Brett M. Morris

Characterizing exoplanets and their host stars

I am a sixth year PhD candidate in the dual-title PhD Astronomy and Astrobiology Program at the University of Washington in Seattle. My research interests sit at the intersection of characterizing exoplanets and their host stars. I work with ground and space-based observations to measure the properties of planet-hosting stars, and their effects on our measurements of the compositions and structures of exoplanets.

You can find my curriculum vitae (CV) in PDF form here, or you can scroll down for an abridged web version.

Stellar Activity

Starspot Mapping of HAT-P-11

Spot occultations of HAT-P-11

We only know as much about an exoplanet as we know about its host star, which is why I collaborate with Professors Leslie Hebb (HWSC), Suzanne Hawley (UW) and Dr. James Davenport (WWU) on Kepler observations of spotted host stars of transiting planets. Transits allow us to break degeneracies and locate star spots on the surface of the star with precision from photometry alone.

The K4 dwarf HAT-P-11 hosts a hot Neptune planet, which we use as a mini-coronograph to study the starspots of the host star. The spots are distributed in latitude similar to sunspots at solar activity maximum, though the area covered by spots is 100x greater than the typical solar spot coverage. Our analysis of starspots on HAT-P-11 has been published in the Astrophysical Journal, read the paper here, or watch my presentation on HAT-P-11 at Cool Stars 20 here.

Chromospheric Activity

CaII H chromospheric activity of HAT-P-11

HAT-P-11 seems to have a Sun-like spot distribution, but is the overall amount of activity on HAT-P-11 normal among stars of its mass and rotation period/age? To find out, I calibrated the APO Echelle Spectrograph to measure Mount Wilson S-indices of chromospheric activity. It seems HAT-P-11 is more active than planet hosts of similar mass and rotation period, and we suggest that the tides induced by the close-in planet may be to blame.

Our analysis of the chromospheric activity of HAT-P-11 was recently publishied in the Astrophysical Journal, read here.

Reparameterizing the transit light curve with robin

A spot map that interferes with the transit depth; not a problem for robin!

If a star is sufficiently contaminated by bright or dark regions, the transit depth that we observe with photometry is likely not equivalent to the square-root of the ratio of planet to stellar radii. However, the planet's radius is still encoded in the transit light curve in the ingress and egress durations. In a paper recently accepted by AJ, we introduce a simple reparameterization to the Mandel and Agol (2002) transit model which allows you to fit for the planet radius, even in the presence of significant contamination by bright or dark regions on the stellar surface.

Ground-based photometry of HAT-P-11 b

Solar astrometric shifts due to starspots

As the stellar activity cycle of HAT-P-11 progresses, I am monitoring HAT-P-11's starspots from the ground with the ARC 3.5 m Telescope at APO, using a holographic diffuser for precision photometry (see details here). In this Research Note, we find that HAT-P-11 was more spotted than ever before in late 2017.

Spotting activity with Gaia Astrometry

Solar astrometric shifts due to starspots

As spots rotate into and out of view, the apparent centroid of the star appears to shift by tiny fractions of a stellar radius. The Gaia mission will measure stellar centroids with sufficient precision to resolve centroid shifts due to activity. We build a small sample of candidate targets for astrometric activity observations with Gaia in a paper recently accepted by MNRAS.

The plot above shows reconstructed observations of the Sun from Mount Wilson Observatory near solar maximum, and the associated photocenter shifts due to spots and rotation.

The Stellar Variability of TRAPPIST-1

Bright starspot model for TRAPPIST-1

By comparing the out-of-transit rotational variability of TRAPPIST-1 in the Kepler and Spitzer bandpasses, we can constrain the properties of its starspots. In a paper recently accepted by ApJ, we show that bright active regions can explain the variability observed with both K2 and Spitzer. We also find that flares seem correlated with increasing stellar brightness, perhaps suggesting that the variability in the Kepler band is not a rotational signal after all.

