Well this week is Halloween so you have to be careful if you are out late at night trying to observe some deep space sky. So, while we spent some time partying, I also read more about solar system formation and the problem of angular momentum, so let's get into that topic first.
Recall from the previous post of October 26 where we talked about the importance of the "dead zone" and magnetic fields in the formation of planets. One issue hidden in that discussion was the so called "angular momentum problem" which always comes up when we consider the collapse of molecular clouds to form first of all starts and then as now planets
The angular momentum problem, really the issue of the conservation of angular momentum, comes about because as particles and gas of the original molecular cloud are drawn by gravitational attraction to the center of mass, the initial rotational velocity of any given mass of gas cannot continue falling directly, but must circulate and orbit around the center of mass, until it has lost enough energy to spiral closer and closer inward. But, the loss of angular momentum at one point in the cloud must be accompanied by an increase in angular momentum at another point in the cloud so that the conservation of angular momentum is still valid.
Ok, so the more I study the physics involved with this process, the more interesting the problem becomes. Now I am not convinced that there is actually a problem, called the angular momentum problem, but there is a need to explain how the collapsing gas cloud loses angular momentum, allowing the continuing collapse, and at the same time, transfers the angular momentum further out into the proto disk, in such a way as to maintain the conservation of angular momentum.
In searching for a good explanation of how angular momentum is transferred outward from the collapsing disk, I ran across this interesting book that is written as a dialog, in the same tone as the original Galileo dialog between the heliocentric and Copernicus theory of the solar system. But this time the dialog is between the predominately accepted "nebula theory" and the "capture theory" of solar system formation. The book by Michael Wolfson, see below, is according to the author's prologue, an honest dialog between the two theories while at the same time the author is a fierce advocate of the minority position.
A Dialog on the formation of the solar system (Source: Michael Woolfson)|
I was a bit worried about this book, again after reading the prologue, that it might be a bit "kranky" in that the author says that he is retired and does not have a research position anymore and cannot afford to do the astrophysical simulations to do the additional research to help confirm the capture theory. Hmm, there might be a bit of that here but the dialog so far has been very fair, even though most astrophysicists go with the nebula theory. Each theory over the years has had trouble predicting the observations and the gaps in the theories called for more study and research to find out how to update the theories.
First of all, the capture theory says that the better way of explaining the history and formation of solar systems is to start with the Sun in orbit with another protostar or at least passing in close proximity to a protostar or molecular cloud. In this passage, the Sun grabs and collects gas and dust to form the planets. Hmm, well many stars start off as binary pairs so why not consider some interaction of this type to be how planets form.
The final decision as to which theory is correct will depend on the astrophysical evidence and which theory best fits the observations. I had never heard of the capture theory before so I am just starting to enjoy the dialog and try to follow along on the evidence and reasons why one would pick and select one theory over the other one. I try to follow both sets of arguments but it gets hard. On both sides there is much time spent on arguing how the conservation of angular momentum principle applies to each case and how the forces in the collapsing or interacting clouds enable the coalescence of planets while at the same time transferring angular momentum from the inside core to further out in the clouds. Wow, this book is going to take a lot more work! It is also a good description about how science works by comparing and contrasting explanations and theories in order to get the best agreement between theory and observation. I'm also starting to see how various interactions between planets in their orbits and interactions with gas in its orbits and resonances between their orbits can give rise to exchanges in angular momentum such that the planet can migrate inwards or in other cases migrate outwards. In the exchange, the planet that gains in angular momentum will move outward and the planet that loses angular momentum will move inwards. Pretty neat stuff!
Well, my head was starting to hurt from wondering about angular momentum transfer in solar system formation and the operation of science that I retreated to the easy chair with a nice glass of port. This is where I also finalized my idea for a Halloween costume. Normally, I prefer Graham's tawny port, but the iconic image of Sandeman Winery, showing the outline of the "Portuguese university student", seemed to be a good costume approach. When we toured Sandeman winery in Porto, Portugal, their gift shop had the student cape and hat for sale, but I didn't select it then, but now would cobble together something like that for Halloween celebration.
When your head hurts from thinking about angular momentum; Drink Port! (Source: Sandeman Winery)|
So, here we are, I as the Portuguese student and Resident Astronomer Peggy, in a medieval velvet dress with bell sleeves, as we arrive at our community clubhouse for this year's Halloween party. I didn't quite achieve the student look that I was after, but we were ready to party! Maybe I should have tilted the hat down more like the marketing Icon for Sandeman!
Resident Astronomers arrive at the party receiving line (Source: Palmia Observatory)|
So we were having a lot of fun until a very charming and powerful person, who had just flown in, pulled up alongside Resident Astronomer Peggy. She was quite taken by the stranger, aka Pool Shark, Tony, and she seemed to fall under some sort of spell under his influence.
Resident Astronomer Peggy can't resist this nighttime visitor (Source: Palmia Observatory)|
Then, while all I could do was standby and watch, he bit Peggy on the neck. She was still under his spell and did not seem to mind the bite.
Finally, the creature, with blood still dripping from his mouth, retreated and left Peggy and I still stunned and not quite sure what had happened. When I could finally move, I could see two faint red marks on her neck, not quite puncture marks, but red marks nonetheless. So we tried to make the most of the event and settled in with more wine and snacks and dancing to mitigate any affects of the bite and strange encounter.
Resident Astronomer Peggy still stunned after bite (Source: Palmia Observatory)|
So, be warned, as you venture out, at this special time of the year, for star gazing or just old fashioned partying, stay clear of things that go bite in the dark. Hopefully, we will survive our encounter and get back to real night time observing soon!