Oct 7 - Black Hole Duet

"We did it!" says the soundbite, and while the screen fills with fireworks the lecture hall fills with applause. This is the culmination of an almost century long journey between Einstein's first postulates of general relativity to our first detection of gravitational waves last September.

Maria Charisi, graduate student and guide through the fabric of space-time, took us through the last moments of the life of a binary black hole. The LIGO project has taken almost 50 years, from the first genesis of the theory to the eureka moment of detection, to find gravitational waves. By measuring the minuscule variations in space-time, a fraction of the width of the nucleus of an atom, we can observe the ripples from distant violent collisions between black holes. Since the first detection we've found 2.9 merger events (the last one we're only 90% certain of, the other results ring clearer than a bell) and when we restart it with improvements in a few years we might find as many as 50 more.

After the main lecture Jordan Borgman took us to Tatooine, Luke Skywalker's home planet to talk about how the planets of Star Wars match up with the exoplanets we're discovering in our galaxy. Meanwhile Erin Flowers guided us through 3D visualizations of the universe on all scales.

Up on the roof, Alex Teachey orchestrated a beautiful (mostly) clear night of viewing through the telescopes. In the able hands of Richard Nederlander, Aleksey Generozov and Rose Gibson we had telescopes pointing at Mars, the Moon, and the Double Cluster.

-- Zephyr Penoyre (graduate student)

Oct 2: The Glorious Past of Our Monster Black Hole

Last week, physics graduate student and NASA fellow, Shuo Zhang, introduced us to the monstrous black hole in the center of our galaxy. It is well established that every massive galaxy hosts a supermassive black hole in its center and Milky Way is not an exception. Astronomers analyzing the orbits of stars in the galactic center, enabled by advancements in observing technology, realized that the only feasible scenario for the dark object in the center is the galaxy is a black hole with mass of a few million times the mass of the sun.

The black hole is known as Sagittarius A-star (SgrA*), since it is located near the border of the constellations Sagittarius and Scorpius. Being the closest supermassive black hole we can observe, SgrA* is of great astronomical interest. But is it a typical black hole? SgrA*, is one of the quietest supermassive black holes among all the nearby galaxies. However, that wasn't always the case. Recently, the Fermi Gamma-ray Space Telescope discovered a bubble of gamma-rays surrounding our galaxy, which indicate that 2 million years ago, the black hole was very active, swallowing gas and expelling in at large distances. 

Shuo also mentioned her own work observing the black hole at the center of the galaxy with an X-ray telescope called NuSTAR (a NASA mission, in which Shuo's research group here at Columbia was a major contributor). Shuo observes sporadic X-ray flares, which last for a few seconds. During these flares the black hole becomes hundreds of times brighter and then returns to its quiet state. The origin of the flares is still unknown and it has been suggested that we observe the heated remnants of an asteroid that was ripped apart by SgrA*.

Unfortunately, the weather did not cooperate to allow stargazing. Whoever stayed after the lecture had a chance to see 3D movies of the galaxy lead by undergraduate student Richard Nederlander, or hear a short presentation by graduate student Emily Sanford, about the exciting discovery of water on the surface of Mars.

-- Maria Charisi (graduate student)

March 1: Martian Summer

We hosted author, Andrew Kessler, and approximately 80 members of the general public on Friday, March 1st to hear all about the people and the science behind NASA's Phoenix Mars mission. Kessler spent a year with the engineers and scientists who worked on Phoenix to learn what it takes to launch a spacecraft from Earth and safely place it on the surface of another planet. Phoenix landed near the north pole on Mars, the first craft to ever land in the polar regions of the red planet. It's mission was to study the history of water in the ice-rich boundary of the Martian arctic. To do this, the Phoenix lander was equipped with a robot arm that could scoop up soil samples for analysis by an array of instruments including a mass spectrometer, a wet chemistry lab, and a high resolution imager. Not only did Phoenix discover subsurface water ice, but it also found that Martian soil contained high concentrations of chloride which converts to perchlorate in the presence of sunlight. You can read all about the Phoenix mission and Kessler's experience in mission control in his book, "Martian Summer: Robot Arms, Cowboy Spacemen, and My 90 Days with the Phoenix Mars Mission" and you can follow him on Twitter here.

After the talk, audience members toured our rooftop observatory (with the help of graduate students Jennifer Weston and Yong Zheng and undergraduate Jose Montelongo), viewed 3D movies (with undergraduate Bryan Terrazas), and listened to graduate student Steph Douglas explain the myriad of motions experienced by the Earth from our rotation around the Sun all the way out to the expansion of the Universe.

Join us for our next event on Friday, March 15th when post-doc Ashely Pagnotta explains how supernovae are used to understand the mysterious force known as dark energy.

--Summer Ash (Director of Outreach)