The EHT, and M87's Black Hole:

[beecee]

https://phys.org/news/2021-03-astronomers-image-magnetic-fields-edge.html

Astronomers image magnetic fields at the edge of M87's black hole:

The Event Horizon Telescope (EHT) collaboration, which produced the first-ever image of a black hole, has today revealed a new view of the massive object at the center of the Messier 87 (M87) galaxy: How it looks in polarized light. This is the first time astronomers have been able to measure polarization, a signature of magnetic fields, this close to the edge of a black hole. The observations are key to explaining how the M87 galaxy, located 55 million light-years away, is able to launch energetic jets from its core.

"We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy," says Monika Moscibrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University in the Netherlands.

more at link.....

research paper:

https://www.eso.org/public/archives/releases/sciencepapers/eso2105/eso2105c.pdf

ABSTRACT:

We present the results from a full polarization study carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) during the first Very Long Baseline Interferometry (VLBI) campaign, which was conducted in Apr 2017 in the λ3 mm and λ1.3 mm bands, in concert with the Global mm-VLBI Array (GMVA) and the Event Horizon Telescope (EHT), respectively. We determine the polarization and Faraday properties of all VLBI targets, including Sgr A*, M87, and a dozen radioloud AGN, in the two bands at several epochs in a time window of ten days. We detect high linear polarization fractions (2–15%) and large rotation measures (RM > 103.3 − 105.5 rad m−2 ), confirming the trends of previous AGN studies at mm wavelengths. We find that blazars are more strongly polarized than other AGN in the sample, while exhibiting (on average) an order-of-magnitude lower RM values, consistent with the AGN viewing angle unification scheme. For Sgr A* we report a mean RM of (−4.2 ± 0.3) × 105 rad m−2 at 1.3 mm, consistent with measurements over the past decade, and, for the first time, a RM of (−2.1 ± 0.1) × 105 rad m−2 at 3 mm, suggesting that about half of the Faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. We also report the first unambiguous measurement of RM toward the M87 nucleus at mm wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year time-scale, spanning the range from –1.2 to 0.3 × 105 rad m−2 at 3 mm and –4.1 to 1.5 × 105 rad m−2 at 1.3 mm. Given this time variability, we argue that, unlike the case of Sgr A*, the RM in M87 does not provide an accurate estimate of the mass accretion rate onto the black hole. We put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the EHT (on horizon scales) and ALMA (which observes the combined emission from both components). These measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained VLBI data with the EHT and GMVA

 

[Area54]

I never fail to be amazed at the combination of theory and technology (and oustanding intellect) that leads to observations and discoveries such as this. It is a pity we often fail to bring the same commitment and focus to other problems, both global and personal. Thanks for the post.

[beecee]

55 minutes ago, Area54 said:

I never fail to be amazed at the combination of theory and technology (and oustanding intellect) that leads to observations and discoveries such as this. It is a pity we often fail to bring the same commitment and focus to other problems, both global and personal. Thanks for the post.

No probs! Your excellent reply sums it up beautifully.