Last night's Secret Science Club by astrophysicist Charles Liu was another tour de force by an engaging, brilliant speaker. Dr Liu started his lecture with the bombastic declaration, "Pluto schmuto, planets I scoff at thee!" He was here to talk about galaxies and large-scale structures. Shortly afterward, he walked back his statement a bit, and said that he didn't scorn these little lumps of mud because, after all, he was a resident of one.
Dr Liu went on to describe the different forms of galaxies, with spiral galaxies having a high incidence of star, and elliptical galaxies having a lower incidence of star formation. The incidence of star formation may be inferred from the emission lines of a galaxy's spectrum (note the spikes on the graph of a spiral galaxy's emission line). There are also a minority of irregular galaxies, many of them being found billions of light years away (because of the distances involved, the images of these objects are ancient).
A brief overview of the supermassive black holes followed, accompanied by diagrams of the torus-shaped accumulation of matter around the black hole, and the flares or jets of excess material ejected from the accretion. This prompted an a cappella rendition of a song set to the tune of
Black holes, they don't suck, they don't suck, they don't suh-uh-uh-uck
But if you fall in one, then there's your new home.
Dr Liu showed a gallery of interacting galaxies, and gave an overview of the "collisions which occur between galaxies- he noted that the Milky Way is approaching the Andromeda Galaxy, but advised the audience not to change their retirement plans. He followed up the gallery of images with an overview of the procedures used by astrophysicists, giving a brief history of the Hubble and Spitzer (insert your own joke) space telescopes, and gave a plug for the Galaxy Zoo project.
The talk was a "grand slam", hitting the perfect notes as far as "sense of wonder" was concerned. Dr Liu's enthusiasm for the material was infectious, and he was a charismatic stage presence. He entertained questions from the audience, the best one concerning the reconciliation of the time differences between objects vastly distant from each other. While not his particular area of inquiry, there are differential equations that can be used to model the probably current relation between objects to create an image of the "superstructures" composed of galaxies.
I apologize for not giving a better condensed version of the talk... a lot of Six Points were consumed.