Nov 21: Constellations R Us

This week, Irene Pease guided the audience through the constellations on the sky. Irene Pease has works as an astrophysics educator and leads astronomy classes as a Brooklyn’s Friendly Neighborhood Astronomer. During the lecture, Irene Pease showed us the distributions of constellations on the dark night sky in well-populated cities (e.g., New York) where city light has been a plague. Ancient sky across different cultures, such as Egyptian, European and Chinese, were compared, which amazingly showed great similarities in the definitions of constellations. She then introduced the modern constellations which were defined by Interactional Astronomical Union (IAU). The celestial sphere are divided into 88 official constellations, most of which inherit their names from their Graeco-Roman predecessors (e.g., Orion, Leo), while those in Southern sky have more modernized names (e.g., Microscopium). By using a ball and a cartoon paper to mimic the earth and horizon, Irene also explained the rotation of the celestial sky relative to the earth and the different paths of stars across the sky as viewed by observers at different latitudes. 

After the lecture, a video “The First Earth-sized World of Alpha Centrauri” was shown to the audience. This 7-minute long video introduced the first earth-sized planet orbiting around the star Alpha Centauri. On the roof, observations of double-star Alberio, open cluster Pleiades were led by graduate student, Jose Zorrilla. 

-- Yong Zheng (graduate student)

Nov 7: Juggling with Black Holes

This week, Hubble Postdoctoral Fellow Andreas Kupper described the dynamics of multiple massive objects in the same system.  When two massive objects are near each other, they exert gravitational forces on each other and their motions can be described analytically - that is, the motions at all times can be calculated by hand from basic theories.  When three or more massive objects interact gravitationally, the interactions become complicated and can only be modeled using computer simulations. Andreas showed the results of a few of his simulations - after the objects orbit chaotically around each other for a while, one object (usually the one with the lowest mass) is thrown out of the system with a very high velocity.  The remaining objects end up closer together, and this process, called scattering, is thought to be responsible for bringing massive objects like black holes and neutron stars close enough together that they can merge into an even more massive object. 

After the lecture, audiences were treated to a showing of LIGO: A Passion for Understanding, a 20 minute film about a project to detect gravitational waves coming from closely interacting massive objects.  After the film, graduate student Aleksey Generozov and I answered questions about gravitational waves and LIGO.   Graduate student Yong Zheng was the roof captain, sharing glimpses of the Moon, Albireo and the Ring Nebula while undergraduate Pratishta Yerakala took attendees on a 3D tour of the Universe with the 3D wall.

-- Steph Douglas (graduate student)

Oct 24: Stripping Stars

This week's Astronomy public lecture was given by post-doc fellow, Nick Stone, from Columbia Astronomy.  His talk "Stripping Stars: The Exciting Lives and Untimely Demise of Stars Near Supermassive Black Holes" led the audience to discover the dynamic processes associated with black holes.  Starting with an introduction to basic dynamics predicted by Newton's laws of motion and then general relativity, Nick familiarized the audience with the concepts of four dimension time-space and interactions between objects via gravity. Then he explained in detail the physics of black hole accretion, and broadened the case to dual-black hole interactions with the help of simulations. Finally, Nick showed what phenomena when we can expect to see as observers on Earth and how we can observe these energetic events in the Universe. 

About 150 people attended the lecture, after which they headed up to the Rutherfurd Observatory for to observe the Pleides open cluster and the spiral galaxy M31 (aka our nearest neighbor, Andromeda). Those who didn't go to the roof were treated to a slideshow on 'Gas Beyond the Milky Way Disk', by graduate student Yong Zheng, which introduced the very diffuse hot gas with more than 10 thousand degrees in the Milky Way potential well.

-- Yong Zheng (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) 

Sept 26: The Inconstant Moon

This week Columbia Astronomy's own outreach director, Summer Ash, discussed the many ways in which the Moon, frequently taken for granted in our night sky, can exhibit surprising and complex dynamics due to its complicated relationship with the Earth. After reminding us of the most well-known variation, lunar phase, she described the months - all six types!

