Tag Archives: stream fanning

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


Stream fanning

streamfanning In my first year at Columbia I worked with grad student Sarah Pearson on an idea that Kathryn Johnston had while trying to find an orbit for Palomar 5 in a Law & Majewski potential. Wait what? Who’s Sarah, who’s Palomar 5, and what is a Law & Majewski potential?

Palomar 5 is a globular cluster in the halo of our Galaxy, the Milky Way. It is about 12 billion years old and consists of roughly 30,000 stars. The star cluster can be seen within the footprint of the Sloan Digital Sky Survey. But even more fascinating is that we can also see a stream, consisting of at least as many stars, stretching out from the cluster along its orbit. This stream – there are actually two, one in the leading direction and one in the trailing direction – spans about 23 degrees on the sky, while being on average half a degree wide. That’s about the size of 50 full moons!  Continue reading Stream fanning