Well, this week we are offsite at the American Astronomical Society 229th annual meeting in Grapevine, Tx. This is my third AAS meeting and I'm looking forward to the week and at the same time I think I will be really wiped out after trying to pay attention for that long. I don't have the same energy level, but at least they have some great barbeque here and great martinis and margaritas so all is well. Anyway, I wanted to summarize a couple of the plenary sessions I attended. I found
the plenary sessions much easier to understand and for some of the other technical sessions I found that oftentimes, even though I understood the words, I didn't understand much of any of the details.
As an aside, just walking from the hotel to the convention center, which by Texas standards was close by and connected with a covered walkway, I noticed the following sign announcing a gun policy that I had not seen before. See below.
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| Sign posted at entry to the AAS meeting |
Hey, we are in Texas and this sign really caught my attention. I guess the meeting planners are afraid of something? Maybe too many Texans? I don't know. There has been a history of events where discrimination and harassment occurred based on the early mostly male environment of professional astronomy. Vera Rubin, who recently just died, a great scientist and major discoverer of the effects of dark matter on galaxy rotation curves, was apparently one of many, who were harassed and discriminated against because they were women. As a result the AAS does a great job of being very inclusive and wants to include all people, women, minorities, LGBT persons of whatever background, which I certainly agree with. But, I hadn't noticed any previous gun violence.
On my previous business trips to Texas, my impression of Texans is pretty much summed up by the following photo of one of our refrigerator magnets. I kind of figured that there were lots of guns in
Texas and I usually felt pretty safe here.
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| One of my refrigerator magnets from attending many other business meetings in Texas |
Oh well, on to the meeting and I wanted to provide just a brief summary of some of the takeaway notes I took during the plenary sessions. I wish I had the actual presentations for review and clarification, but I hope these summaries will be useful for those who could not attend this meeting.
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| Inside the main ballroom at the AAS meeting |
The first plenary session was the Kavli Foundation Lecture given by William Bottke, from SWRI, on "Early Solar System Bombardment: Exploring the echoes of planetary migration and lost ice giants." Let me just summarize his talk as bullet points:
Planet formation requires gas drag
Pebbles feel the drag and slow down and become gravitationally bound
"NIce" model does a good job of predicting formation and instabilities in the system
Instabilities occur in the system over the course of 1000's of years
During their formation, planets can migrate and large Jupiter can cause the instabilities to throw
planets out of the solar system
"Nice" model works well with a 5th ice planet being thrown out
Model simulation pretty much matches our solar system formation
5th planet conjecture is mostly compatible with some sort of "Planet 9" formation
Heavy bombardment prediction can be investigated and verified by Martian Dichotomy
Heavy bombardment prediction can be investigated and verified by lunar near/far side differences in
crater formation
The GRAIL mission provided pivotal gravity data to evaluate crater formation and history
The second plenary session was the Annie Jump Canon award winner, Laura Lopez, Ohio State University, who spoke on "The Tumultuous Lives and Deaths of Stars." My summary of bullet points is:
Stars deposit energy/momentum on the interstellar medium (ISM)
Remote imaging can be used to determine pressure in the ISM and around the protostars
Feedback (from the impact stellar energy transferred to the ISM) removes gas from the center
Cloud gravitational collapse is key, but outflows and feedback modify the structure of the system
Star formation rate (SFR) is dynamical, but currently is 2 solar mass stars per year in the Milky Way
X-ray images from Chandra present good data on ISM heating from stellar outflows
Need more data. Waiting for future x-ray Surveyor (Lynx)
The third plenary session was the Russell Prize Lecture given by Christopher McGee, UC Berkeley. My bullet points for his presentation "How Stars Form" include:
Stars from as a result of interplay between gravitational and thermal energy
Energy injected into the ISM governs the evolution of galaxies
Normal stars and super novae inject energy and outflows
SFR depends on the level of turbulence in the galaxy
Need to show why typical stars are 0.2-0.3 solar mass
Look for universal principles and events
Need dark matter, but running out of room as to where and what dark matter is made of
Might need to consider alternative versions as to what dark matter is
Alternative dark matter theories, e.g. axions, don't generate the right star formation conditions
Astronomy is beginning to constrain the requirements for what dark matter can be
Magnetic fields, while important, do not seem to be strong enough to overcome gravity
Early, Population III stars, if they are still around now, would have to be less than 0-.8 solar mass
Ok, that is all I could make out of my notes. There was much more, but I couldn't follow it fast enough to write it down. Again, I would have liked to have copies of the presentations. I probably have missed major points and misinterpreted others, but, hey, if you want to get the real deal, its your job to show up at the next meeting! Like I mentioned in previous posts, I get caught up in trying to understand the units (e.g,. galaxies per megaparsec per Kelvin per centimeter squared per steradian, or some such thing) and I can't follow the rest of the discussion. Oh well, I just keep learning and trying. So that is it for this very long first day of the meeting.
Until next time
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