Moving on from illumination effects, Summer described the many ways the orbit of the Moon around the Earth affects how we see it. Since its distance varies, sometimes it seems larger and brighter in the sky that others; this is the origin of the "Super Moon." Additionally, its orbit makes a small angle with the plane of the Earth-Sun orbit, which is why we don't experience eclipses at every new moon. Speaking of eclipses, she reminded us that total eclipses, where the moon completely enters the shadow of the Earth, are the ones you really want to get out of bed and check out. The Moon's red color during such an eclipse is due to the Sun's light being scattered by the Earth's atmosphere, the same reason the Sun looks red-orange at sunset: only red light can make it straight through!

If you were unable to attend the talk, or would like to read more, Summer wrote a blog piece on this same topic which you can read on Starts With a Bang.

After the lecture, graduate student Yong Zheng lead a lively discussion of the Milky Way's gas dynamics while Pratishta Yerakala demonstrated a variety of astronomical phenomena at the 3D wall and Adrian Price-Whelan, Jose Zorrilla, Emily Sandford, Maria Charisi, and Aleksey Generozov ran stargazing from Rutherfurd Observatory atop Pupin Hall. Objects targeted included the Ring Nebula, the Andromeda Galaxy, the Double Cluster and the beautiful visual binary star Albiero. 

-- David Hendel (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) 

March 7: Brain-gazing

This week we partnered with The Zuckerman Institute to help kick off Brain Awareness Week here in New York. This special event previewed a new visualization tool, Neurodome, designed to allow audiences to discover and explore the inner workings of the brain in a planetarium setting. The lecture was a blend of astronomy and neuroscience tracing the path of light through the Universe and into the brain. 

We started the evening with a fun quiz of "Space or Brain?" in which the audience had to guess if a given image was a picture of an object in space or a picture of part of the brain. Surprisingly most people were stumped at every turn! Next Matt Turk, a post-doc in the Department of Astronomy, spoke about how a particle of light, a photon, can travel from the farthest reaches of the observable universe and all the things that can happen to it along the way such as: reddening, scattering, absorption, and reemission. Matt left us and the light here on Earth and handed off the mic to Jonathan Fisher, a neuroscientist at New York Medical College. Jonathan and his colleagues then walked us through the various levels of the structure in the brain that the photon encounters and how Neurodome is allowing us to see the brain like never before. 

After the lecture, the audience was invited to tour to the rooftop observatories and further explore excerpts from Neurodome on our 3D Wall. 

We hope everyone enjoyed the interdisciplinary fun! 

-- Summer Ash (Director of Outreach)

February 21: Neutral Particle Power

Every second trillions of neutrinos cross our bodies without ever noticing. Graduate student Jia Liu guided the audience through the mysteries of these tiny particles that have puzzled scientists for decades. Neutrinos were suggested by the famous physicist Wolfgang Pauli to account for the missing energy, when a neutron splits into a proton and an electron (a process known as beta decay).

Neutrinos are abundant in nature and are produced through various processes. They are produced in the core of the stars when light nuclei merge to form heavier elements, in nuclear plants when the opposite process (heavier nuclei are divided into lighter) takes place to provide energy, in supernovae explosions and even when energetic particles from outer space interact with the atmosphere.

Neutrinos come in three varieties, have low mass and interact very weakly with matter, making their detection challenging. Next, Jia showed some of the cutting-edge operating detectors like IceCube in the South pole, ANTARES under the Mediterranean sea and Super-K in Japan, that trace neutrinos from astrophysical sources.

Finally, Jia discussed some intriguing potential (fiction-like) uses of neutrinos in the future, as proposed in serious scientific journals. Some of them included the destruction on nuclear weapons, the communication with extraterrestrial civilizations and equity trading.

After the lecture, the audience had the chance to view 3D movies of the universe on the 13th floor, to participate in roof tours and hear more about neutrino flavors from graduate student Andrew Weis. Later, as the sky cleared out and observing was possible, the few who stayed had the chance to look at Jupiter, the Orion Nebula as well as the new Supernova 2014J in nearby galaxy M82, which is the closest type-Ia supernova discovered in the past 42 years.

We hope to see you in our next event, which will entail an exciting collaboration with the neuroscience outreach group!

--Maria Charisi (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)