Sept 29 - Galactic Archeology

Our speaker this week was Keith Hawkins, a Simons Postdoctoral Fellow based in the astronomy department here at Columbia. Keith is a Galactic Archeologist. He searches for clues to the past of our galaxy, the Milky Way, similar to the way an archeologist seeks to learn about ancient civilizations and cultures. 

Keith started by telling us about the "fossils" he uses to study the galaxy - stars! Stars are fossils in two ways. First, at the great distances involved on the scale of the Milky Way, we see stars not how they are but rather how they were up to hundreds of thousands of years ago, before humans even evolved on the Earth. This is because light moves at finite speed and needs time to reach us from the distant galaxy. Second, many types of stars live for hundreds of millions or billions of years and so their composition provides clues to what was going on at the time when they formed.

Next we learned about the tools used in galactic archeology. We heard about the methods used to measure distances, chemistries, and velocities of stars: parallax and spectra. Keith demonstrated parallax by having the audience hold up a finger and close each eye in sequence; the finger appears to move relative to the background. This is analogous to how astronomers measure distances, except observations taken on opposite sides of the Earth's orbit, 6 months apart, replace winking. The amount the star appears to move relates to its distance from us. Spectra, obtained by splitting a star's light and measuring how bright it is at different colors, contain a wealth of information. Dark bands in the rainbow are often visible. These bands correspond to light being absorbed by different elements in the star's atmosphere, so examining their pattern can tell an astronomer which and how much of the elements are in the star. The specific chemical signature of a star can pinpoint its place of birth or prove association with other stars. The bands in the spectrum may also be shifted to redder or bluer colors than normal; the direction and amount of shift is due to the Doppler effect and indicates the velocity of the star relative to us.

Keith finished his talk by describing his research's goal: a complete map of the Galaxy containing information on the positions, motions, and chemical content of millions of stars. He believes this "chemical cartography" will be key to deciphering the history of the Milky Way. 

After the lecture and a lively question and answer session, undergraduate students Briley and Harrison showed 3D astronomy animations on the 13th floor while graduate students Steven, Aleksey and Haley pointed the Rutherford Observatory's telescopes at the Moon, Ring Nebula, and the double star system Albireo.  

-- David Hendel (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)

Feb 27: Neutron Stars

This past Friday, Slovko Bogdanov, a research scientist at Columbia University, gave a great talk telling us all about neutron stars. While stars are kept from gravitational collapse by the burning of their nuclear fuel, when this fuel source runs dry, look out! The resulting supernova can outshine the light from an entire galaxy. Neutron stars are the result of this process -- when a massive star collapses, the remainder is so compact that it can fit the mass of the Sun into a star the size of Manhattan. We looked at a number of supernova remnants and learned out about the discovery of fast spinning pulsars. We also learned about an event in December 2004 where a starquake in a magnetar (a highly magnetized neutron star with magnetic fields more than 100,000,000 times stronger than anything scientists can create) released a blast of gamma-radiation so strong that it had the same ionizing effect on our atmosphere that strong solar flares do -- but from a distance of 50,000 light years. Yikes!

Afterwards, Columbia Post-Bac David Jaimes gave a slideshow on the recent Rosetta Mission, where after 10 years, we successfully landed a probe on Comet 67P. He showed us some gorgeous close up images of the comet, and described some of the science behind this amazing feat of engineering. Others wandered to our 3D-wall, where we screened several different movies showing simulations of colliding galaxies and more. Up on the roof, the skies were clear and we had clear views of Jupiter, the moon, and the Orion Nebula with our Big and Little Dome telescopes.

-- Jennifer Weston (graduate student)

Jan 30: Cosmic Stretchmarks

Tonight Princeton post-doc, and cosmologist, Renee Hlozek explained what light can tell us about the early universe. She showed us this map of light from the early universe, called the Cosmic Microwave Background, which is almost entirely uniform - the temperature fluctuations shown are only a few parts per million. But such uniformity, along with the observation that the universe appears perfectly flat, was a problem for theories about the universe's beginning.  For the temperature fluctuations to be so small, every part of the universe must have been in contact at the beginning. Renee used the example of communication across the big lecture hall - if she asks the person in the front row what the favorite band is of the person in the back corner, the front row person won't know unless she has talked to the other person. 

So scientists came up with the theory of cosmic inflation, which explains the Cosmic Microwave Background very well. But Renee also told us that scientists don't want their theories to simply explain existing data - good theories also make testable predictions for future observations.  And inflation theories predict that we should see a particular type of polarization (the orientation of light rays as they reach our detectors) that isn't produced by any other object in the universe. So if we detect that type of polarization, called B-modes, then we have good evidence for inflation!

Many experiments are studying the Cosmic Microwave Background, and last year one of them announced that they had detected B-modes, but a leaked press release for tomorrow indicates that their supposed detection was probably due to interference from dust in our Galaxy. Renee told us that this is a product of good science - the scientific method involves checking your own and other people's work, to make sure results are accurate.  Renee works on a collaboration using the Atacama Cosmology Telescope, one of many experiments studying the Cosmic Microwave Background. She showed us a picture of the telescope, and also of four women who built one of its instruments. Another instrument currently being added to ACT will also look for B-mode polarization - it may still be out there!

After the main lecture, graduate student Andrea gave a short slideshow on a few asteroids and comets that have passed by Earth recently, and undergraduate Erin showed movies on the 3D Wall.  Graduate students Adrian, Jose, and Emily, along with undergraduate Rasmi, braved an extreme wind chill to let our attendees see Jupiter and the Moon from two dome telescopes on the roof. 

