Recommended reading 

Recent post on astrobites.org about a paper led by a PhD student from our institute.

The Black Hole Tango: Kicks and Spins in Hierarchical Mergers

“The room is large and densely packed. As you twirl across the floor, someone extends their hand, inviting you to dance. The two of you spin around each other, the tension building with every step. As you draw closer and closer, you realize this isn’t a ballroom, and you’re not people. This is outer space, and you and your partner are black holes, spiraling toward one another in one of the most energetic events in the universe: a black hole merger. (…)”

https://astrobites.org/2025/04/07/gw_kicks_impact_bh_spins_in_hierarchical_mergers/

In light of that amazing view of the vicinity of Sagittarius A that's going around, I thought it might be topical to remind people of this magical visualisation from 2021:

https://www.youtube.com/watch?v=rQcKIN9vj3U

More info is available from NASA at:

https://www.nasa.gov/universe/new-nasa-visualization-probes-the-light-bending-dance-of-binary-black-holes/

Which includes a link to a page where it can be downloaded in any of several sizes using a "Download" link:

https://svs.gsfc.nasa.gov/13831

Black Holes May Be ‘Supermazes’ of Many-Dimensional Strings
—@SciAm

｢ Scientists would like an ultimate theory that can describe both the very tiny machinations of particles and the grand movements of galaxies. The insides of black holes, which are extremely small and extremely massive, are the ideal testing grounds for trying out such a theory ｣

https://www.scientificamerican.com/article/string-theorists-say-black-holes-are-multidimensional-string-supermazes/

"Sure, kid. That singularity you teased was naked as a jaybird. Whatever you say."

"It could have been! It could have been! I just know it!"

https://www.youtube.com/watch?v=vl6gzT1vK5k

On this day, six years ago, on 12 April 2019, both @LIGO instruments and the Virgo detector observed the gravitational-wave signal GW190412.

It was a signal like none before, because GW190412 was the first to come from two merging black holes with very different masses. Never-before-heard overtones in the frequencies of the gravitational-wave were observed. These also allowed a more precise determination of the properties of the two black holes.

https://www.aei.mpg.de/213678/a-signal-like-none-before

About a year later (on 20 April 2020), the paper with all the details of the discovery was published.

https://journals.aps.org/prd/abstract/10.1103/PhysRevD.102.043015 [Open Access]

In contrast to the popular idea of black holes constantly "gobbling up" matter, they can spend long periods of time in a dormant, inactive phase. But sometimes, they pop back to life. Such was the case with the black hole at the center of an unremarkable galaxy some 300 light-years away. The gravitational monster "suddenly lit up and recently began producing unprecedented flashes of X-ray light.” Read about it from phys.org:

https://flip.it/_0u79-

Supermassive #BlackHoles Could Strip #Stars Down to their #Helium Cores

https://www.universetoday.com/articles/supermassive-black-holes-could-strip-stars-down-to-their-helium-cores

String Theorists Say Black Holes Are Multidimensional String ‘Supermazes’ https://www.scientificamerican.com/article/string-theorists-say-black-holes-are-multidimensional-string-supermazes/ #stringtheory #physics #science #STEM #blackholes #astronomy

A distant galaxy is home to a ravenous supermassive black hole that appears to be playing with its food. Located over 12 million light-years from Earth, a spiral galaxy known as NGC 4945 is blowing powerful winds of material from the supermassive black hole located at its core. @LiveScience has more on this “messy eater.”

https://flip.it/b5q9OU

The Mysterious History of a Black Hole Has Been Decoded by Scientists : ScienceAlert…

One of the common misconceptions about black holes is that they devour not only matter, but also the history of that matter. So when a black hole forms, you can only guess how it came to be... #science #astronomy #blackholes

https://formuchdeliberation.wordpress.com/2025/04/05/the-mysterious-history-of-a-black-hole-has-been-decoded-by-scientists-sciencealert-2/

https://www.sciencealert.com/the-mysterious-history-of-a-black-hole-has-been-decoded-by-scientists

 New selected research highlight 

Towards a deeper understanding of black hole origins

Research team studies the impact of remnant kicks on spin distributions of black holes from hierarchical mergers

A new study revisits modelling of the spin distributions from hierarchical binary black hole mergers in dense stellar environments, such as globular clusters. It finds clear deviations from the unique spin distribution described in previous studies, and shows a way to identify black holes from repeated mergers, which could help shed light on black hole formation through precise spin measurements in future observing runs.

