Tag Archives: talks

University of Virginia


Last week I visited Jennifer Sobeck and my former Yale-colleague Nitya Kallivayalil at the University of Virginia. Jen is the deputy project manager of APOGEE-2, which is a large spectroscopic survey collecting 300,000 high-resolution spectra of Milky Way stars (and other bright targets). Hence, her head is full of stellar atmospheres and element abundances. Nitya is the go-to person for proper motions of Galactic satellites, which is why there’s tons of overlap between my work and both of theirs. Frequently distracted by great food and stunning weather, we scienced around for a few days. Our brainstorming for low hanging fruits in the APOGEE-2 dataset brought us a few great ideas, which we will hopefully pursue within the next weeks and months. Steve Majewski, PI of APOGEE and also based at UVa, outsourced the same task to all his undergrads. Let’s see who’s first to have some results!

Hubble Fellows Symposium 2016


It was great to visit Baltimore one last time and see the other fellows again. Baltimore has become a major hub for astronomy, even more so since STScI started hiring for JWST and WFIRST. All my friends from Yale seem to live in Baltimore now!

Chaos in the Galaxy

N-body simulations of tidal streams formed by Galactic satellites on regular orbits (A & B), a weakly chaotic orbit (C), and a strongly chaotic (D). The orbits of the four satellites are quite similar in terms of eccentricity and apo/pericenters, but the resulting streams show (and amplify) the underlying chaos.

During Adrian Price-Whelan’s dissertation talk today at the winter meeting (AAS227) of the American Astronomical Society in Kissimmee, Florida,  I was reminded that I haven’t mentioned our publication here. Adrian went through a whole lot of effort and characterized regular and chaotic orbits in a typical galactic gravitational potential. Usually, orbits in such a potential can be broadly categorized into chaotic and non-chaotic orbits. Adrian looked at this distinction in terms of the streams that are formed by satellites on such orbits. Continue reading Chaos in the Galaxy

Hubble Fellows Symposium 2015

2015 Hubble_Fellows_Symposium_GroupPhoto 2

Right after getting back from Chile I headed straight to Baltimore for this year’s Hubble Fellows Symposium at the Space Telescope Science Institute. Every year most of the 51 Hubble fellows (three years with each 17 fellows) get together at these meetings to present their work to each other. It is quite a fun meeting, since you get exciting updates on nearly all major fields of astronomy within three days. Last year we criticized, though, that the schedule left no time for chatting, schmoozing and collaborating. This year the organizers relaxed the schedule  a bit, so every talk was only 20 minutes long. It made the meeting much more enjoyable and put the fun back into the symposium.

With the AAS in Seattle


The year 2015 started off with a trip to Seattle to attend the 225th meeting of the American Astronomical Society (AAS). I just became a member of the AAS (for which I’m grateful to my sponsors Kathryn Johnston and Jerry Ostriker!), and so this was the first time for me to attend one of these ginormous, annual meetings. When I first looked at the program, I was impressed (not to say overwhelmed) by the number of attendees, the variety of splinter meetings, and by the quality & quantity of career opportunities. This impression didn’t change much throughout the week.  Continue reading With the AAS in Seattle

Juggling with black holes


Last Friday I gave a public lecture on gravitational dynamics at the Columbia Astronomy Department Stargazing & Lecture Series. The talk was really well attended, and I was surprised to see so many people interested in hearing about astronomy on a Friday night. The big auditorium in Pupin Hall felt packed to me (my perception may have been biased, though).  Continue reading Juggling with black holes

Carne, Pisco and a Conference in Chile


With Steffen Mieske I’m currently organizing a conference called “Satellites and Streams in Santiago”, which will take place in April 2015 in Santiago de Chile. I’m very excited about this meeting, as the topic will be (as the name suggests) streams and satellites, and there hasn’t been a similar gathering of experts in these fields in more than a decade. With about 100 people, we will focus for one week on dwarf galaxies and globular clusters, which orbit around the Milky Way and nearby galaxies, as well as tidal streams, which these satellites produce while orbiting and dissolving in their host galaxy’s gravitational potential. Aim of the meeting is to bring the two communities together to create the big picture of how large galaxies like the Milky Way assemble mass over billions of years by eating smaller satellites and globular clusters, and how the gravitational fields of the host galaxies transform satellites with time.  Continue reading Carne, Pisco and a Conference in Chile