Feb 3 - Earth in Human Hands

On Friday night, author and astrobiologist David Grinspoon shared his new book, "Earth in Human Hands", with us. He claimed we are entering a new era on earth called the Anthropocene - the age of humanity. For better or worse, we are reshaping our planet, and we have the capability to be aware of and intentional about the changes we enact. He also told us about another species living 2.5 billion years ago that caused catastrophic climate change: cyanobacteria learned to generate O2 through photosynthesis, which changed the composition of atmosphere and that destroyed many other bacteria that thrived on the previously methane-rich atmosphere. He also made the distinction between inadvertent vs intentional changes in climate. For example, when we began driving cars on a wide scale, we didn't initially understand the environmental impact that would have. However, in the 70s, the world responding to ozone depletion by banning chlorofluorocarbons (CFCs), intentionally working to recover that protective layer between the Sun and us. Finally, Dr Grinspoon believes we can positively affect future climate, even beyond reversing the effects of humans on the climate - we could avert a future ice age, for example, since we know those happen periodically even when the Earth is left to its own devices. 

After the lecture, Dr Grinspoon signed copies of his book, and then undergraduate Erin took the audience on a brief tour of the other planets in our solar system. Upstairs, undergraduates Richard and Cierra showed movies on the 3D wall, and graduate students Aleksey and Daniel led roof tours. 

-- Stephanie Douglas (graduate student)

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)

Dec 4 - On the Care and Feeding of Black Holes

Aleksey Generozov, a 4th year PhD student in the astronomy department, introduced us to the majesty of black holes. Black holes are regions in space-time, where gravity is so strong that nothing (particles or even light) can escape from inside; we could make a black hole if we squeezed the entire earth into the size of our fingernails.

Aleksey next described the discovery of a supermassive black hole at the center of our galaxy, the Milky Way. Observing the orbits of stars very close to the galactic center, with very high precision, astronomers concluded that an object very massive (with mass a few million times the mass of the sun) and very compact (that would fit in a sphere with radius smaller than the radius of our solar system) must be hidden in the galactic center. The only feasible explanation was a huge black hole. These days, we are actually on the verge of seeing the radius of the black hole (the event horizon), with a network of radio telescopes positioned around the globe.

And although the black hole at the center of our galaxy is relatively quiet, this is not the case for every galaxy. In the '60s, astronomers discovered some very bright radio sources, equally bright as some nearby stars, which they named quasars (quasi-stars). Later, when the size and distance of these objects were measured, it was realized that the enormous amount of energy is produced when gas falls onto a supermassive black holes at the center of a very distant galaxy. The gas is brought to the central black holes, when two galaxies collide. This also explains why our own supermassive black hole is quiet; It's starving! However, there is some evidence from observations of very high energy photons, that our own black hole had a more spectacular past. The talk concluded with Aleksey and the audience singing along "twinkle-twinkle quasi-star".

After the lecture, the audience had the chance to hear about the K2 mission, which is the second phase of NASA's Kepler space telescope, lead by graduate student Stephanie Douglas. Moreover, they had a chance to further explore galaxies and black holes by watching 3D movies, guided by undergraduate Briley Lewis. The clear sky and the mild temperature gave us a wonderful opportunity for stargazing on Pupin's roof with the help of Adrian Price-Whelan, Emily Stanford, Daniel De Felippis, Rasmi Elasmar, and Richard H Nederlander. Attendees were treated to views of the Andromeda Galaxy, the Pleiades star cluster, and the Red Giant Betelgeuse.

-- Maria Charisi (graduate student)

Oct 10: Explosive Lighthouses

This week, Columbia Astronomy's 4th year graduate student, Maria Charisi, gave a talk on gamma-ray bursts, or GRB for short. Gamma-rays are a kind of electromagnetic wave, like optical light, but with very short wavelengths, even shorter that of X-rays.

Maria started by telling us the history of how GRBs were discovered. The first GRBs were found by detectors which were built to detect nuclear explosion on the Earth during the Cold War. However, scientists found no correlation between these events and any nuclear explosions on the Earth. So this problem was passed assigned to astronomers to find out if they were related to any astronomical events. At first theorists proposed many mechanisms for GRBs, from neutron star collisions to alien space wars. Astronomers also argued about the location of these events. Some believed they were galactic; others believed they were cosmological. The varieties of theories and beliefs were due to the fact that the location distribution and distance of the GRB events were still unknown. With the launch of the Compton Gamma-Ray Observatory in the mid 90's and the Swift Gamma-Ray Burst Mission in the early 21st century, and with the red-shifts measured from spectra, astronomers finally concluded that GRBs are extremely luminous events that happen all over the Universe. 

Maria then described findings from more recent studies on GRBs. GRBs only last for a short time in the gamma-ray band, but astronomers believed there should be afterglows in other wavelengths, just like charcoals will glow as a fire burns out. They did follow-up observations of GRBs in the optical and infrared bands and found evidence of these afterglows. From the duration distribution of the bursts, astronomers split the GRBs into two different categories: short bursts which lasts less than 100 seconds, and long bursts which last a few hundreds seconds. 

The physical image of GRBs is still not clear today. One of the most widely believed theories is that when two compact objects collide, for example a neutron star and a black hole, tremendous energy is produced and ejected from two jets. If we happened to be in the line of sight of these jets, we would detect a GRB.

