AP NEWS

Unveiling the Milky Way’s history with virtual labs

May 6, 2019

We’ve known for centuries that our sun is located in the stellar disk of the Milky Way, a typical spiral galaxy.

Galactic astronomy, however, entered a period of renaissance in 2013 thanks to the Gaia satellite and the Sloan Digital Sky Survey-IV, the latter partnered by UW-Madison.

These two space missions have mapped the stars in the stellar disk of the Milky Way.

New technologies adopted in these surveys are finally making a study of the structure of our galaxy possible.

For the first time in human history, we know the velocity and location for almost 2 billion stars in the Milky Way and we are discovering that many of those stars also host planets.

The Milky Way is the only galaxy where we can examine the structural details of a galactic disk of stars, which are widespread in the universe.

The oldest stars date from the Milky Way’s earliest history, and their spatial distributions reflect the physical processes that governed our galaxy’s formation.

From this, we can assemble a picture of the environment in which the stars in the old disk and the spheroid components of the galaxy formed, and how they were incorporated into the Milky Way.

My team and I are involved with two major research areas: high-resolution numerical studies of the structure and evolution of the Milky Way, and the ways in which dwarf satellite galaxies get cannibalized by the Milky Way, feeding a halo of stars surrounding the galaxy.

None of these phenomena can be created in a typical laboratory; instead, we have to create “virtual laboratories” on Earth to simulate the relevant physics with large-scale computational experiments.

We combine analytic models and numerical simulations that are leading to new insights into processes that form the stellar skeleton of our galaxy.

The art of computer modeling of our Milky Way has allowed us to make progress in addressing a long-standing question in astronomy: the origin of spiral arms in the disk of our Milky Way.

Using computer simulations of disk galaxies, our work in this field has shown for the first time that stellar spiral arms are not transient features – as was claimed for several decades – but rather they are self-perpetuating, persistent and long-lived.

In computer simulations of galaxy formation, the stellar halo of our Milky Way undergoes significant cannibalization of smaller companions during its lifetime.

The Sagittarius dwarf galaxy is one such small galaxy in the process of being drawn into the galactic stellar halo, and the spectacular tails of stars stripped by its gravitational interaction with the Milky Way have been visible and traced over much of the sky.

Progress on both the modeling and observing fronts is transforming the study of the Milky Way and the dwarf galaxies that surround it into powerful models that expand our understanding of galaxy formation.

The lessons and challenges learned from confronting observational experiments with computer simulations and analytic models are bound to have repercussions that will affect the entire field of physics and astronomy in the future.