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)

Sept 18: Hubble IMAX

The Hubble Space Telescope has been humanity's eye on the universe for over 25 years now. In honor of the observatory's birthday this year, last Friday we screened the IMAX film "Hubble" at Columbia. We were moved to a smaller room this year, but one of our biggest crowds ever came out to celebrate Hubble with us.

Hubble was launched in 1990, but was partly disabled until a 1993 servicing mission installed a contact lens (of sorts) that allowed Hubble to reach its full potential. Though the movie included clips from the launch and first servicing mission, it focused on the final shuttle mission to Hubble in 2009 (there were four servicing missions with five shuttle visits in total, not including launch). We watched as the astronauts, including now Columbia Engineering Professor Mike Massimino, persevered through technical and mechanical challenges to replace important instruments and stabilizing gyroscopes. These repairs enabled Hubble to continue its crucial role of observing our universe.

Another highlight of the film was the animated fly through of the iconic Hubble image of the Orion Nebula. The Hubble data on Orion is so detailed that scientists at the Space Telescope Science Institute and the National Center for Supercomputing Applications were able to reconstruct the Nebula in 3D. Although we couldn't show the 3D version, flying through the brightly colored nebula and zooming in to see the gaseous disks around infant stars took everyone's breath away.

After the movie, we showed a simulated clip of the Andromeda Galaxy colliding with our own (based on Hubble data), along with a cool solar system model built in the Black Rock Desert. On the roof, graduate student Steven Mohammed and four other volunteers who showed off the Andromeda Galaxy and the Ring Nebula. And when one of our 3D projectors on the 13th floor crashed, undergraduate Briley Lewis and grad student Zephyr Peyore thought fast and created a new presentation to educate visitors.

-- Stephanie Douglas (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)

Yeshiva University Outreach

On October 7 at 7:30 pm, about 30 students from the Chemistry Clubs at Yeshiva University visited the Astronomy Department to get a tour of the heavens. Graduate student, Jana Grcevic gave a presentation on color and chemistry of the heavens as well as a view of our 3D movie theater. Then, we proceeded up to the roof to get views of Jupiter, Alberio, and the Ring Nebula.