn about the structure of the neutron star with its help
A jet emitted from a black hole at the center of a galaxy. Illustration: shutterstock

Why supermassive black holes keep growing at the centers of massive galaxies

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Researchers from the Hebrew University and France discovered that below the critical size there are factors that prevent black holes from swallowing gas and growing, in galaxies with a mass of more than ten million suns, the attraction is large enough to pull more and more material from the galaxy to the black hole at its center
From the right: Prof. Eli Waxman and Prof. Avishai Gal-Yam

A star dies, a particle is born

Is the origin of a particle that landed at the South Pole in a cosmic event 700 million years old?
A black hole photographed in polarized light, revealing its magnetic fields. The Event Horizon Telescope Partnership (EHT)

The magnetic field of a black hole was photographed for the first time

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The scientists observed the black hole in the center of the galaxy M87 that was photographed about three years ago by optical means, and now the huge magnetic field around it has been photographed which reveals what happens when matter approaches the speed of light and part of it is swallowed up by the black hole. The writer is one of the scientists who participated in the project
Colliding neutron stars can create solar-mass black holes. Credit: Robin Dinell / Carnegie Institution for Science

What is the connection between stellar black holes and dark matter?

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When LIGO and Virgo observe more black star collisions, they may observe many small black stars. If that happens, we may have to examine this idea of ​​darker matter more carefully
A wormhole - a tunnel between distant regions of the universe. Illustration: shutterstock

Physicists: The existence of (tiny) wormholes is possible

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Physicists from Germany are examining the theoretical possibility of the existence of tunnels in space-time, but only particles can pass through them, and they will immediately close
Image: The main image shows a close-up of a quasar and a jet, like the one actually in PJ352-52. In: X-ray data from the Chandra Space Telescope Credit: X-ray: NASA / CXO / JPL / T. Connor; Optical: Twin Observatory / NOIRLAB / NSF / AURA; Infrared: WM Observatory; Image: NASA / CXC / M. WEISS

A giant jet ejected from a black hole in the early universe

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A star is torn apart by a black hole and emits jets of gas and radiation. Image: NASA/JPL

Stars engulfed by a black hole release energy long after the process begins

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Dr. Asaf Haresh of the Hebrew University revealed a new and surprising phenomenon concerning the destruction of stars by black holes* so far no researcher has been able to prove that such flashes of radio radiation exist, a relatively long time after the destruction of the star. The research even proves the power of the event and the partial understanding of the scientific world on the subject. The research was published in Nature Astronomy
A black hole emits jets of particles. Image: depositphotos.com

For the first time, a neutrino particle has been detected that came to us from the vicinity of a supermassive black hole

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A group of international researchers, including from the Hebrew University and the Weizmann Institute, discovered the particle that arrived following an emission event that occurred in 2019

The black hole at the center of the Milky Way is slowly spinning, but what does that mean?

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The black hole at the center of the Milky Way is slowly spinning, but what does that mean?
Prof. Reinhart Genzel at the Parnell Observatory, part of the Southern European Observatory project in Chela. PR photo, ESO

Nobel laureate Reinhart Ganzel is a great friend of Israeli science

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Says Prof. Hagai Netzer from the School of Physics and Astronomy at Tel Aviv University who wrote dozens of joint articles with Ganzel
Star S2 orbiting the black hole at the center of the galaxy - Sagittarius (Sagittarius) *A, one of the proofs for the existence of the black hole at the center of the galaxy, from the research of 2020 Nobel Prize winners Reinhart Ganzel and Andrea Gas. From Wikipedia. By ESO/M. Kornmesser - https://www.eso.org/public/images/eso1825b/ , CC BY 1825, Link

"Without the observations of Ganzel and Gas, the whole subject of black holes would have remained theoretical"

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Illustration of the galaxy and the giant black hole at its center. The black hole converts some of the matter it absorbs into energetic radiation (shaded in blue), while the galaxy continues to form new stars (purple areas). [Image credit: Michael Helfenbein/Yale University - M. Helfenbein / Yale University]

Roger Penrose and the two black hole detectors at the center of the galaxy won the Nobel Prize in Physics

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Simulation of a gravitational wave event. Illustration: MIT-LIGO

The most massive gravitational waves ever

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A binary black hole merger probably created gravitational waves equal to the energy of eight suns * "Bang" in the Ligo and Virgo detectors is a signal for the source of the most massive gravitational waves ever
Left: The remnants of a rogue star ripped apart by the black hole crash onto the disk, while the hot region above it is still radiating X-rays. Right: The crashed star disrupted the gas disk, turning off the X-rays. Credit: Robert Hurt, NASA /JPL

What interrupted a supermassive black hole's feast?

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Researchers have identified a star that got too close to the "dinner table" and was swallowed up as well
Black holes collide in close proximity to a supermassive black hole. Image: CUNY

Astronomers find evidence of colliding black holes that emitted light

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