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)

Feb 13: New Developments in Gravity

It was a pleasure to have Dr. Rachel Rosen, Assistant Professor of Theoretical Physics at Columbia University, give a lecture on the New Developments in Gravity. Dr. Rosen is an expert in areas of research pertaining to field theory, cosmology, and particle physics. She is recognized for her contributions to the theory of massive gravity, a modified theory of gravity. In the lecture, she explained to us that the currently accepted standard theory of gravity is Albert Einstein’s general relativity. In this theory, the graviton (the particle responsible for the force of gravity) is a massless particle. However, Dr. Rosen stated that people have been interested in whether or not it's possible to modify this theory of gravity, particularly at large distances. One way to do this is to give the graviton a mass and make it a massive particle. Recently, it has been shown that it is possible to have theoretically consistent theories in which the graviton has a mass. The recent discovery of dark energy and the associated cosmological constant problem has prompted investigations for long distance modifications of general relativity. Dr. Rosen believes that making the graviton a massive particle may lead us to understand natural phenomena like the observed expansion of the universe.

After the main lecture, graduate student, Stephanie Douglas, gave a brief talk on star-forming regions in open clusters.  She showed images of open clusters such as Trumpler 16, Pleiades, Hyades, Alpha Persei, all ranging in age between 500,000 and 680 million years. Stephanie explained how some of the open clusters have regions that glow differently in different parts of the light spectrum (i.e., visible versus infrared).  She explained that when look at regions obscured by gas and dust in at different wavelengths we can pick out areas where stars are being formed.

After the lecture, audience members headed up to the roof to see the Moon, Jupiter, and the Orion Nebula. Graduate student, Adrian Price-Whelan, set up a digital SLR camera in the Big Dome to demonstrate how it's still possible to see faint sky objects, even from the heart of New York City. The image below was taken through our 14" Meade telescope.

-- David Jaimes (post-back student)

May 3: Why Dark Matter Matters

On Friday night, Kerstin Perez, a post-doc here at Columbia, told us that we can only see about 20% of the mass in the universe. The matter in the universe is mostly stuff that we can't see. The way that stars move in galaxies tells us that there's a lot more mass in those structures than we thought. But this extra mass doesn't emit light or interact with magnetic fields - we only see its gravitational effect. Because the matter doesn't emit or absorb light, astronomers have named it 'dark matter'. The current theory posits that dark matter is a fundamental particle that rarely interacts with normal matter, and then only via the weak nuclear force.

Kerstin also told us about the different ways scientists are looking for dark matter particles, including her own research. She built an instrument that flew on a balloon over Antarctica and attempted to detect the particles that form when two dark matter particles run into each other and annihilate. Other astrophysicists at Columbia are involved in a part of the ATLAS project at CERN that could detect dark matter particles from high energy collisions that simulate the early universe. Still others work at big underground detectors where they try to detect dark matter particles passing through Earth.

After Kerstin's talk, most of our audience members headed up to the roof of Pupin where Saturn and Arcturus were on display through our telescopes. The sky was clear and people were especially excited to check out Saturn's rings. A few folks chose to delay their observing to listen to a short presentation on the Herschel Space Observatory, the European Space Agency's infrared telescope which ran out of coolant last week and is no longer in operation. Others watched films about the universe on our 3D wall. 

--Steph Douglas (graduate student)

http://www.esa.int/Our_Activities/Space_Science/Herschel

February 15: My Life as a Higgs Boson

Friday, February 15th, Gladys Velez Caicedo had the very difficult task of explaining what exactly the Higgs Boson is and how its existence is necessitated by the Standard Model of Physics. The Standard Model explains all the particles we know, such as protons, neutrons, and electrons, along with their interactions. Gladys is a second year undergraduate at Barnard College studying Astrophysics and Literature and is a researcher at Nevis Laboratories working with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) and the Fermi Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope. If you missed the talk or if you just want to immerse yourself in some hard-core physics, you can view the slides from Gladys's talk here.

Over 175 people came out for the event, and we were lucky to have the roof available for star-gazing for an hour after the lecture despite the encroaching cloud cover. The 3D wall was manned by Bryan Terrazas.

After the lecture, I led a small discussion in which we talked about the recent meteorite impact in Russia, along with the near-Earth asteroid that came within 17,200 miles of us, closer than orbiting equatorial geosynchronous satellites! In comparison, the moon is between 220,000 to 250,000 miles away. The discussion was slightly free-form due to the recent nature of the event, and it included us watching some internet videos from Russia. The discussion also focused on efforts humans are undertaking to detect future near-Earth asteroids and possible collisions. Thanks to all who came and participated in this Friday’s outreach program!

Meteor and asteroid videos:
Russia Meteorite Compilation
Another Meteorite Video
Asteroid 2012 DA14 Close Approach
Asteroid Discoveries

--Emir Karamehmetoglu (undergraduate student)

December 2: Are there other Universes?

Last night we had a fantastic lecture given by postdoctoral researcher David Kagan entitled: "Is Our Universe Alone in the Multiverse?" David covered a full introduction to assure everyone was on the same page for this high-level but philosophically interesting subject. He described the idea of an expanding observable universe, the multiworlds interpretation of quantum mechanics, the inflaton field theory and how it could describe other universes popping into existence ourside of our observable window and more. After his talk, he fielded questions for the remainder of the period from a group of dedicated enthusiasts.

In addition to the lecture, we had great observing conditions on the roof. Adrian Price-Whelan led a crew of graduate volunteers on our telescopes, helping attendees see the Pleiades, the Andromeda Galaxy, the first-quarter Moon, and Jupiter. In addition Yuan Li ran the 3D visualization wall permitting attendess to see simulation results and education movies in 3 dimensional projections. Thanks to all of the 160 people we had turn out!

--Cameron