Michael Gully-Santiago, PhD

astronomer, technologist

hello, most folks just call me gully

I am a scientist and technologist living in the San Francisco Bay Area. I work on the Kepler spacecraft, the most successful planet-finding telescope in history. My focus has centered on the ongoing K2 mission, which continues to revolutionize our understanding of starspots, supernovae, white dwarfs, stellar jitter, and more. I continue to develop and apply modular extensions to the statistical spectral inference framework Starfish. I used to lead metrology with the UT Austin Silicon Diffractive Optics Group, where I photolithographically patterned precise grooves on oversized silicon wafers the size of hockey pucks. During a NASA GSRP fellowship at the JPL Microdevices Lab I improved the precision of these devices even further. Recently I’ve become excited about scaling massive astronomical data analysis challenges with distributed systems and GPU-enabled inference frameworks.


igully [at] gmail [dot] com

NASA Ames Research Center
P. O. Box 1
M/S. 244-30
Moffett Field, CA. 94035-1000



Placing the spotted T Tauri star LkCa 4 on an HR diagram 2017
Michael Gully-Santiago, Gregory J. Herczeg, Ian Czekala, Garrett Somers, Konstantin Grankin, Kevin Covey, J.F Donati, Silvia Alencar, Gaitee Hussain, Benjamin Shappee, Greg Mace, Jae-Joon Lee, T. Holoien, Jessy Jose, Chun-Fan Liu
Astrophysical Journal, Accepted, 15 figures, 26 pages

Optical characterization of gaps in directly bonded Si compound optics using infrared spectroscopy 2016
Michael Gully-Santiago, Daniel T. Jaffe, Victor White
Applied Optics, accepted, 10 figures, 16 pages

High performance Si immersion gratings patterned with electron beam lithography 2014
Gully-Santiago, M.A; Jaffe, D.T.; Brooks, C.B.; Wilson, D.W.; and Muller, R.E.
Proc. SPIE

Near-infrared metrology of high-performance silicon immersion gratings 2012
Gully-Santiago, M.; Wang, W.; Deen, C.; and Jaffe, D.
Proc. SPIE

Confirmation and Characterization of Young Disk-Bearing Brown Dwarfs and sub-Brown Dwarfs 2011
Gully-Santiago, M. A., K. N. Allers, and D. T. Jaffe
Cool Stars 16

High-performance silicon grisms for 1.2-8.0 micron- detailed results from the JWST-NIRCam devices 2010
Gully-Santiago, M.; Wang, W.; Deen, C.; Kelly, D.; Greene, T. P.; Bacon, J.; Jaffe, D. T.
Proc. SPIE

The First SPIE software Hack Day 2014
S. Kendrew, C. Deen, N. Radziwill, S. Crawford, J. Gilbert, Gully-Santiago, M., and P. Kubanek
Proc. SPIE

New metrology techniques improve the production of silicon diffractive optics 2014
C. B. Brooks, Gully-Santiago, M., M. Grigas, and D. T. Jaffe
Proc. SPIE

Manufacturing of silicon immersion gratings for infrared spectrometers 2010
W. Wang, Gully-Santiago, M., C. Deen, D. J. Mar, and D. T. Jaffe
Proc. SPIE


Spectral inference of IGRINS data

IGRINS is a high resolution (R~40,000) spectrograph covering the entire H- and K- near-IR spectral windows in a single exposure. This immense spectral grasp presents both a new scientific competitive advantage, and an analysis challenge. I am leveraging a new statistical and computational approach that emulates synthetic spectra from pre-computed stellar model grid to compare with IGRINS data. The implementation of this approach, Starfish, is openly developed on GitHub, parallelized, and permissively licensed. The code provides an extensible modular framework for deriving intrinsic and extrinsic stellar properties. My work is centered around extending the code to model new astrophysical phenomena surrounding young stars.

Discovery and characterization of young brown dwarfs

Brown dwarfs are rare. The dearth of brown dwarfs is a manifestation of the stellar Initial Mass Function (IMF). Their rarity and the observational challenges of detecting them have conspired to yield small samples of brown dwarfs. Despite these limitations, brown dwarfs offer a unique astrophysical laboratory, to which we can ask the question “how do circumstellar disks change as a function of central object mass”. Or radiation environoment. Or gravitational potential. Etc. The agregate properties of young brown dwarfs can reveal how astrophysical processes govern star formation. For example, we’re learning about circumstellar disk dispersal timescales as a function of central object mass. These ideas ultimately inform our understanding of planetary habitability, and the diversity of stellar and planetary systems.

Silicon Immersion gratings

The Jaffe Silicon Diffractive Optics Group has been making diffraction gratings out of monocrystalline silicon. Silicon is an excellent optical material in the infrared because of its high (n = 3.4) refractive index, which shrinks Si immersed wavelength, and reduces the overall size of an infrared spectrograph design by a factor of about 3 to 10. Weisong Wang and I custom-made the Si immersion grating for IGRINS.

AstroML meetup and textbook figure hacking

Some of us were getting together to do examples from the AstroML textbook, “Statistics, Data Mining, and Machine Learning in Astronomy: A Practical Python Guide to the Analysis of Survey Data”. This book is the killer app for self-education in Machine Learning for Astronomy, and was (for better or worse) how I taught myself Python. The Python source code for every single figure in the book is online (we love you Jake). I hacked some of the textbook figures and posted them online too.

They Blinded Me with Science

I kickstarted a science podcast for the KVRX science radio show They Blinded Me With Science. I produced 30 original podcasts with > 3000 collective downloads and plays (and counting). The 30-minute show typically centered around researchers from the UT Austin College of Natural Sciences or beyond. Guests included Jeff Silverman, Rachael Livermore, Klaus Pontoppidan, and Chalence Safranek-Shrader, among others. All the podcasts are on iTunes!

Interactive Physics of Spectroscopy installation at UT Austin

I designed and installed this public outreach installation for the UT Austin Department of Astronomy. The exhibit is on the Astronomy Department’s 15th floor in Robert Lee Moore Hall. A large glass display case holds a hydrogen spectrum tube, Raspberry Pi micro-computer, web-camera, diffraction grating, and computer monitor. An arcade-style button triggers the Raspberry Pi to turn on the monitor, camera, and Hydrogen spectrum tube to show a live spectrum to any curious students or visitors passing by. The button gets clicked on average of 6 times per day.


Measuring fundamental properties of young stars November 18, 2016
Columbia University Stellar and Planetary lunch talk, NYC, USA

Forward Modeling IGRINS Spectra with Starfish November 12, 2015
High Resolution Spectroscopy with IGRINS Workshop, Seoul, South Korea

Data Science in Astronomy with Git and GitHub January 31, 2014
Grad Student Postdoc Seminar UT Austin Astronomy, Austin, TX

Ideas for Metrology of Silicon Diffractive Optics November 1, 2013
UT Austin Astronomy, Si Optics Group, Austin, TX

Zygo Interferometry of Echelle Gratings November 10, 2013
UT Austin Astronomy, Si Optics Group, Austin, TX

Direct bonded Silicon Optics November 11, 2013
UT Austin Astronomy, Si Optics Group, Austin, TX

SPIE 2012 Invited talk about Silicon Immersion Gratings July 6, 2012
SPIE Astronomical Telescopes and Instrumentation, Amsterdam, Netherlands

McDonald Observatory Board of Visitors Invited Public Talk February 11, 2011
UT Austin BOV meeting, ACES, Austin, TX