Read more https://www.aei.mpg.de/1244528/towards-a-deeper-understanding-of-black-hole-origins?c=26149

https://arxiv.org/abs/2503.21278

I suppose it is conceivable that a universe might be just matter flattening onto the surface of a rotating black hole, in which case, we might be the solution to the question of whether information is lost when it enters one. I wondered about that years ago. It would yield, I think, a spreading, but very flattened, universe. The universe would then tend to acquire the rotational velocity of the black hole, though not all at once. But I wonder why there wouldn't be a directional gravitational bias, if slight. It should be measurable.

If the above is ever proven true, Sabine will no doubt be pleased that there might be no free will.

It seems like, if you're a holographic universe replaying events of a past universe, then the whole darned universe got sucked into a black hole, not just a planet or two, and a black hole becomes a surface broadcasting holograms which look like what we see.

If that is the case, what can we say about smaller, local black holes? Are they replaying solar and planetary inputs? Where?

It would seem like, if there is replaying going on, it would be inside of the event horizon, although there is black hole radiation, so what do I know about that?

On the plus side, the information paradox would seem to disappear altogether. Yay, no paradox.

But then we are possibly living through the replaying of what happened to a doomed universe. Cheery.

And the passage of time is perhaps then underpinned by the rotation of a gargantuan black hole playing out a dead universe's data. Then local black holes should be altering the rate of the passage of time somewhat. Is the passage of time somehow coupled to the rotational rate of a gargantuan black hole, modified and localized by the presence of matter? Is its arrow fixed because of a gargantuan black hole's rotation? Hm. Could time have angular momentum?

I have officially reached peak coffee for today. Back to debugging misbehaving video game bots. Hey, if this is a black hole rerun, I've fixed them already. Woo-hoo!

Jets from powerful black holes can point astronomers toward where − and where not − to look for life in the universe

https://theconversation.com/jets-from-powerful-black-holes-can-point-astronomers-toward-where-and-where-not-to-look-for-life-in-the-universe-251560

> Whether a galactic environment has the right conditions for habitable planets to form could depend on how the black hole in that galaxy is rotating.

A nightly gravitational-wave candidate to start the week 

This morning at 1:35 UTC, both @LIGO detectors, together with Virgo, observed a possible new gravitational-wave signal.

If it is real, it came from the merger of two black holes. The luminosity distance is comparatively low at “just” 1.9 billion light-years.

The sky position could be determined – quite accurately – to about 27 square degrees (equivalen to 130 times the area of the full moon in the sky).

https://gracedb.ligo.org/superevents/S250331o/view/ [GraceDB]
https://gcn.nasa.gov/circulars?query=S250331o [related GCN Circulars]

#BlackHoles Could Help #Life Thrive, Not End It

https://scitechdaily.com/black-holes-could-help-life-thrive-not-end-it/

Friday gravitational-wave candidate 

This morning, both @LIGO instruments, together with Virgo, detected a new possible gravitational-wave signal (no. 202 in the current fourth observation run).

S250328ae – if real – came from the merger of two black holes at a (luminosity) distance of just 1.7 billion light-years. That's comparatively close.

The sky position could be determined very precisely to 14 square degrees (about 67 times the size of the full moon in the sky).

https://gracedb.ligo.org/superevents/S250328ae/view/ [GraceDB]
https://gcn.nasa.gov/circulars?query=S250328ae [related GCN Circulars]

Finding Clues in Ruins of Ancient Dead Star With NASA’s Chandra https://www.nasa.gov/image-article/finding-clues-in-ruins-of-ancient-dead-star-with-nasas-chandra/ #NASA #Astrophysics #BlackHoles #ChandraXRayObservatory #Galaxies #GalaxiesStarsBlackHoles #MarshallAstrophysics #MarshallSpaceFlightCenter #TheUniverse

New gravitational-wave candidate

Both @LIGO instruments, together with Virgo, have detected the 201st possible gravitational-wave signal in their current (fourth) joint observation run, O4.

S250326y came – if it is real – from the merger of two black holes at a luminosity distance of around 20 billion light-years.

https://gracedb.ligo.org/superevents/S250326y/view/ [GraceDB]
https://gcn.nasa.gov/circulars?query=S250326y [related GCN Circulars]

Postdoctoral positions in Computational Relativistic Astrophysics at our Potsdam institute

The “Computational Relativistic Astrophysics” department at the @mpi_grav in Potsdam led by Masaru Shibata announces the opening of postdoc appointments (2 years).

The department is currently composed of two group leaders, one senior scientist, and several postdoc researchers and students.

It focuses on several research topics in relativistic computational astrophysics including neutron star merger, collapsar, stellar core collapse and explosion, formation of supermassive black holes, and multi-messenger astronomy.

apply by 25 March 2025

https://www.aei.mpg.de/1227727/car-postdoc-2025