Exoplanets and Travelling
+ Data Science and Public Engagement
A short introduction of myself
Hi! I am an astrophysicist hunting for new exoplanets. Since 2018, I am a Torres Fellow at the Massachusetts Institute of Technology (MIT), working with the Transiting Exoplanet Survey Satellite (TESS) team. Whenever I am not searching for new worlds, I enjoy travelling, the outdoors (scuba diving, rock climbing and hiking), and exploring our own Earth.
Expertise: Exoplanets, Stellar Flares, Cool Stars, Habitability
Skills: Bayesian Statistics, Machine Learning, Time Series Analysis
My PhD was obtained at the University of Cambridge, UK, where I worked in Professor Didier Queloz's group at the Exoplanet Research Centre. My research was focused on how we can distinguish between real exoplanets and stuff that looks like exoplanets, but is not ("false positives"). I worked with the Next Generation Transit Survey, a ground-based array of telescopes on the hunt for Neptune-sized exoplanets.
For my Master’s Thesis, I did something completely different: research in the biophysics lab of Professor George Shubeita at the University of Austin at Texas ("hook 'em horns"). I developed a mathematical model furthering our understanding of animal models of genetic diseases like Alzheimer's and Fragile X.
My physics undergraduate education was at the University of Würzburg, where I studied AGN mega-masers in the multi-wavelength group of Professor Matthias Kadler.
(Yellowstone. Credit: M. Günther)
Sep 18, Started as a Torres Fellow at MIT, working closely with the TESS science team
Aug 18, Volunteered with Love The Oceans in Mozambique: marine biology field work, scuba diving, and work with the local schools
July 18, Graduated from the University of Cambridge with a PhD in (astro-)physics
Apr 18, Launch of TESS on the SpaceX Falcon 9 from Cape Canaveral
Oct 17, Meeting Nobel laureate Rainer Weiss on the day of his award
Sep 16, Advancing my Spanish for a month at Universidad de La Habana, Cuba with an A.J. Pressland Fund scholarship
Feb 16, Joined Prince Philip, Duke of Edinburgh, and Ambassador Ammon for the Kurt Hahn Dinner in the German Embassy in London
Apr 15, My first visit to Paranal: working on NGTS, and exploring the worlds driest desert, Atacama, and its unbelievable night sky
Jul 15, Discussing my research with Prince Andrew, Duke of York, during his visit to Cambridge's Astrophysics Groups
Oct 14, Started my PhD at the University of Cambridge
My research teams
The Transiting Exoplanet Survey Satellite (TESS)
The Transiting Exoplanet Survey Satellite (TESS) is set to discover thousands of new exoplanets. Launched in April 2018, TESS now monitors millions of stars for temporary drops in brightness, which are caused by planetary transits. It will identify planets ranging from Earth-sized to gas giants, around a wide range of stellar types and orbital distances - and maybe even Earth 2.0.
The TESS discover of HD 21749 b and c (TESS' first Earth-sized planet): New York Times
The Next Generation Transit Survey (NGTS)
The Next Generation Transit Survey (NGTS) is an exoplanet hunter based in Paranal, Chile. With its 12 fully robotized 20 cm telescopes, NGTS covers a total field of view of almost 100 sq. deg. on the sky at once. The main goal of NGTS is to find transiting Neptunes that will be suitable for RV follow-up and mass measurements using current and future instruments such as HARPS and ESPRESSO.
(Launch of TESS. Credit: M. Günther)
Summary of my research
How do stellar flares impact habitability?
