Well I spent a better part of this week at the 230th meeting of the American Astronomical Society held in Austin, TX. The AAS is a professional astronomers society where the latest results and findings can be presented, discussed and critiqued. I have been attending this meeting for three years now and always have had a great time and learned a lot even if many of the more technical presentations are way over my head. My plan for this blog is to offer some brief takeaways from my perspective
as an amateur astronomer, and physicist wannabe, of the key points that made it into my awareness. My comments are not meant to be a thorough review and represent only those portions that resonated with me because of where I am on this journey through astronomy.
We were welcomed to the meeting by current AAS president, Christine Jones, who is an accomplished PhD astrophysicist at SAO and lecturer at Harvard. See photo below. The meeting had 3-4 plenary sessions per day, with the target audience being the general astronomers of diverse expertise, and shorter sessions more technical sessions designed for the experts in that particular field. These individual lectures could be something like 10-20 minutes long with time for questions. The topics covered the whole gamut of astronomy including astrophysics, laboratory verification of the physics and chemistry models used to explain observed astronomical findings, cosmology, star formation, formation and evolution of galaxies, solar physics, comets, asteroids, CMB, solar system dynamics and formation and evolution of planets and exo-planets, and probably a few other topics I have neglected to mention. I found most of the technical sessions mostly beyond my current interest or understanding, although I am getting the hang of it and am starting to understand what the main issues are, but the plenary sessions were very entertaining and educational.
|Waiting in the audience for President Christine Jones to welcome everyone to the 230th Meeting of the AAS|
Should amateur astronomers go to AAS meetings? Well, they are certainly welcome and the AAS just recently reduced the fee charged for non-members, from almost 150% above member rates to now the quite low just 50% of what is charged for professional members. That now is a pretty good deal. But, all attendees should recognize that there will be a lot of discussion of data and statistics and error bars and significance and random and systematic error and biases, etc., so if this is not your thing, you are forewarned. After all it is a scientific meeting. The poster sessions were filled with some of the latest research and many of the poster titles simply were not understandable to me. Sometime when no one else was stopping at a particular poster, and especially if I didn't understand the title at all, I would ask the presenter what it was all about and they were always eager to explain what their work was all about and I could start to understand what the title of the work was all about. For me, as a budding physicist wannabe and practicing amateur astronomer interested in doing some science type observations, its all great even if it is difficult and hard to understand at times, I do finally start to understand what the issue is that they are talking about. So now, my plan is just to present some of the key ideas I heard without going into a lot of technical details.
Plenary speaker, Katherine Freese, U of Michigan, author of "The Cosmic Cocktail: Three parts dark matter", and a Kavli Prize winner, spoke on "Looking for Dark Stars." Although she did not come out wearing her famous feather boa, her lecture was lively and full of interesting anecdotes of the personalities involved in her career. Her technical presentation covered the topic of dark stars, that is stars that are composed primarily of dark matter and that shine, not due to nuclear fusion, but due to the decay and annihilation of dark matter itself. She outlined how to search for these strange objects and verify that they are more than just the result of a theorists vivid imagination.
Rebekah Dawson, Penn State, and winner of the Annie Jump Canon Prize, made another of the plenary lectures. Recall that Annie Jump Canon was initially one of the "computers", working with the likes of Henrietta Leavit, working on the Draper Catalog at Harvard. Annie was eventually allowed to look through the telescope and in fact travelled to South America to observe the stars of the southern hemisphere. More of her and the other computers stories is well told in Dava Sobel's new book, "The Glass Universe" Anyway Dr. Dawson, was recognized for her work on using the inner solar system as a window on the origin of planetary systems. In fact her area of expertise was made a significant part of the AAS meeting with the studies of the inner solar system a major part of the number of presentations at the AAS meeting.
Catelin Casey, U of Texas - Austin, made a plenary presentation of "The Universes most extreme star-forming galaxies. Dr. Casey described the key importance of dust in star forming regions, even though dust is a minor component of the total mass of the galaxy. It seems that dust is very effective absorber of radiation and the re-emitting and scattering of the radiation that the dust stays a relative cool 50 K. These star forming regions are known as DSFG's (Dusty Star Forming Galaxies).
