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Yale Astronomy


Colby Jurgenson headed the optical design process; his genius and DNA shine through in the clever design of EXPRES. He partnered with mechanical engineers, Gary Muller and Fernando Satoro of ASTRO EME, to dot every "i" and cross every "t," allowing the instrument to come together seamlessly on schedule. Colby also designed and built VUES, a white-pupil design spectrograph for Vilnius University in Lithuania, and an infrared spectrograph that was recently commissioned at Caltech's Palomar Observatory. Colby likes the Broncos and hates nightstands.

Tyler McCracken designed the front-end module to guide light from the telescope to EXPRES. His system runs at 600 hz to funnel all of the light from the telescope into an optical fiber. To understand the scope of this challenge, consider that the telescope mirror has a diameter of 14 feet, approximately the height of a single-story house; the optical fiber has the diameter of a single hair. Additionally, Tyler’s background in interferometer aided our work with the laser comb for EXPRES. Tyler is from Texas and still says “y’all” a lot.

Andy Szymkowiak has a genius that cuts across engineering, electronics, and programming for EXPRES. He is our resident expert for the laser frequency comb and all of the motor systems. He writes software modules to interface with motor systems for effortless, focused observing with EXPRES. Not just our go-to rocket scientist, Andy also serves as the group’s very own front page of the internet.

David Sawyer was our amazing systems engineer. You can count yourself lucky if you meet one “Dave” in a lifetime. Selfless and brilliant, Dave made the entire team function efficiently. Among his endless tasks, he designed and built the calibration system, organized the team, and kept track of the budget. You know Dave is a man to listen to when, despite living miles away, he walks into a meeting on a snowy day with a bike helmet.

John Michael Brewer is a postdoctoral fellow at Yale and the software architect for EXPRES manager. John Michael constructed the synapses of code behind an elegant GUI with the capability to track and record every detail of an observation. In his spare time, John has analyzed the spectra of thousands of stars to forge ground-breaking connections between the spectroscopic properties of stars and their orbiting planets as well as help disentangle noise sources in EXPRES spectra. John Michael Brewer would make the most amazing ice cream, and it is our hope that putting this on the internet will make him start up again.

Allen Davis is a Yale astronomy graduate student working with Professors Jessi Cisewski, Debra Fischer, and Eric Ford on one of the most difficult challenges the field faces: once we have the high precision data provided by EXPRES, how can we disentangle velocities originating on the surface of the star from orbital velocities incurred by a planet? Allen’s seminal work demonstrates how this should be possible. He is now developing a new optimal extraction code and is beginning a search for planets orbiting solar-type stars. Allen will understand your star trek reference for sure, just try him.

Ryan Blackman is a Yale astronomy graduate student involved with the construction and commissioning of EXPRES. He designed and built an exposure meter for tracking the flux-weighted centroid of observations, which will more exactly correct for the velocity of the Earth. After the departure of Colby, Tyler, and Dave, Ryan bravely stepped up and took the lead on completing the optical alignment of the spectrograph and finishing the commissioning of EXPRES. If you think Ryan Blackman is the type of person who regularly surfs, you are exactly right.

Ryan Petersburg is a Yale physics graduate student working on fiber scrambling for EXPRES. Along with Professor Hong Tang in applied physics and Professor Debra Fischer in astronomy, Ryan is pursuing the holy grail: a 14 GHz photonic crystal comb that spans UV, optical, and IR wavelengths all at once. If he is successful, this will be a game-changer for EXPRES and for the entire field of spectroscopic exoplanet surveys. Ryan’s considerable talents span both scientific and musical instrumentation.

Lily Zhao is a Yale astronomy graduate student working on the complex data-taking interface for EXPRES alongside John. Lily learned half a dozen different programming languages to translate the activities of different EXPRES subcomponents. Her first paper constrained the types of planets that might still be orbiting the alpha Centauri stars, our nearest neighbors. She is starting a search for low-mass planets orbiting low-mass K and M stars. Lily is the EXPRES blog czar; please tell her about every typo.

Joel Ong is a Yale astronomy graduate student who has simulated how calibration with a laser frequency comb will generate additional error from correlated pixel positions for high-precision spectrographs. He is now working with Professor Bijan Nemati (UAH), Dr. Mike Shao (JPL), and Professor Fischer to analyze the interferometrically measured pixel positions of EXPRES. With Ryan Petersburg and Dr. Adam Bolton (NOAO), Joel is also developing a spectral perfectionism code that will make our data, well, perfect. Joel has forgotten more about cooking than most people will ever know.

Christopher Leet is a Yale undergraduate majoring in computer science and astrophysics who has cracked a potential show-stopper for ground based observing. He has programmed a “Leet Tellurometer” that uses data science to exploit correlations that reveal micro-telluric lines, which arise from the Earth’s atmosphere. These tellurics raster across stellar absorption lines, producing particularly dangerous systematic and time-correlated noise. He’ll graduate in May 2018; then, watch out world.

