by Theodore R. Frimet
Observation and perception
There are regular and predictable motions of a galaxy’s spiral arm. On our carousel ride through our neck of cosmos, we typically move altogether. What perplexes me, the most, however, is the bumpy ride of the bar. Ask around. Maybe take a course, or two. Many have questions, and few of us, have answers.
I took an online Astronomy course, care of University of Arizona, a year or so back. One of the challenges was to subscribe, detect, and validate bar galaxies. I did so, by the dozens. It was fun, and fulfilling. Yet, all good things must come to an end. The experience did yield a future potential. It has given me visual insight as to what a bar galaxy should appear to be.
I have obsessed, or perhaps simply become more aware, of gravity waves. And their impact on clouds. Yes, back to Earth, for a little while. It is so wonderful to make first hand observations, just outside the door. I observe the cloud stratus with the apparent chaotic voids, separating the bands of white puffy moisture. The occasional updraft, at clouds end, shows the intent of a horizontal storm, a-brewing. Tilt it upright, and feel her natures fever. Yet beware! Toronadic forces abound in this child’s game of “name the cloud”.
Pull the horses hair bow across the violin string. Screech out a tone, or make music. It is all in the ear of the beholder. Is it not? Stars stretched out across our Milky Way arm, ride an intermittent gravity wave. Our brightly lit nebular masses bob up and down, up and down, for each encounter with a bar. They are the hair riding the string.
The bar, it is told to us, is a region of space that is tightly packed with stars. Yet, here I am, proffering that the star packed region has an immense gravity pool. Throughout these measurable perturbations lay a luxury of a commonplace comparison.
Draw the horses hair bow across the violin string. And vibrate the string. A very human endeavor. Now listen as our Cosmos draw the compacted stars across a region of space-time, where no sound may ever emanate. Exceptions abound, as in the LIGO experimenters transforming the blip of a detected gravity wave into our aural spectrum.
There is a difficult read for any beginner, looking for dynamic answers, here in the journal, Nature; “A dynamically young and perturbed Milky Way disk ” (1). I was hopeful that I would commiserate soon that a dwarf galaxy, or closed cluster, made its way to our doorstep. Perhaps it deformed our spiral arm. I was soon defeated, partly so, as the article makes no solid claims for either. They have used interpretations of the data, from the European Space Agency (ESA), Gaia, to infer our disk perturbations by the Sagittarius dwarf galaxy. This occurrence was between 300 and 900 million years ago. With another perturbation occurring about 2 Gyr, (giga-or billion years), ago.
More significantly, I learned that stars with similar velocities will stretch out in phase space, projecting as spirals. However, the article attests phase mixing in two dimensions. I steal at their thunder, when I suggest herein that the second dimension is the latent gravity pool, discarded by the solid mass of the Sagittarius dwarf. Yes, we are thick as thieves, now, as I continue to portend that gravity is as ever present as a dark cloud over your head.
What is the sound of the galactic wave? Is there no one here, to hear it? Does it make a sound? Of course it does! Ask any amateur. You just think you, “see it”.
Relax at the wide field of sight, and begin your journey with me. Now, go ahead. Feel it. You are in it. Yes, you and I are on the bob sled journey thru the fabric of space-time. Yield to her call and rediscover the gravity of the situation. Close one eye, my amateur, so that you do not loose your sight to the night.
(1) Antoja, T., Helmi, A., Romero-Gómez, M., Katz, D., Babusiaux, C., Drimmel, R., Evans, D., Figueras, F., Poggio, E., Reylé, C., Robin, A., Seabroke, G. and Soubiran, C. (2018). A dynamically young and perturbed Milky Way disk. Nature, 561(7723), pp.360-362.