Bonnie Buratti, NASA, presented a summary of the Rosetta mission, which was primarily a European mission to orbit a comet, 67P and make a remote landing on the comet. Dr. Buratti described the dozen instruments on Rosetta and how the imaging and spectrometers were able to glean so much about structure and composition of the comet. Many organic molecules were detected on the surface and the detection of molecular nitrogen, N2, is considered definitive evidence that the comet had to form way out in the solar system because that is the only location that nitrogen would be found cold enough (about 30 K at distances > 40 AU) to form N2. There was discussion about whether the source of water on the earth was from comets. The scientific method is to look for evidence and one of the key approaches is to examine the isotope chemistry of earth water and compare it with isotope chemistry of water found on comets. It turns out that the water on comets does not match the isotope ratios found on earth so more study is needed.
Macarena Garcia Marin, ESA, made one of the several presentations concerning the effort going into planning the observations for James Webb Space Telescope (JWST), once it is launched. There are so many professional astronomers vying for time on the JWST that they hope to strengthen the hand of their proposed use of time by arguing that they have, though use of laboratory experiments or other techniques, concluded that they are using the minimum amount of observing time to establish their goals. For instance, they have done computer and laboratory experimentation and modeling to identify if they can meet their scientific goals with say just using two filters from the filter wheel rather than the other 6 or 8 filters from which to choose. A lot of work is ongoing how to plan for JWST observing so that the maximum amount of useful scientific data is gather in each observing session. The principal investigators can't just say hey, point there and observe for thousands of seconds without some well thought out observing plan based on evidence.
Swara Ravindranath, STSI. made another of the JWST observation planning lectures Dr. Swara described how the spectrometers on JWST worked and how the spectrometer is tied together with the imaging camera so that the observed spectra can be accurately identified with each target astrometry. She mentioned how the MIRI spectrometer can operate as a slit defined spectrometer and as a slit less spectrometer and the imaging camera in that mode can collect 1000's spectra per image. That is is pretty neat! As a budding amateur spectroscopy user, who is initially doing slit spectroscopy, where I collect only one spectra at a time, it is really neat how JWST can be configured to collect many spectra, even of lower spectral resolution, at one time. Again, so much effort is being put into pre-planning the JWST observational plan so that that highly valued resource is used most effectively. Included in this plan is to take many spectra at redshift z>7.
Chris Impey, U. of Arizona, and author of "Beyond our future in Space (2015)", presented an historical view of our species first efforts at getting into space and the exciting options just around the corner. He is a very dynamic speaker and I have attended many of his free courses on the internet formats offered by Coursera and Edx. He talked about how there is now a commercial spaceport in New Mexico, commercial space missions being planned and somewhat funded by billionaires, the useful concept of the space elevator, not in space around the Earth, but in orbit around the moon, as a very cost effective way of getting into deep space, and of how mining of asteroids could be a cost effective plan, and how terra forming of Mars is not a likely scenario anytime.
Konstantin Batygin, Caltech, presented the latest version of the ever popular "Planet 9 from Outer Space." This is probably the third version of this talk about planet 9 that I have seen in the last year, but Konstantin is a dynamic speaker and this time he went into more of the technical details and it made a lot more sense why the idea of planet 9, a planet of approximately 10 earth masses in a highly elliptical orbit, could very well be reality. For instance this time he presented six major reasons why the theory of planet 9 makes sense and some of reasons show that the theory does not just fit the existing facts of the solar system, but also predicted some things that were not part of the original data that now can be seen to be explained by the theory as well. This makes the theory very good and now all they must do is find the planet. Dynamic simulation, sometimes covering 1000;'s of orbits show that on occasion just a planets find themselves close together and these alignments result in resonances that can eject objects, change he objects eccentricity and inclination to the solar system disk. I didn't quite write down all six reasons and can only remember: that the first clue was the members of the Kuiper belt show unexpected clustering; The theory also predicts some high inclination objects which subsequently it was learned that these objects had already be observed. In addition the theory offers an explanation of why the sun' rotary axis is titled 9 degrees from the plan of the solar system and planet 9 could have tilted the whole solar system plane with respect to the sun. He says they have identified where to look for it and are busy trying to find it. It will be quite ironic if they do indeed find Planet 9, given that Konstantin's other co-investigator is none other than Mike Brown, Caltech, who also is the author of "How I killed Pluto and why it had it coming."
