Friday, March 17, 2017

Mar 3 - Las Atmósferas Estelares

(This was our 3rd Annual Spanish-Language Lecture)

Turns out the Sun has an atmosphere, albeit very different from Earth’s. Alejandro Núñez, a graduate student at Columbia University, unveiled what is known about this gaseous envelope, layer by layer. He further described how a flotilla of space probes is helping scientists clarify some remaining mysteries by continuously gathering data from all angles and wavelengths. The most vexing of these unsolved questions is how the corona -the outer layer of the Sun’s atmosphere- can be hundreds of times hotter than the photosphere -its visible surface-, reaching temperatures in excess of a million degrees Celsius. While a detailed description of the heating mechanism still needs to be developed, it seems to be linked to the complex interaction between the Sun’s magnetic field and its atmospheric plasma.

Turns out the Sun is also a star. Thus, we can extrapolate what we learn about the Sun to other stars. As Alejandro explained, we need to do so with caution, for different stars can have diverse levels of magnetic activity. He illustrated this with a discussion on how the red dwarf at the core of the recently discovered multiple planetary system Trappist-1 seems to be much more active than our Sun, and the consequences that this could have for the habitability of the planets orbiting it.

This was the Spanish public lecture of this season, and the audience had the opportunity to stargaze at the Rutherford observatory on Pupin Laboratories’ roof after the talk. The night was cold and partly cloudy, but we managed to get a glimpse of some objects like the Moon and Mizar through some clearings.

-- Jose Zorilla (graduate student) 

Tuesday, February 7, 2017

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)

Wednesday, January 25, 2017

Dec 16 - How to Hold a Dead Star in Your Hand

Our speaker, Kimberly Arcand, didn't come from an astronomy background. She began her science career as a biologist studying deer ticks, then moved into computer science before joining the Chandra X-ray Center (CXC), where she is now the visualization lead. Her job is to take the data and turn it into interesting and useful pictures. The data is beamed down from the telescope to NASA and then sent to the CXC as a lot of 1s and 0s. This is cleaned and assembled into black and white images; part of Kimberly's job is to determine how best to color these images to make them informative. Often, Chandra images are colored by the X-ray energy range or the dominant chemical/element.

Color has meaning. Kimberly spends part of her time studying responses to different color schemes, and choosing the right color scheme based on the audience for an image. Scientists think of blue as hottest, but culturally most people associate red with heat. Because Chandra images are important for outreach to the general public, her team picked red for the hottest parts of an image, rather than the blue that the scientists wanted.

Kimberly also told us about her work on visualizing the Cassiopeia A supernova remnant. Chandra (along with the Spitzer infrared telescope and Hubble Space Telescope) has observed this expanding shell of gas over many years, and you can actually see the gas moving outward in images taken several years apart. There is enough data that her team could use software borrowed from brain imaging to make the first 3D model of a dead star. She showed us a movie where we flew through the Cas A remnant. They also made a 3D printed model of the remnant - you can download the free file here if you want to hold your own dead star in your hand.

After the lecture, undergraduate Richard took us on a tour through all the scales of our universe, undergraduate Briley showed short astronomy movies on the 13th floor, and graduate students Alex and Aleksey led tours of the roof. Myself and graduate student Moiya also helped facilitate in the lecture hall.

-- Stephanie Douglas (graduate student)