Stephen S. Lawrence

Associate Professor of

Physics and Astronomy

Hofstra University

Department of Physics and Astronomy

151 Hofstra University

Hempstead, NY 11549

 

Office: CHPHB 102E

Voice: 516-463-5584

FAX: 516-463-3059

 

email username: Stephen.Lawrence

email domain name: @hofstra.edu

Research Interests

My research interests fall into three main categories.  Currently I am collaborating with Prof. Arlin Crotts and Dr. Ben Sugerman, on the light echo from Supernova 1987A.  Much as the flash of light from a shell in a fireworks display will light up the smoke from previous fireworks, the intense burst of light from SN 1987A is progressively illuminating clouds of dust in the nearby galaxy (the Large Magellanic Cloud, or LMC) that contained the supernova.  We are monitoring these light echoes in order to map the three-dimensional distribution of dust structures in the LMC, and also to determine the physical properties of LMC dust grains.  The image to the left shows a 10 arcminute field centered on SN 1987A (white spot at center).  The image is a PSF-matched difference image formed from subtraction of images taken in March 1995 and March 1996.  Only light sources that have changed across the year remain in the image, namely:  the supernova, bright saturated stars, variable stars and the light echoes.  The apparent superluminal motion of the echoes radially-outwards from the supernova leads them to resemble ripples in a pond.

 

 

I am also interested in the dynamics and evolution of supernova remnants, the shells of hot gas ejected by supernova explosions.  Prof. Crotts, Dr. Sugerman, and I are working with an international team to monitor the ongoing collision of the ejecta from SN 1987A with rings of circumstellar gas shed by the progenitor star thousands of years before it exploded.  The image on the computer monitor in my personal picture above shows the complex, three-ringed circumstellar nebula.  Click on the image at left to view an animation that shows the evolution of "hot spots" around the innermost ring as invisible debris from the fading  supernova at the center collides with the gas in the ring at titanic speeds.  I have also used Fabry-Perot imaging spectroscopy to construct three-dimensional models of the Crab Nebula and Cassiopeia A, two other relatively young supernova remnants.

 

 

I have also been working in collaboration with Dr. Patricia Knezek (WYIN/NOAO) and Dra. Irene Cruz-Gonzalez (UNAM) on an optical-IR catalog of massive low surface brightness disk galaxies.  These systems have total masses similar to normal high surface brightness galaxies, but have typically converted less than 10% of their gas into stars.  The images at right show a typical high surface brightness galaxy (left) and a low surface brightness galaxy of similar disk size (right).  A better understanding of these faint but massive systems can shed light on the mechanisms of galaxy formation and evolution and also on the nature of dark matter.

 

 

Another of my interests is the topic of astrobiology, or the search for extraterrestrial life.  I am particularly interested in the deposition of key elements from supernova into the interstellar medium and how this influences the “Galactic Habitable Zone” within our own Milky Way galaxy.  I am also interested in the true range of orbits that populate a habitable zone around a star of a particular mass, given recent advances in our understanding of stellar evolution, orbital evolution of giant planets, tidal heating, and the discovery of subsurface lifeforms that are completely independent of sunlight for survival.  The picture to the left shows a “black smoker” hydrothermal vent located at a mid-ocean ridge.  An entire ecosystem thrives near the 400 ˚C water spewing from the vent, with extremophile micro-organisms that feed on dissolved minerals and geothermal heat forming the base of the food chain.  This ecosystem thrives completely independent of sunlight!

 

 

 

Personal Info:

Education:

B.A. - Physics

University of Chicago

1988

M.S. - Astronomy

University of Michigan

1990

Ph.D. - Astronomy

University of Michigan

1994

 

 

 

 

Dissertation: Fabry-Perot Imaging Spectroscopy of the Crab Nebula, Cassiopeia A, and Nova GK Persei

 

Advisor: Prof. Gordon M. MacAlpine
Awarded the Ralph Baldwin Thesis Prize in Astronomy & Astrophysics


Experience:

2001 - present

Assistant Professor, Department of Physics and Astronomy, Hofstra University

2001 - present

Visiting Research Scientist, Columbia Astrophysics Laboratory, Columbia University

1998 - 2001

Postdoctoral Research Scientist, Columbia Astrophysics Laboratory, Columbia University

1997 - 1998

Visiting Assistant Professor, Department of Physics and Astronomy, Bowling Green State University

1995 - 1997

Resident Astronomer, Observatorio Astronomico Nacional, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico

1989 - 1994

Graduate Student Teaching Assistant, Department of Astronomy, The University of Michigan

1992

Lecturer, Department of Astronomy, The University of Michigan

1984 - 1986

Undergraduate Research Assistant, Department of Astronomy and Astrophysics, The University of Chicago

1985 - 1986

Teaching Assistant in Calculus, Department of Mathematics, The University of Chicago

 

Refereed Publications:

Full ADS abstract query for Stephen Lawrence

Work in Progress:

 

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Last updated: Jan 4, 2007