Episode 50: Mapping Our Galactic Neighborhood: Dark Matter, Galactic Collisions & Our Local Sheet

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The Star Spot Celebrates Episode 50

Today marks the 50th time I’ve welcomed you and our guests to the The Star Spot. It is also our two year anniversary. I wanted to thank each member of our great team of volunteers for getting us this far. We’ve had some amazing guests on the show. We hunted extraterrestrials with Jill Tarter and we built a universe from nothing with Lawrence Krauss. We explored saturn with Carolyn Porco and we chased comets with David Levy. We contemplated humanity’s future on Mars with Chris McKay and we searched for signs of life beyond the solar system with Sara Seager. We’ve talked with some truly fascinating people: astronomers, physicists, engineers, planetary scientists, philosophers, entrepreneurs, educators, historians, artists, activists, authors, journalists, and even a space travel agent! But the best has yet to come. So thank you for continuing to join us here at The Star Spot.

Feature Guest: Marshall McCall

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Today we’re joined by Marshall McCall for a special interview originally held in front of a live audience at an event hosted by the University of Toronto Astronomy and Space Exploration Society. A video excerpt from the event, featuring Professor McCall demonstrating the evolution of a galaxy, can be watched below

In front of a live audience, Professor McCall joins Justin Trottier for a wide ranging discussion on all things galaxies. McCall tells how he wound up as a gardener at the Dominion Astrophysical Observatory, briefly the largest telescope on Earth, and then off to the opposite corner of the world working at observatories in Australia. A debate with the audience ensues over northern versus southern skies.

The two then discuss whether our galaxy is unique, the importance of dwarf galaxies, and get controversial exploring alternative theories of gravity. McCall explains the role of dark matter in giving rise to the superstructure we see as cosmic webs of sheets, filaments and voids. If dark matter dominated our past, the Andromeda galaxy will dominate our future when, in 3 billion years, we collide.

The conversation concludes with a focus on McCall’s recent research on our mysterious local sheet of galaxies. Out to 20 million light years galaxies surrounding the Milky Way appear to lie on a surprisingly flat sheet. McCall describes this puzzling structure, which he dubbed the “council of giants,” and how work with his graduate student George Conidis is leading to startling revelations that suggest our neck of the woods might have some special qualities after all.

Current in Space

What effect does microgravity have on an astronaut’s internal organs? Ben gets to the heart of the matter. Then Anuj introduces us to an object called a Centaur which lives like an asteroid, behaves like a comet and has rings like a gas giant. And finally Dave shares the startling announcement of an equally puzzling new addition to our family, a dwarf planet in the inner Oort Cloud and the possibility that its discovery could point to a super-Earth far out beyond Pluto.

About our Guest

Marshall McCall is Chair of the Department of Physics and Astronomy at York University. After graduating with degrees from the University of Victoria and the University of Texas at Austin, McCall spent two years observing southern skies at Mt. Stromlo and Siding Spring Observatories in Australia. His research interests focus on the structure, evolution and formation of galaxies and galaxy aggregates. He was involved in recent discoveries of two hitherto unknown galaxies in the neighborhood of the milky way, research that is providing a new understanding of the puzzling arrangement of galaxies around our own.