A Central Black Hole's Rotation Direction Doesn't Determine A Galaxy's Rotation Direction

While I didn't have strong expectations one way or the other, this paper's conclusion is potentially important to understanding galaxy formation, and tends to disfavor a purely accretion hypothesis. 

In contrast, the fairly strong correlation between central black hole size and galaxy size tends to argue for a very important role of central black holes in the galaxy formation process, because black holes only make up ca. 1% of a galaxy's mass.

The paper also makes notable observations about other aspects of spiral galaxy geometry.

We compare the apparent directions of rotation in the plane of the sky of active galactic nuclei (AGNs) and their host galaxies. The direction of rotation of the galaxy was inferred from the direction of the spiral arms, while the direction of rotation of the AGN was inferred from spectropolarimetry, where the change in relative polarization position angle (PA) across broad lines is believed to be caused by equatorial scattering. The numbers of co-rotating and counter-rotating AGNs are equal. 

Studies of the relative position angles of radio jets have implied that there is a "zone of avoidance" where jets avoid being in the plane of disk galaxies. We point out that bi-conical narrow-line-region outflows also avoid the plane of the host galaxy. 

The equal numbers of co-rotating and counter-rotating AGNs exclude the hypothesis that the "zone of avoidance" is due to a lack of large tilts of the black hole rotating axis relative to the host galaxy rotation axis. Our results imply that the relative orientations of spin axes are random, at least for the black hole mass range we consider. 

We propose that changes in the broad-line polarization PA with wavelength that do not closely follow the predictions of the simple equatorial scattering model are a consequence of the scattering dust being clumpy. We note a couple of cases of possible changes in PA over several years, which, if real, could be due to motions of the dust clumps or changing anisotropy of the continuum emission.

Loren Gigi, C. Martin Gaskell, "The direction of rotation of supermassive black holes is unrelated to the direction of rotation of the host galaxy" arXiv:2607.06902 (July 8, 2026).

Red River

Red River (Japanese: 天は赤い河のほとり, Hepburn: Sora wa Akai Kawa no Hotori; lit. 'The Sky Is on the Banks of the Red River'), also known as Anatolia Story, is a Japanese manga series written and illustrated by Chie Shinohara. The series was published by Shōgakukan in their Sho-Comi magazine from January 1995 to June 2002 and was collected in 28 tankōbon volumes. It is published in English in North America by Viz Media. An anime television series adaptation produced by Tatsunoko Production is set to premiere in July 2026. 

As of March 2019, the manga had over 20 million copies in circulation, making it one of the best-selling manga series. In 2001, Red River won the Shogakukan Manga Award for the shōjo category.

From Wikipedia.

The river after which the series was named, the "Kızılırmak (Turkish pronunciation: [kɯˈzɯɫɯɾmak], Turkish for "Red River"), historically known as the Halys River (Ancient Greek: Ἅλυς), is the longest river flowing entirely within Turkey.

I read this manga series when my children were in middle school, basically in the early twenty-tens, not long after I began this blog, as one of the first really epic manga series that I'd read. American comics and graphic novels have almost no sub-genre that approximates this series. 

It is back on my radar screen because the first episode of an anime based upon this manga series was released today, and so far, so good. It is a pretty faithful and successful adaptation so far.

Why am I writing about it here?

Because this manga series was instrumental in spurring my interest in prehistory, anthropology, and historical linguistics, in a story that brought the late Bronze Age Hittite Empire to life and contributed a lot to me caring about all of these fields. Some of my own writing on the Hittites can be found here.

And honestly, while it has fictional and magical elements, much like Bronze Age legendary history works actually written at or within a few centuries of that time period, by and large, this series has stood the test of time and is broadly consistent with what archaeologists, anthropologists, ancient historians, and historical linguistics scholars still believe now.

What all of those disciplines lack, however, that historical fiction like this can provide, is synthesis, relatability, and meaning. Academic scholars tend to focus in on tiny details and cower from providing a larger narrative or connecting the dots for fear of being wrong. But doing so takes away the joy and allure of that once captivated the people who are doing the work and keeps them motivated enough to continue to do so. Historical fiction can give the dry piecemeal reconstructions life and a "vibe" allowing you to feel some sense of what life was like back then.

The fictional account does so in ways big and small. For example, while the dialog is in Japanese (and translated into English in the versions I consume), this series retains enough of the historically accurate Hittite proper names to make those names relatable and not so intimidating, when you encounter them as you study the actual history of the Hittite people, a culture the remains the source of pivotal and important open questions in the broader picture of the Bronze Age and Indo-European linguistics.

Even the magical and supernatural and religious aspects of the story, while not actually things that happened in the past, are largely consistent with the religious and metaphysical worldviews of the people who lived in that era in Anatolia.

The Age Of The Universe

The Big Bang was about 13.6 billion years ago, although the uncertainty in that estimate is considerable since it is model dependent. This is consistent with both the age of the oldest stars inferred from their metal content, and the LambdaCDM model with a constant cosmological constant determined based upon cosmic background radiation. 

But if the Hubble constant had its low redshift value (which calls for a faster expansion of the Universe), the age of the Universe would be much shorter than that of the oldest stars in the Milky Way. 

Thus, you can't solve the Hubble tension by tweaking the model dependent cosmic background radiation based estimate of its value in a way that works. Either the Hubble constant isn't really constant, or there is something wrong with the low redshift estimates of its value which affect all of the methodologies for estimating the Hubble constant at low redshift even though they are independent of each other in their methodology (e.g. the Universe is not as homogeneous as we think and we are in an atypical part of it).

We estimate the age of the Universe using the Xiang & Rix sample of 247,103 Milky Way stars with high-resolution spectroscopy from LAMOST DR7 and Gaia eDR3 parallaxes. Stellar ages were estimated using YY isochrones up to 20 Gyr. To remove stars with unusually high and precise ages, we require old stars to be metal-poor and α-enriched. We also require consistency between YY ages and those obtained with FLAME based only on Gaia data. Our final sample of 155,600 stars within 5 kpc provides consistent cosmic age estimates using several techniques of increasing rigour. Our main results use an MCMC reconstruction of the latent age distribution, though our iterative reconstruction is very similar. 

Applying an innovative approach to our MCMC reconstruction and its uncertainties, we find that the oldest star has an age of A⋆ = 13.73 +0.18 −0.15 Gyr. Varying the quality cuts can at most reduce this to A⋆ = 13.31 +0.21 −0.18 Gyr or raise it to 14.02 +0.18 −0.15 Gyr using a much lower or higher age-dependent metallicity ceiling, respectively. Our inferred A⋆ is consistent with the 13.6 Gyr expected in CMB-calibrated ΛCDM, assuming the first long-lived stars formed when the Universe was 0.2 Gyr old. 

This agreement casts doubt on solutions to the Hubble tension solely through new physics prior to recombination, which generally imply a cosmic age of 12.9 ±0.2 Gyr to match low redshift probes. It is difficult for stellar modelling uncertainties to reconcile such a low age with our result given the low metallicities of the oldest stars in our sample and independent asteroseismic constraints.

Indranil Banik, Thenujaya Kudakolawa Kaluarachchige, Stephen Cookson, Harry Desmond, "The age of the Universe from a large sample of the oldest Galactic stars" arXiv:2607.00764 (July 1 2026) (Submitted to the Monthly Notices of the Royal Astronomical Society).