Current Projects

Computational Stellar Evolution

Computational Stellar Evolution focuses on the development of a two-dimensional computer models which predict the evolution of stars. These models will be used to study the effects of magnetic fields and rotation on the evolution of low mass stars. One application of these models is to study the lithium abundance in metal-poor stars to determine the primordial abundance of lithium, which is a key constraint on big bang nucleosynthesis. 


Fundamental Astronomy of Cataclysmic Binaries

In a cataclysmic binary, a more-or-less normal star orbits a white dwarf so closely that matter spills from the normal star onto the white dwarf. A rich variety of behaviors results -- nova explosions, dwarf nova outbursts, accretion disk precession, magnetic channeling of the accretion flows, and much more. The light grasp and instrumentation at MDM Observatory are well-suited to studies of these objects. For decades now, we have used these facilities to characterize the cataclysmic binary population, mostly measuring orbital periods through velocity spectroscopy -- a procedure that turns up a many interesting and unusual objects, more or less as a byproduct. We have also pioneered CCD parallax measurements of cataclysmics, and broadened that effort to other classes of nearby stars through several collaborations.

FACULTY CONTACT: John Thorstensen

The Most Extreme Starburst Galaxies in the Universe

We are part of a team that has discovered a population of extreme starburst galaxies with star formation densities millions of times higher than in our Milky Way. These galaxies are associated with winds being launched at thousands of km/s into the intergalactic medium, and appear to represent the most extreme possible conditions for star formation in the Universe. Our team is using a combination of optical, X-ray, and IR observations with Hubble, Chandra, Spitzer, and WISE, along with ground-based optical and microwave observations to better understand the nature of these enigmatic and important objects.


Searching for Intermediate-Mass Black Holes in Dwarf Starburst Galaxies

One idea for the formation of supermassive black holes is that they grew from lower-mass "seeds" that formed in the first generation of galaxies in the early Universe. In this scenario, some such seed black holes should remain today and provide a "fossil" record of the early cosmic formation of black holes. We are studying a candidate "intermediate-mass" black hole in a nearby dwarf starburst galaxy, using X-ray observations with the Chandra, XMM-Newton, and ASCA observatories, to help determine whether this object may indeed be a leftover "seed" black hole and explore the process by which it accretes material from the surrounding medium.


Ionized Nebulae in AGN: Cosmic Fluorescent Lamps Powered by Massive Black Holes

The luminous radiation from growing supermassive black holes (known as "active galactic nuclei" or "AGN") is effective at photoionizing the gas clouds in the host galaxy, producing huge ionized nebulae (or "narrow-line regions") glowing like fluorescent lamps that are thousands of light-years across. We are investigating the physical processes that form these nebulae, by measuring their physical sizes using optical spectroscopy from the Southern African Large Telescope (SALT) and MDM Observatory.


Exploring the Connection Between Galaxies and Their Central Black Holes

In the past decade it has become increasingly clear that the cosmic evolution of galaxies is linked to the growth of their central supermassive black holes, but the nature of this connection remains poorly understood. We are using various techniques, including groundbreaking far-infrared observations from the Herschel Space Observatory, to measure the rate at which galaxies form stars, and connect this to measures of black hole accretion from Chandra X-ray Observatory and Spitzer Space Telescope X-ray and mid-infrared observations as well as optical data, to explore whether stars and black holes grow from a common supply of cold gas, or whether the two processes have separate triggering mechanisms.


Uncovering Powerful Obscured Quasars

Quasars are among the most luminous and powerful objects in the Universe, powered by the accretion of matter onto supermassive black holes that reside at the centers of galaxies. While these amazing objects have been studied in depth since the 1960's, a large fraction of the quasar population has long been "missing", hidden by an obscuring screen of gas and dust. We are using powerful new infrared and X-ray observatories, in particular the Wide-Field Infrared Survey Explorer (WISE) and Nuclear Spectroscopic Telescope Array (NuSTAR), to peer through the dust and find these mysterious obscured quasars. We are investigating the abundance and spatial distribution of millions of obscured quasars detected by WISE and exploring the level of obscuration in these sources with NuSTAR, to determine the processes by which their are fueled and the large-scale cosmic structures in which they reside.


High Altitude Aerial Platforms for Astronomical Research

A telescope mounted on a lighter-than-air platform (balloon) at an altitude above 60,000 ft would be above all clouds and weather and would offer imaging quality nearly on par with spacecraft like the Hubble Space Telescope. We are part of a group of Caltech and JPL scientists and engineers investigating the possibility of building a high-altitude, long duration vehicle platform for atmospheric and astronomy that would offer a new, much lower-cost access to near-space conditions.


Distances to the Remnants of Recent Supernova Explosions in the Milky Way

Some types of stars end their lives in highly energetic explosions known as supernovae. Over the past 75 years, astronomers have discovered nearly three hundred remnants of supernovae in our Milky Way galaxy, and over a 1000 remnants in several neighboring galaxies. Many key properties of supernova remnants depend on knowing the remnant's distance from us, a quantity that is hard to accurately measure. Since distances to stars is relatively easy to determine with good precision, we have begun a research program that attempts to identify stars located inside these remnants in order to better determine their distances.