After the lecture, graduate student Jingjing Chen showed the first half of a PBS movie called 'Alien Planets Revealed' which discussed transit method of detecting exoplanets used by the Kepler mission. Unfortunately, the weather was not good for stargazing, so graduate students Jeff Andrews and Aleksey Generozov gave tours of the Rutherfurd Observatory instead while undergraduate Erin Flowers and post-doc Robyn Sanderson presented a variety of astronomical phenomena with the 3D wall. 

-- Jingjing Chen (graduate student) 

April 25: The Exoplanet Revolution

Less than ten years ago, astronomers only knew about a handful of planets orbiting stars besides our Sun, and all of those are nearby.  But the Kepler spacecraft has changed all that; Kepler scientist Lucianne Walkowicz told us how the telescope has revolutionized exoplanet studies.  Kepler spent 4 years staring at one specific patch of the sky, looking for planets around stars near and far.  Kepler exponentially increased the number of known exoplanets, and found many that are thousands of light years away.

Kepler searches for planets by watching for slight brightness changes caused by a planet traveling in front of its host star. This method easily detects large planets that are close to their host star, but Kepler has also found a bunch of smaller planets (between Earth-size and Neptune size) orbiting at larger distances. Although the larger planets are easier to find, it looks like planets a little bigger than Earth may actually be the most common type of planet in the galaxy! Lucianne told us that although Kepler's main mission has ended due to a mechanical failure, the telescope will likely keep operating in a new observing mode to search for exoplanets around even more stars.

Clouds prevented any roof activities, but volunteers Jennifer Weston and David Hendel provided tours of the observatory and volunteer Claire Ding showed movies on the 3D wall.  Volunteer Alejandro Nunez also gave a short presentation in the lecture hall about the electromagnetic spectrum.

-- Steph Douglas (graduate student) 

March 28: Our Hungry Black Hole

This Friday relaunched our lecture series after both spring break and daylight savings time so we now begin at 8pm.  Graduate student Yuan Li gave a lecture on an upcoming galactic event: the closet passing of a gas cloud (called G2) to the supermassive black hole in the center of our galaxy.  After explaining the basics of black holes, Yuan showed proof for the existence of our own, called Sagittarius A*.  She then explained that with our own supermassive black hole being so long dormant, watching the feeding of a black hole up close has implications for most areas of astrophysics.

(Almost) April showers kept us from observing on the roof but roof tours were still available along with our 3D wall.  David Jaimes also gave a presentation on the exoplanets discovered by the Kepler telescope, highlighting a number of resources available on the web for those at home.

Check out this New York Times interactive graphic on different planetary systems.You can toggle between orbital size and discovery as well as hover your mouse over the orbits for various information.

-- Lauren Corlies (graduate student) 

February 7: Five Billion Years of Solitude

We kicked off a new year of events with the help of local author, Lee Billings, who recently published his book Five Billion Years of Solitude on the search for life beyond our Solar System. The title actually refers to the expected "life span" of life on Earth and what we are going to do with our "moment in the Sun". Contrary to popular belief, life on Earth will end long before the Sun becomes a red giant (excluding anthropogenic factors) - in about 500 million years, in fact, when the carbon cycle comes to a grinding halt. Lee's talk focused on our efforts thus far to discover if we will spend our remaining time in the Universe alone. He presented up to date results from NASA's Kepler mission and discussed what exoplanet properties we can currently deduce from the data. For as much as we like to speculate about habitability, it turns out we are still a ways from being able to confidently tell if the ingredients for life are present yet. 

After the talk, audience members enjoyed the 3D wall run by undergraduates Varad and Claire, as well as an informal talk on gamma-ray bursts by Maria, a graduate student. Due to the harsh winter, only the Big Dome was open on the roof for observing and we instead brought our portable telescopes out on the plaza in front of Pupin for glimpses of Jupiter and the Moon. Thanks to Adrian, Emir, Jingjing, and Andrew for leading the stargazing charge. 

-- Summer Ash (Director of Outreach)

February 3: Top 11 Astronomy Stories of 2011

Last night, graduating grad student, Jana Grcevich, kicked off our Spring lecture series by recapping the "Top 11 Astronomy Stories of 2011." Some of the highlights included: the most massive galaxy cluster found, a possible detection of the Higgs boson, a possible detection of a supermassive black hole devouring a star, the 2011 Nobel Prize in Physics going to three astronomers, and the discovery of over 3000 new exoplanets.

Jana ranked the new planet discoveries as number one on her list and many people would agree. Understanding and determining the available real estate for life to grab a foothold in our galaxy, let alone the rest of the Universe, ranks as one of the top 3 questions asked by humanity since humanity could ponder its own existence. Jana explained how the discoveries were made, by the Kepler space telescope, by stating that it measures the dimming of light from a star to determine the nature of the object causing the dimming due to occultation (the object passing in front of the star). She then focused on some of the gems from this exciting database of planets which included the discovery of a super earth-massed planet (roughly 2.5x) orbiting around its star in the habitable zone - an object known as Kepler 22b. Afterwards, she pointed out some planets orbit around binary stars, giving a shout out to the fans of Star Wars who recall Tatooine’s planetary system. Last, but not least, she displayed the best determination for many planetary systems’ orbits and configurations which showed us that planetary systems similar to our own are actually common place and not rare as previous thought based on the planetary systems discovered before the Kepler mission.

Many good questions were asked from the 140+ attendees last night, proving that a recap of the LAST year’s exciting discoveries was a great way to start off THIS year’s lecture series.

--Duane