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 discovery of Pi Men c (some call it the first TESS planet): video, cnet, sciencenews, dailystar, sciencealert

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)

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 :)

See Günther, M.N. et al., 2019a

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.

See Günther, M.N. et al., 2018

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.

See Günther, M.N. et al., 2017b

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.

See Günther, M.N. et al., 2017a

(Artist illustration of NGTS-1b. Credit: University of Warwick/Mark Garlick)

2019

'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.

2018

Volunteered for a month with marine biologists in Mozambique, studying and teaching about marine conservation - sprinkled with some astrophysics.

2017

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).

2016

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).

2015

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 )