Greetings from Palmia Observatory
Well, this week we find the sun has a big spot and we make some comments from the 52nd DDA meeting.But first, let's update our calendars to include the total lunar eclipse, visible here on the West Coast, for May 26, 4:18 am PDT. Maybe a diligent photographer will set an alarm and take some pictures for the rest of us. Also next week be sure to check out the Mars Innovation conference, held online, May 25 - 27.
|The sun woke up with a spot, DSLR, 300mm, ISO 200, 1/125 second (Source: Palmia Observatory)|
The AAS 52nd DDA meeting has concluded now and I am trying to summarize some of the findings discussed there. For now, my comment is on Carl Rodriguez's presentation on "Dynamical Formation of LGO's Binary Black Holes."
|Dynamical formation of black holes (Source: Carl Rodriguez, CMU @ 52nd DDA meeting)|
It turns out that studying globular clusters (GC) is a good place to look for the formation of black hole binaries. GC's are a good location to look for BH formation because of the way that GC's are supported by dynamic pressure from all of the stars that are bound together.
|Some binary black holes form in globular clusters (Source: C. Rodriguez, CMU @ 52nd DDA meeting)|
Any massive compact object that forms in a GC will move at its own peculiar motion, subject to the gravitational field generated by all the other stars. Other local or nearby stars will be attracted to the compact object resulting in higher stellar density behind the compact object.
|Mass segregation by dynamic friction (Source: C. Rodriguez, CMU @ 52nd DDA meeting)|
There will be many chaotic interactions between all of these stars and compact objects. Then due to conservation of angular momentum, these 3-body interactions can result in some objects being ejected from the GC, while often the binary system stays behind.
|Chaotic interactions can eject black holes (Source: C. Rodriguez, CMU @ 52nd DDA meeting)|
Radial velocity measurements of components of the globular clusters can identify black holes. Then various dynamic models can be compared with the measurements and the total number of black holes can be estimated.
|Black holes seen by radial velocity measurements (Source: C. Rodriguez, CMU @ 52nd DDA meeting)|
By observing multiple globular clusters, different estimates of the number of black holes and black hole binary systems can be evaluated. It turns out that the models show that GC's that go through core collapse, do so because many of the black holes are ejected from the GC. This ejection of black holes is what allows the GC to continue collapsing under the influence of gravity. Note that the models predict that when the GC has gone through core collapse that most of its black holes will be missing and have already been ejected.
|Counting black holes in globular clusters (Source: C. Rodriguez, CMU @ 52nd DDA meeting)|
Rodriguez summaries the data that shows about 1/4 of GCs that show core collapse have ejected all of their black holes.
|Core collapsed globular clusters eject their black holes (Source: C. Rodriguez, CMU @ 52nd DDA meeting)|
So these simulations and dynamic analysis showing the masses of the black holes that can be formed by these dynamic methods seem to indicate that all of the black hole mergers that were detected by LIGO could be formed this set of dynamical processes. Rodriquez poses the question but goes on to describe some of the missing pieces of the puzzle and how the data does not quite support this general conclusion.
|Black holes from GC's and LIGO mergers (Source: C. Rodriguez, CMU @ 52nd DDA meeting)|
LIGO also provides an estimate of the spin of the binary BH systems that are observed to collapse. The spin of black hole binaries is best explained as a result of the interaction arising in a globular cluster. The formation of the black hole binaries results in binaries with certain characteristic spin. So, the LIGO spin measurements provide another pillar in the argument that the black hole binaries were formed in globular clusters.
|LIGO spin measurements and dynamic formation (Source: C. Rodriguez, CMU @ 52nd DDA meeting)|
In summary, Rodriguez found that he dynamical formation of black hole binaries in globular clusters was the source of a major portion of those mergers detected by LIGO, but not the complete story. Other sources had to be included.
|But, there are other factors too (Source: C. Rodriguez, CMU @ 52nd DDA meeting)|
One of the most interesting aspects of Rodriquez's presentation was the connection between the spin of black hole binaries and how the binaries were formed. The spin of the binary system carries with it the history of its formation. Something about the spins can help identify where the system was formed. The chaotic history of dynamic interactions within globular clusters makes it mark on the spin orientation of the binary pair.
We might be able to further comment next time about the 52nd DDA meeting, but for now let's finish up with latest findings in our ongoing study of virology concerns the mechanism by which our bodies recognize that a given cell has been infected by a virus or other pathogen. One way it happens is from the natural degradation of viral RNA inside of each of the infected cells. The degradation of viral RNA is not any different from the normal degradation that goes on for various forms of messenger-RNA that each of our cells produce all the time. It turns out that the degraded viral RNA fragments are transported from the main cellular body, the cytosol, to the endoplasmic reticulum (ER). This transportation is very interesting in terms of physics because it does not rely on diffusion of molecules, but on active transport within the cell. There is a network of microtubules on which molecular motors actively carry and transport the selected molecules from the cytosol to the ER.
There is a normal molecular complex called the Major Histocompatibility Complex, or MHC, for short, in the ER that just waits to receive some portion of the degraded RNA protein, or normal degraded protein. When the protein segment enters the ER, the MHC binds to it and then by more active transport, the whole complex migrates to the cell surface. Once at the cell surface, the MHC enters the cell wall and displays the protein on the outside of the cell. This sets up the condition where this protein then interacts in a complex signaling pathway with other molecules and cells.
Now, with respect to SARS-CoviD-19, this displayed protein on the outside of our cells, interacts with other parts of our immune system which detects that this particular cell has been infected.
Our cells have many large molecules that take part in signaling what if going on inside a cell with the outside environment, all of which is necessary to support the ongoing complex cellular machinery of life. It is also due to one of these transmembrane molecules, the ACE2 receptor, that is necessary as a part of the blood pressure regulation system, that is commandeered by the virus as a way of entering the cell. So any anti-viral approach that interferes with ACE2 runs the risk of interfering with our blood pressure regulation system.
This whole process is illustrated in the following diagram that can be found in the textbook, "Immunology", by Kenneth Murphy.
|MHC molecules transport proteins to cell surface (Source: K. Murphy, "Immunology")|
This next screenshot is just the text block associated with the previous diagram.
| MHC molecules transport proteins to cell surface (Source: K. Murphy, "Immunology")|
If you are interested in more of the details of the microbiology of immune systems, I can recommend a good reference textbook. This book is quite technical but is clear enough for the armchair scientist to glean some of the intricacies and details. It has been quite helpful in gaining an understanding of some aspects of the public policy discussion on vaccination and also in gaining an understanding of the complex signaling and cellular machinery going on all the times inside each of us.
|Pretty good Immunology text book (Source: K. Murphy, "Immunology")|
Until next time, here from our burrow, stay safe, as we recover more of our freedom,
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