Mar 4 - The Gas that Fills Invisible Space

How do show something that's invisible? How can we view, model and understand those parts of our universe which are beyond the scope of our senses? How can we use a grad's students unwavering desire for pizza to explain our galaxies inexorable gas guzzling?

Yong Zheng took us on a journey from waking up and rifling through the fridge to building a massive galaxy by throwing swirling disks of stars and gas together. With delightful hand drawn cartoons and a many laughs she showed us that there's much more to the Milky Way than meets the eye, and by examining electromagnetic waves way out of the spectrum our eyes can see we can infer the private life of gas streaming in and out of galaxies. Culminating in beautiful films from the Illustris simulation she invited us to consider what interesting and varied information may be hidden just out of sight.

Afterwards Stephanie Douglas, gave a short talk on how clusters of stars passing near the milky way are ripped apart into long thin streams that we see cutting across the night's sky. Our 3D wall was showing off everything beautiful movies on topics ranging from the surface of our sun to collisions between galaxies. Patchy clouds and technical issues made observing tricky, but those who persevered were able to peer at the Orion Nebula and Jupiter using portable telescopes on campus. The roof was also open for tours but sadly conditions made it impossible to view the sky through it.  

-- Zephyr Penoyre (graduate student)

Feb 19 - Ripples in Spacetime

A record crowd packed into the lecture hall tonight to hear Jillian Bellovary talk about gravitational waves and how to detect them. Jillian's research focuses on supercomputer simulations of supermassive black hole binaries, but her presentation focused on much less massive binaries like those whose merger was detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in September. Gravitational waves are very small distortions in spacetime caused when massive objects are accelerated to high speeds. The distortions measured by LIGO were smaller than the radius of a proton -- and those were caused by two ~30 solar mass black holes merging together. Jillian showed simulations of how these ripples in spacetime are created by the two merging black holes.

Jillian also described how LIGO was able to detect these tiny distortions. LIGO is an interferometer, meaning it measures how light waves interfere with each other (either adding together or canceling each other out) after they travel a very long distance in two perpendicular directions. How the interference pattern changes with time tells LIGO scientists how the distance is changing in each direction. If the "arms" of the interferometer lengthen and compress in a particular pattern, then they know they've detected a gravitational wave!

The sky was cloudy, but graduate students Adrian Price-Whelan and Lauren Corlies, along with undergraduates Amanda Quirk and Cierra Coughlin, showed off the Rutherfurd Observatory. Meanwhile, undergraduates Richard Nederlander and Tze Goh screened short films on the 3D Wall. In the lecture hall, volunteers Stephanie Douglas, Maria Charisi, and Danielle Rowland played videos from PhD comics and from members of the LIGO team at CalTech, and answered audience questions about gravitational waves.

--Stephanie Douglas (graduate student)