Exoplanet Characterization

Transit Timing Variations


I work with Professor Eric Agol (UW) and Dr. Carolina von Essen (Aarhus University) on characterizing exoplanet systems with transit timing variations with Kepler and ground-based observations from the ARC 3.5m telescope at Apache Point Observatory as part of the KOINet collaboration (read on here).

The transit at left is the Earth-sized exoplanet TRAPPIST-1 b, observed with the ARC 3.5 m Telescope at APO with the ARCTIC imager and holographic diffuser (see my Research Note on transit times in the TRAPPIST-1 system below).

Transmission spectroscopy

Keck Observatory

I also collaborate with Dr. Avi Mandell (NASA GSFC) on characterizing giant exoplanet atmospheres with transmission spectroscopy in the near-infrared using my own observations from Keck/MOSFIRE (PI Morris, 2014).

Mentorship: Planet hunting

Ada Beale, Doug Branton

I founded and lead the Search for Planets Around post-Main Sequence stars (SPAMS) group at the University of Washington, an undergraduate effort to use small aperture ground-based telescopes to find transiting planets/debris orbiting white dwarfs at short periods. Our preliminary results were recently published in RNAAS.


Microbial ecology at Yellowstone

As a dual-title PhD in astronomy and astrobiology, I am privileged to work with interdisciplinary scientists. For my astrobiology research rotation, I am developing a comprehensive data reduction and analysis pipeline with Professor Jody Deming (UW) on the Submersible Holographic Astrobiology Microscope with Ultraresolution.

I am learning to reconstruct phase and intensity images from a digital holographic microscope, and to develop analysis software scalable to high-throughput computing facilities. The reconstruction pipeline I built, called shampoo, is in active developement and is being used by our research group.


See my full list of publications and proceedings on ADS here, or just first-author papers here.


First Author Papers

Research Notes

nth Author Papers

You can find my CV in PDF form here.

Selected Proceedings and Proposals

Open Software

Here's some more open source software I wrote to make your day better:

  • mrspoc: Compute astrometric centroid offsets due to starspots for nearby Gaia stars [paper]
  • aesop: handling echelle spectra from the ARC 3.5 m Telescope at APO paper]
  • Pre-MAP: my intro to Python curriculum for the 2016 Pre-Major in Astronomy class lots more contributions on GitHub!

Honors and Awards

  • UW Graduate Student Research Award, 2018
  • Poster competition winner at the NASA Kepler Science Conference IV (earned prize talk presentation)
  • Pacific Science Center Science Communication Fellow (2016)
  • Chambliss Astronomy Achievement Graduate Student Award Honorable Mention. 225th AAS, Seattle, WA (2015), and 222nd AAS, Indianapolis, IN (2013)
  • Astrobiology Fellow, University of Washington, 2013-2014


Astronomy on Tap

I am co-founder/co-organizer of the popular Astronomy on Tap Seattle public astronomy talk series. I coordinate with speakers, write trivia, present on current astro-news, and have the most fun as the MC and as an occassional speaker. The video at left is an AoT talk I gave on the mysterious Boyajian's Star.

Pre-Major in Astronomy Program

Pacific Science Center (photo cred: Lisa C.)

I have been the instructor (2016) and academic mentor (2015) for the UW's Pre-MAP program for freshmen undergraduates with interests in astronomy who are traditionally underrepresented in astronomy. We set them up with (1) computer programming skills, (2) research skills, (3) a research project in their first quarter of their first year with attentive mentorship and peer support.

Digital Outreach

For fun (and for science!) I maintain a small army of Twitter Bots that do science outreach at all times while I do other things. The army consists of:

  • @planetTVguide: Accounting for light travel time between planets, it tells you when premiere TV broadcasts of historic shows reach known exoplanets in real time
  • @transitingnow: Demonstrating the vast number of transiting exoplanets with real-time tweets when each transiting exoplanet appears to pass in front of its star
  • @farawayplanets: If observers on distant planets had telescopes that could see what is happening on Earth and they looked right now, this is what they would see

The TwitterBots have gotten some attention in the press lately. See below for links, and a video based on my TwitterBot @farawayplanets!