-- Steph Douglas (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) 

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)

September 13: Fossils of Formation

On Friday, September 13th, we launched our 2013 Fall Public Lecture & Stargazing series with a talk on the Milky Way. Post-doctoral researcher, Allyson Sheffield, presented what we currently know about the formation of our galaxy. It turns out that galaxies formed in a hierarchical manner after the Big Bang, with small clumps of gas and dust forming stars, then clusters of stars, and eventually protogalaxies and galaxies. In essence, all galaxies form by accreting other galaxies in a process called galactic cannibalism. Allyson's work deals with observing tidal streams surrounding our galaxy and tracing them back in time and space to determine what structures they originally came from. She is currently focusing her efforts on the Triangulum-Andromeda over-density.

After the lecture, many visitors headed to the roof for some clear sky observing of the Moon, Mizar and Alcor, Alberio, and the Ring Nebula while others remained in the lecture hall to hear about the recent news of the Voyager 1 probe entering interstellar space.

Friday's volunteers included graduate students Jinjing Chen in the lecture hall, Adrian Price-Whelen, Susan Clark, Steven Mohammed, Doug Thornhill, and Yuan Li on the roof, and undergraduates Gladys Velez-Caicedo and Varad Srinivasan on the 3D Wall.

Join us for our next event on Friday, Sept. 27th to hear more on Voyager 1!

--Summer Ash, Director of Outreach

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

March 15: Cosmic Candles

Last week, Ashley Pagnotta, a post-doc at the American Museum of Natural History, gave a talk entitled, "Supernovae: Cosmic Candles of the Universe." Ashely's research focuses on stellar explosions known as supernovae which occur toward the end of a star's life. Different phenomena give rise to different types of supernovae and by understanding the nature of these explosions, astronomers can better constrain the parameters that help us describe the behavior of our Universe. 

It was less than a hundred years ago that astronomers even discovered that the Universe wasn't static, i.e., "standing still". Using the doppler effect to measure the speed at which galaxies were moving away from Earth and cepheid variable stars to measure distance, Edwin Hubble made a plot of of these two variables and discovered that the farther a galaxy was from Earth, the faster it was moving a way from us. Today, we call this plot the Hubble Diagram in his honor and continue to update it as we make better and better measurements. You can make you own Hubble Diagram using data from the Sloan Digital Sky Survey here. 

While Hubble's work showed that Universe is expanding, it said nothing about the future of this expansion. To investigate this, two teams of astronomers proposed using Type 1a supernovae to probe the Universe out to greater distances, and therefore farther back in time. They used Type 1a supernovae instead of cepheid variables as these supernovae have a characteristic explosion that allows astronomers to use them as a standard candle of sorts; astronomers know how bright they are at a given distance so they can observe them at various distances and extrapolate their true distance based on their observed brightness. Both teams ended up discovering that the expansion of the Universe was *accelerating*, giving rise to the theory of dark energy, and as a result we awarded the Nobel Prize for Physics in 2011. 

Ashely went on to explain how studying how Type 1a supernovae form in more detail can help astronomers minimize errors associated with their distance measurements and thereby improve our understanding of dark energy. You can view the slides from Ashely's talk here. 

Unfortunately, the skies were cloudy again so after the lecture, the 120+ audience members toured the roof with the help of graduate student Adrian Price-Whelan, viewed 3D movies with undergraduate Jose Montelongo, and learned about Comet PANSTARRS with Director of Outreach, Summer Ash, and graduate student Yong Zheng. 

Please come see us on April 5th when graduate student, Ximena Fernandez, will present highlights from lesser known space telescopes that are providing astronomers with great glimpses of the Universe. 

--Summer Ash (Director of Outreach)

November 16: Living with the Stars

Dr. Helena Uthas's talk was of a different strain than most of our previous outreach events. She shared her experiences of the three years she spent as a support astronomer on the beautiful and isolated Spanish island of La Palma, off the coast of western Africa. It is one of the prime spots for astronomy in the world today, having the best “seeing” available on our little blue planet (seeing is how much the atmosphere perturbs the images of stars as seen through a telescope).

In this personal narrative, Dr. Uthas walked the audience of ~180 people through her time at the Swedish Solar Telescope (SST) and the Nordic Optical Telescope (NOT) and the life of an astronomer in such a remote location. We were shocked and impressed by the difficult loneliness that such a job requires, yet there also was a sense of lusting for the introspection afforded being in one of the most beautiful and untouched natural vistas in the world. After this captivating mix of science, nature, and self, the majority of the audience went up for observing. We had almost 200 people on the roof throughout the event, and our telescopes were pointed at the extremely bright Jupiter, along with the Pleiades star cluster and the Andromeda galaxy. Several people stayed in the lecture hall for a slideshow on galaxies. The evening wrapped up around 9 pm leaving attendees having played astronomer over the skyline of New York City and vicariously experiencing the life of an observational astronomer through Dr. Uthas.

 --Emir

March 16: Our Galactic Neighborhood

On March 16 at 8 pm, 190 visitors joined us in Pupin Hall to hear from Dr. Gurtina Besla, an expert in predicting the past and future trajectories of galaxies interacting with our own Milky Way galaxy with special emphasis on the Large and Small Magellanic Clouds. She showed us results from her research that have yet to be released indicating the exact manner in which the Andromeda Galaxy and the Triangulum Galaxy will interact and merge with our own galaxy eventually forming a new galaxy: "Milkomeda". Attendees were wowed by the ability for theoretical astrophysicists like Dr. Besla to predict the future of our galactic environment up to 8 billion years from now.

After the amazing lecture, visitors were treated to glimpses from our 3D Wall, a discussion of Astronomy Pictures of the Day, or a tour of our rooftop telescope facilities. Unfortunately, the clouds and haze prevented us from having a view of the heavens this week, but we cross our fingers for future Public Observing nights, the next one scheduled for March 30. Join us then!

--Josh

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