Why care about flares? Because flares can impact habitability - they may erode exoplanets' atmospheres, but might also trigger the genesis of life. And all of this is especially important around M-dwarfs! To model flares, we use our public allesfitter code (Günther&Daylan, in prep.). It not only models exoplanets&binaries and red noise (with GPs), but also robustly selects the appropriate model for potentially complex flares via Bayesian evidence. Using Nested Sampling, we can compute the Bayes factors of diffferent models - pure noise, 1 flare, 2 flares, and so on. So what do we find? From the sample of ~25,000 TESS objects we find ~760 flaring stars, ~630 of which are M-dwarfs. Especially the mid M-dwarfs are `flary'. And one of the coolest (no pun intended) things: TESS explores so many bright early to late M-dwarfs! Of course, thanks to Kepler/K2/NGTS/MEarth/EVRYSCOPE and others we already learned some things about their flares - but TESS truly opens up new avenues here. Moreover, we find that fast rotating M-dwarfs are the most likely to flare, solidifying previous findings by other studies. And one of my personal favorites: the large amplitude flare on an M4.5 dwarf, raising the stellar brightness by a factor of 15.7! This goliath is even preceeded by a series of `warm-up' flares. Finally, we link all this flaring to prebiotic chemistry, coronal mass ejections, and ozone depletion. This figure contains a lot of info, and a detailed explanation is beyond this tweet - so if all this raised your interest, have a look at the paper :)
Unmasking the hidden NGTS-3Ab
NGTS-3 is a very tricky system: at first it looked like a 'simple' Hot Jupiter around a Sun-like star. After taking some radial velocity measurements, it suddenly appeared that there is some 'funkyness' in the data. So it was nearly disregarded as a false positive. After extensive analysis, however, we could save this happy big planet: it turned out to be a Hot Jupiter in a previously (and still visually) unresolved binary star system.
Identifying false positives by measuring stellar light to 0.00025 image pixel
Astrophysical false positives are crucial to avoid in a wide-field transit survey like NGTS. Eclipsing binaries with a low-mass companion or grazing eclipses, as well as diluted eclipsing binaries or variable stars in the background can mimic a planet transit and be very costly to follow up. They can best be identified with the centroiding technique: if the photometric flux is lost off-centre during an eclipse, the flux centroid shifts towards the centre of the target star. Although this method has successfully been employed by the Kepler mission, it has previously not been proven feasible from the ground. A new algorithm I developed allows NGTS to detect centroid shifts with a precision of down to 0.00025 pixel. This makes NGTS the first ground-based wide-field transit survey ever to successfully implement this technique for candidate auto-vetting.
Optimizing the yield of transit surveys
YETI (Yield Estimator for Transit Instruments) is a Python-based simulator I developed to estimate the yield of planets and false positives for transit surveys like NGTS, Kepler and TESS. It enables to evaluate the influence of field selection, observing strategies, noise properties, detection criteria and false alarm rates. Further, with YETI one can diagnose methods for candidate vetting, and establish appropriate follow-up strategies.
(Artist illustration of NGTS-1b. Credit: University of Warwick/Mark Garlick)
Peer-reviewed, lead author
- Günther, M.N. et al., 2019b, A Super-Earth and two sub-Neptunes transiting the bright, nearby, and quiet M-dwarf TOI-270, Nature Astronomy, 409
- Günther, M.N. et al., 2019a, Stellar Flares from the First Tess Data Release: Exploring a New Sample of M-dwarfs, in review (arXiv:1901.00443)
- Günther, M.N. et al., 2018, Unmasking the hidden NGTS-3Ab: a hot Jupiter in an unresolved binary system, MNRAS, 478 (4): 4720–4737
- Günther, M.N. et al., 2017b, Centroid vetting of transiting planet candidates from the Next Generation Transit Survey, MNRAS, 472 (1): 295-307
- Günther, M.N. et al., 2017a, A New Yield Simulator for Transiting Planets and False Positives: Application to the Next Generation Transit Survey, MNRAS, 465 (3): 3379-3389
- Günther, M.N. et al., 2016, Quantifying and predicting Drosophila larvae crawling phenotypes, Nature Scientific Reports, 6: 27972
Peer-reviewed, co-lead author
- Zhan, Z., Günther, M. N., et al., 2019, Complex Rotational Modulation of Rapidly Rotating M-Stars Observed with TESS, ApJ, 876: 127
- Dragomir, D., Teske, J., Günther, M.N., et al. 2018, TESS delivers its first Earth-sized planet and a warm sub-Neptune, ApJ, 875: L7
- Huang, C.X., Burt, J., Vanderburg, A., Günther, M.N., et al. 2018, TESS Discovery of a Transiting Super-Earth in the Pi Mensae System, ApJ, 868 (2): L39
- Armstrong, D.J., Günther, M.N., et al., 2018, Automatic vetting of planet candidates from ground-based surveys: machine learning with NGTS, MNRAS, 478 (3): 4225–4237
- West, R.G. et al. incl. Günther, M.N., 2019, NGTS-4b: A sub-Neptune transiting in the desert, MNRAS, 486: 5094
- Osborn, H.P. et al. incl. Günther, M.N., 2019, The PDS 110 observing campaign - photometric and spectroscopic observations reveal eclipses are aperiodic, MNRAS, 485: 1614
- Rodriguez, J.E. et al. incl. Günther, M.N., 2019, An Eccentric Massive Jupiter Orbiting a Sub-Giant on a 9.5 Day Period Discovered in the Transiting Exoplanet Survey Satellite Full Frame Images, , AJ, 157: 191
- Shporer, A. et al. incl. Günther, M.N., 2019, TESS Full Orbital Phase Curve of the WASP-18b System, AJ, 157: 178
- Eigmüller, P. et al. incl. Günther, M.N. 2019, NGTS-5b - a highly inflated planet offering insights into the sub-Jovian desert, A&A, 625: A142
- Songhu, W. et al. incl. Günther, M.N., 2019, HD 202772A b: A Transiting Hot Jupiter around a Bright, Mildly Evolved Star in a Visual Binary Discovered by TESS, AJ, 157, 51.