Yonatan Zeff is a Yale undergraduate majoring in physics and astronomy who will demonstrate the accuracy of EXPRES data as part of his senior thesis project. He is developing the code to fit the signal from multiple planets. We are hoping for clear skies during his observing run in March so that he can graduate in May…just kidding, Yonatan.

Abby Mintz is a Yale undergraduate who is writing programs to fit Keplerian models to the precision radial velocities we will measure with EXPRES this summer. Abby will help with observing in Flagstaff, Arizona and will integrate new statistical methods into her codes.

Jessi Cisewski is a professor in the statistics department at Yale. With statistics students, Parker Holzer and Xin Xu, she is applying data science methods in new ways to solve statistical problems in astronomy. Her work with Debra Fischer, Eric Ford (Penn State University), Xavier Dumusque (Geneva Observatory), and Sally Dodson Robinson (University of Delaware) attacks the big challenge that stands between EXPRES and the detection of 100 Earths: velocities from the photosphere of the host star.

Debra Fischer is a professor in the Yale astronomy department. She has discovered hundreds of exoplanets and brings 20+ years of experience as the Principal Investigator for three spectrographs. She is a community co-chair for the NASA study on a Large Ultraviolet/Optical/Infrared space telescope. EXPRES is her dream machine, made possible by this dream team and the amazing astronomy department at Yale University.

Sally Dodson-Robinson is a professor in the University of Delaware physics department. Her work ranges from the theoretical study of planet formation to the statistical analysis of chromospheric activity in stars. Sally and her students are helping to distangle velocities that arise in the photosphere of stars from orbital velocities that arise from planets.

Lars Buchhave is a professor at the Technical University of Denmark (DTU) with the Danish National Space Institute. He and his postdoctoral fellow, René Tronsgaard Rasmussen are working to optimize the analysis of data obtained with EXPRES.

Gregory Henry is a senior research associate at Tennessee State University heading the Automated Astronomy Group there. He has been instrumental in providing photometric observations of EXPRES target stars, which gives an independent observation of stellar activity and can be used to determine stellar rotation periods through Gaussian Process regression.

Steve Girvin was the Deputy Provost for research at Yale who provided the support that allowed this project to flourish.

Pieter van Dokkum was the astronomy department chair through most of the building of EXPRES - he deserves at minimum a million thanks.

Gábor Fűrész is an instrument builder at MIT who served as a sounding board during the optical design process and throughout the project.

Andy Szentgyorgyi is an instrument builder at Harvard University who provided helpful guidance, especially in the early days of the project.

Francesco Pepe from Geneva Observatory led the construction of HARPS and ESPRESSO. He is our competition, but when there were problems near the end of commissioning EXPRES, he didn’t hesitate to offer a helping hand.

Matteo Genoni, Giorgio Pariani, and Marco Riva are extraordinary optical engineers with the Brera Astronomical Observatory who worked on ESPRESSO. In February, Matteo and Giorgio traveled from Italy and spent 10 long days with EXPRES, studying the optical design, running simulations, and helping with the final alignment.

The Lowell Observatory Staff, every one of whom went the extra mile. Frank Cornelius and Ben Hardesty are engineers at the DCT who helped with the installation and cheerfully supported the project when we had to take the two 1,500-pound vacuum chamber walls off, then on, then off... and finally on again.

EXPRES Cast and Crew

  • Professors
    • Debra Fischer, Astronomy
    • Jessi Cisewski, Statistics
  • Research Scientists
    • Colby Jurgenson
    • Tyler McCracken
    • David Sawyer
    • Andrew Szymkowiak
  • Postdoctoral Associates and Fellows
    • John Michael Brewer
  • Graduate Students
    • Allen Davis
    • Ryan Blackman
    • Ryan Petersburg
    • Lily Zhao
    • Joel Ong
  • Undergraduate Students
    • Christopher Leet
    • Yonatan Zeff
    • Abby Mintz
  • Collaborators
    • Sally Dodson-Robinson, University of Delaware
    • Lars Buchhave, Danish National Space Institute
    • Gregory Henry, Tennessee State University
  • We Would Like to Expressly Thank
    • Steve Girvin, Yale University
    • Pieter van Dokkum, Yale University
    • Gábor Fűrész, MIT
    • Andy Szentgyorgyi, Harvard
    • Francesco Pepe, Geneva Observatory
    • Matteo Genoni, Brera Astronomical Observatory
    • Giorgio Pariani, Brera Astronomical Observatory
    • Marco Riva, Brera Astronomical Observatory
    • Ben Hardesty, Lowell Observatory
    • Frank Cornelius, Lowell Observatory
  • Support

    Support for this project has come from and the generosity of the Yale alumni Community.