Friday, March 16, 2018

March 9 - Alien Weather

Our speaker this week was Statia Cook, a Columbia Teaching Fellow and a Research Associate at the American Museum of Natural History. She is an observational astrophysicist whose research focuses on studies of the weather and climate of other planets, especially the giant planets in the outer Solar System.

Statia started by orienting us to some of the key differences between weather on the Earth and on the "gas giants" (Jupiter and Saturn) and "ice giants" (Uranus and Neptune). On the Earth, the atmosphere is very thin compared the diameter of the planet -- similar to a few layers of cling wrap on a basketball. The giant planets, by contrast, are mostly (or entirely) atmosphere, although their density and temperatures vary with depth to such a degree that the same gasses may behave differently at different layers. In addition, the Earth's weather is driven almost entirely by energy from the Sun, whereas the giant planets still retain a large amount of heat from their formation. The release of that energy can be as important as the Sun to their climate. Finally, on Earth almost all clouds are water vapor, while the various colors seen in the giant planets trace clouds with different compositions including methane and ammonia.

Next, we heard about perhaps the best know extraterrestrial weather pattern: Jupiter' Great Red Spot, a persistent storm larger than the Earth that has existed for at least 180 and possibly more than 350 years. This vortex is accompanied by many other short-lived systems in Jupiter's atmosphere, with colors varying from white to pink to red. Neptune also had a giant storm, dubbed the Great Dark Spot, although it vanished in the five years between its discovery by the Voyager 2 spacecraft and observations by the Hubble Space Telescope five years later.

Finally, Statia told us about some of her own research which include detailed maps of Neptune using submillimeter radio interferometry, a pair of storms near Neptune's south pole that seemed to circle and merge together, amateur-inspired observations of a new Dark Spot on Neptune, and seasonal climate variation of the Ice Giants.

After the talk, Statia fielded questions, followed by a presentation by yours truly on the history of evidence for dark matter.

-- David Hendel (graduate student)

Sunday, February 25, 2018

February 23 - The LSST Revolution

Our speaker this week was Federica Bianco, a research scientist at both New York University's Center for Urban Science and Progress and their Center for Cosmology and Particle Physics. Her work focuses on transients - temporary changes in the sky. She is also the chair of the Large Synoptic Survey Telescope (LSST)'s Transients and Variable Stars Collaboration.

Federica's talk revolved around how the survey program of LSST will revolutionize our understanding of the changing universe, also known as time-domain astronomy. In particular, current studies tend to be at most two of wide (covering a large area of the sky), deep (observing faint objects) and fast (repeatedly observing the same place in quick succession). LSST is the first survey to attempt all three of these simultaneously by observing the entire Southern sky from its mountaintop in Chile, cataloging objects about 100 times fainter than current surveys with such a wide area, and imaging each patch of sky about once every three days -- with five different color filters.

LSST can achieve this due to its unique optical design that gives it an enormous field of view -- equal to the size of about 40 full moons -- and a 3,200 megapixel camera. This giant sensor will generate 15-20 terabytes of data a night, which will be immediately piped up to University of Illinois National Center for Supercomputing Applications in Urbana-Champaign, Illinois. There, the goal is to process each image and release in less than 60 seconds, including comparisons to previous data and generating an estimated 10 million science alerts per night. Just storing the 50-100 petabytes of data generated during its 10-year survey will be an immense challenge! Another amazing property of the LSST data is that it will be public immediately to all people in the US, so anyone interested can see what's happening in the sky almost in real time.

Federica also described the diverse science goals of LSST, which include understanding the nature of dark matter and characterization of dark energy; mapping the Milky Way; cataloging the Solar System; and exploring the changing sky. Many more details about LSST and its goals are available on its website.

After her talk, Federica answered questions in the lecture hall. Later, American Museum of Natural History fellow Betsy Hernandez gave a presentation on Active Galactic Nuclei while Columbia undergraduate Richard showed presentations on the 3D Wall and graduate students Daniel, Aleksey, and Adam gave tours of the observatory.

- David Hendel (graduate student)

Tuesday, February 20, 2018

Feb 9th - The Zoomable Universe

Our speaker this week was Caleb Sharf, a research scientist at Columbia University and Director of its Astrobiology Center. Caleb is a prolific writer with contributions in publications such as The New Yorker, The New York Times, The Atlantic, Wired, and Scientific American in addition to highly regarded scientific journals. He has also written a textbook on exoplanets and three popular science books on various astronomical topics.

In his talk Caleb gave an overview of his latest book, The Zoomable Universe. In it, he explores phenomena that cross the vast range of physical scales, from the very largest we can observe (the entire diameter of the observable Universe, about 10^27 meters) to the smallest (the Planck scale, 10^-35 meters, where the fabric of spacetime stops obeying known laws of physics).

Caleb uses this vast range - a factor of one hundred trillion trillion trillion trillion trillion, of which the human scale is conveniently close to the middle - to illustrate the incredible diversity of phenomenon in the Universe. Starting with the mysterious dark energy and the large scale structure of dark matter that makes up the skeleton of galaxy formation, we zoomed in repeatedly to examine the Local Group of galaxies, the birth of a solar system, the surface of a planet, and continued down to our own DNA and eventually the structure of spacetime. An illustrated version of this journey can be found here.

After his talk, Caleb fielded questions in the lecture hall while Columbia undergraduate Richard showed presentations on the 3D Wall while graduate students Steven and Aaron gave tours of the observatory. 

- David Hendel (graduate student)