- Jackman, J. et al. incl. Günther, M.N., 2019, Detection of a giant flare displaying quasi-periodic pulsations from a pre-main-sequence M star by the Next Generation Transit Survey, MNRAS, 482 (4): 5553-5566
- Raynard, L., et al. incl. Günther, M.N., 2018, NGTS-2b: An inflated hot-Jupiter transiting a bright F-dwarf, MNRAS, 481, 4960–4970
- Casewell, S., et al. incl. Günther, M.N., 2018, A low-mass eclipsing binary within the fully convective zone from the Next Generation Transit Survey, MNRAS, 481 (2): 1897–1907
- Jackman, J. et al. incl. Günther, M.N., 2018, Ground-based detection of G star superflares with NGTS, MNRAS, 477 (4): 4655–4664
- Bayliss, D. et al. incl. Günther, M.N., 2017, NGTS-1b: a hot Jupiter transiting an M-dwarf, MNRAS, 475 (4): 4467-4475
- Wheatley, P. et al. incl. Günther, M.N., 2017, The Next Generation Transit Survey (NGTS), MNRAS, 475 (4): 4476-4493
- Demory, B.-O. et al. incl. Günther, M.N., 2015, Hubble Space Telescope search for the transit of the Earth-mass exoplanet Alpha Centauri B b, MNRAS, 450 (2): 2043-2051
- Günther, M.N. & Daylan, T., 2019, allesfitter: Flexible star and exoplanet inference from photometry and radial velocity, Astrophysics Source Code Library (ascl:1903.003)
- Günther, M.N., 2018, Identifying Exoplanets and Unmasking False Positives with NGTS
(NGTS in Paranal, Chile. Credit: G. Lambert )
'Ask/Tell a Scientist' at the Science Festival in Cambridge, MA, USA: Enagaged in open discussions with the public about any scientific topic, from astronomy to biology.
Volunteered for a month with marine biologists in Mozambique, studying and teaching about marine conservation - sprinkled with some astrophysics.
Hosted a public evening on exoplanets in Burgkunstadt Germany, and gave a visiting tutorial for the high school's astrophysics course. Featured in the local German news (web1, web2) and on the school's website (web1, web2).
Tutored high-performing high-school students in physics and astronomy over multiple months, as part of 'The Brilliant Club' - a charitable programme focussed on low-participation neighbourhoods (web).
Bringing exoplanet science to 8-12 year old pupils in Barton Road and Milton Road Primary Schools. Thanks to the Cambridge Science Festival Roadshow for this fantastic programme (leaflet).
Initiated a public evening on exoplanets hosted at my former high school, Gymnasium Burgkunstadt, in Germany. The evening was featured in articles in the Obermain Tagblatt (web) and on the school's website (web).
(Outreach event, Germany. Credit: OT/Adriane Lochner )
Department of Physics,
and Kavli Institute for Astrophysics and Space Research
Massachusetts Institute of Technology
Cambridge, MA 02139, USA
Email: maxgue [at] mit.edu
(Sunset at Paranal, Chile.
Credit: M. Günther)