J.E.S. - 2015
I am a Research Astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. My research focuses on low-mass stars near the Sun and the planets they host. These stars, the M dwarfs, with masses <0.6 Solar masses and temperatures <4000 K, comprise >70% of the Galactic stellar content. I lead a program to use the unprecedented sensitivity of the James Webb Space Telescope (JWST) to directly image sub-Jupiter mass planets on wide orbits around nearby, young M dwarfs. I also collaborate on a large and very successful project to identify, validate, and characterize small planets on close orbits around low-mass stars from K2, the re-purposed Kepler telescope. I am currently developing plans for low-mass star planet research using the upcoming Transiting Exoplanet Survey Satellite (TESS), scheduled for launch in Spring 2018. Searching for both the massive outer planets and small inner planets of M dwarfs will provide a comprehensive view of planet formation, evolution, and demographics around our most numerous stellar neighbors. See my Research page for further details.
Two Super-Earths Near Resonance Orbiting a Nearby Cool Star
Fast Moving Features in a Nearby Debris Disk
Top: Calibrated K2 light curve of the nearby, bright, low-mass star K2-21. The star hosts two close in, super-Earth planets whose transits are designated with the blue and red ticks. Bottom: Phase folded photometry of the planets with best-fit light curve models. The planets are ~2 Earth radii, have estimated equilibrium temperatures <600K, and have periods close to the 5:3 mean motion resonance. These planets are ideal targets for future follow-up including radial velocity monitoring, transit timing variations, and transit spectroscopy. Their discovery and characterization is described in Petigura, Schlieder, et al. 2015.
Left: Images of the edge-on debris disk orbiting the nearby, ~20 Myr, low-mass star, AU Microscopii (AU Mic). The images were obtained with the Hubble Space Telescope (HST) in 2010 and 2011 and the SPHERE exoplanet imager at the VLT in 2014. The star is masked behind the black circle in the middle. In the HST images, several bumps or asymmetries are visible on the left side of the disk. The SPHERE images resolve these into several arch or wave-like features. The top bar illustrates the size of Neptune's orbit for scale. Right: The same sequence of images zoomed in on the left side of the disk and smoothed and subtracted to highlight the observed dust features. The arrows connect like features imaged during the 3 epochs separated by 4 years and reveal that they are moving outward away from the star. Such dynamic features have never before been observed in a debris disk and were a completely unexpected discovery. It is unclear what drives their motion, but the outermost features are moving at velocities fast enough to escape the gravitational pull of the star. Further observations are required to understand their nature and origin. The discovery of these features and a full analysis is presented in Boccaletti et al. 2015 [Image credit: NASA, ESO, ESA, A. Boccaletti].
Mapping the Orbit of a Nearby Binary
Left: LBTI/LMIRCam images of the nearby, 500 Myr, late-type binary, NO UMa from the LEECH Exoplanet Imaging Survey. The top image was obtained in April 2013. The two components are blended and the intensity distribution is elongated in the north-south direction. The bottom image was obtained in December 2013 and both components are clearly resolved. Between April and December, the secondary moved counter-clockwise nearly 180 degrees. Right: Observed positions of the secondary with respect to the primary from adaptive optics imaging (orange circles) and speckle interferometry (blue squares), including the images in the left panel (2013.31 and 2013.99). The imaging data was combined with spectroscopic velocity curves to perform a joint fit of the orbit and derive the orbital parameters (blue ellipse). The fit reveals an eccentric orbit with a period of 3.5 yr and primary and secondary masses of 0.83 and 0.64 solar masses, respectively. The measured masses are in excellent agreement with predictions from stellar evolution models. NO UMa joins the short list of nearby binaries with fully characterized orbits and known ages. The full analysis of the system and further information regarding the LEECH survey is published in Schlieder et al. 2016.