Manfred Schussler, Max Planck Institute, was the winner of the George Hale Prize and presented on our understanding of the solar magnetic field and how the theories over time went from complex to simple and now back to complex again. He talked about how the prizes' namesake was the first to discover sunspot magnetism and sunspot polarity rules. He described how it used to be that the sun's rotation was necessary for creating the magnetic field but that is now understand that rotation is not necessary and small scale magnetic fields are generated just by the turbulence of convective heat transfer cells. The sun's rotation does contribute to the dipole magnetic field and does distort the magnetic field lines created by turbulence. He said that magnetohydrodynamics modelling of the hot plasma has become so impressive that images of the simulated sun are so good that experts cannot tell which image is real observation and which is simulation. But he also explained that even though the surface features look great, it is easily known that the modern computer codes do not have enough resolution to be able to completely explain what is going on just below the surface. More work is necessary.
Jay Pasachoff, Williams College, spoke about some of the scientific measurements made during eclipses and presented some anecdotal comments about his journey to Patagonia to capture images of the February 2017 annular eclipse. Remember that an annular eclipse is one where the moon is just at the right distance that it does not completely occlude the sun during an eclipse and a bright annulus is completely visible even when the moon lies directly in front of the sun. He mentioned a fantastic website sponsored by the International Astronomical Union (IAU) and hosted by Williams College. The web page as been installed on the blog list of useful websites.
Also speaking about the eclipse seekers, there was also a screening of a new one-hour documentary that follows the life of two astrophysicists and how they got into astronomy with all of the hurdles and successes along the way and follows them as they teach their students and prepare for making solar eclipse measurements and like the rest of us, hope for clear weather. If you follow any of the astronomy and astrophysics videos on the science channel you will already be familiar with one of the astrophysicists, Dr. Hakeem Oluseyi. He told one anecdote about when he first attended college, he had no idea of what went on in college and his first class when the professor started lecturing and writing on the blackboard and all the other students sat quietly just kept writing in their notebooks. He grew up without any notion of college lecturing and his challenge was to overcome many obstacles to become an accomplished astrophysicist and now lecturer and professor. If you see this documentary in the news check it out!
|Poster at AAS meeting for the screening of this documentary|
Finally, I should mention that since the AAS meeting was held in downtown Austin, we were within easy walking distance of one of the Austin tourist attractions where bats have adapted to living under the Congress Avenue bridge and venture out in great flights of thousands of bats as the sun goes down. Well, I wandered the couple of blocks down to the bride and stood several folks deep along the length of this major bridge through Austin and also noticed the large collection of boats, canoes, paddle boat, surfboards and even large tourist boats that collect and all barge together on the river in front of the bridge, all for the chance to observe the flight of these darn bats just after sundown. Well the first time I was there, it was actually kind of impressive to see these thousands of blood sucking mammals, just boil out from under the bridge and fly off as a great swarm to begin their nightly feeding ritual. When I returned to the hotel, I called Resident Astronomer Peggy about what I had seen and she wanted to see the photograph of it since when she was last in Austin she had planned to visit the bridge but for some reason could not fit it into her schedule. Oh, oh, Well, I had not thought to take a picture because I didn't think I could get the bats to show up on my little IPhone. So after hearing her disappointment I resolved to go down to the bridge the next night. Well, as luck would have it, the bats were either on strike or off their feed and only one little swarm came out from under the bridge. Oh, oh, I failed again to get an image of the bats. There are many folks that look forward to sundown so that they can capture a photo of the bats, much like I suppose many of us astronomers who wait for the sun to go down so that we can get photos of stars and galaxies. Anyway, luckily I was able to make a little restitution to Resident Astronomer Peggy because I happened by chance while at the airport I was able to spy this little poster showing the bats swarming up into the air against the sky. Wow that is a great photo and poster thanks to the Austin Convention and Visitors Bureau!
|This poster sums up much better the experience of waiting for and seeing the bats|
So that is about it for this week. Later this week we plan to meet up at the OCA general meeting and then next week, I will be going to the SAS symposium in Ontario, California. If you want to see what neat things real dedicated amateur astronomers are doing you should come and check it out. Other than that since most of the university physics colloquia are entering summer break, I will probably just have a working lunch with the local physicist wannabes. The understanding of fundamental physics problem that I have been struggling with this week, especially after hearing it mentioned several times at the AAS meeting, is the Hanbury Brown (&) Twiss effect. This effect,first mentioned in this blog in a post of June 11, 2016, was used to measure, in 1956, the diameter of the star Sirius by measuring the correlation between photons received here on Earth from opposite edges of the star Sirius. This measurement is part of a wider topic called intensity interferometry which applies to classical radio astronomy as well as quantum mechanics applications. Why should photons from such large distances on a star be correlated with each other? Strange, even if that is what the mathematics says should happen!
Until next time,
Resident Astronomer George