Dr. Jens Kammerer

Research Fellow at European Southern Observatory, Garching, Germany

About me

Hey there! I am an astrophysicist working on direct observations of exoplanets and brown dwarfs. Using the world's largest ground- and space-based telescopes, I am studying these objects' size, temperature, atmosphere, and orbital motion to learn how they came into existence, how they evolve throughout time, and how common they are. For this purpose, I take direct images of young planetary systems in the infrared, where exoplanets and brown dwarfs still glow bright from their remaining formation heat. However, such direct observations of exoplanets are very challenging because the thermal glow of the planets is more than 10'000 (ten thousand) times fainter than the bright light of their host stars which are located nearby on the sky. By the way, the bright dot on the background image is our own planet Earth imaged by the Voyager 1 spacecraft from a distance of about 6'000'000'000 (six billion) kilometers and is a fairly well representation of how our images of exoplanets look like (the planets only ever appear point-like).

My current research focuses on high-contrast imaging surveys with GRAVITY & SPHERE. GRAVITY combines the light from four 8.2 m telescopes and allows us to see exoplanets and brown dwarfs closer to their host stars than traditional imagers using only a single telescope. This means we are sensitive to companions that also the Gaia space telescope can detect, and data from Gaia helps us to select our targets and determine accurate companion masses once we detect them also directly with GRAVITY. SPHERE is a traditional imager using the light from only a single telescope, but it has an interferometric observing mode called Sparse Aperture Masking (SAM) which greatly improves its spatial resolving power. With SAM, we are searching for close-in brown dwarfs and low-mass stellar companions to targets in the beta Pictoris Young Moving Group (YMG). These same targets are also observed by a JWST coronagraphy survey, and by combining SPHERE/SAM and JWST, we will be sensitive to a broad range of companion masses and orbital separations and obtain the most comprehensive census of exoplanets in the beta Pictoris YMG to date.

Before I moved to ESO in Germany, I worked at the Space Telescope Science Institute in the US on the James Webb Space Telescope (JWST), NASA's new flagship mission. JWST features a 6.5 m large gold-coated primary mirror, the largest mirror ever launched into space, and enables observations of exoplanets at wavelengths that are inaccessible from the ground due to the Earth's atmosphere. Moreover, JWST is capable of directly detecting fainter and therefore less massive planets than ever before. At STScI, I became part of the JWST Telescope Scientist Team where we observed known exoplanetary systems to explore the new parameter space opened up by JWST. For instance, we detected a curious tail of material being lifted off the disk around beta Pictoris, probably as a consequence of colliding asteroids in its circumstellar debris disk (see our press release). Besides, I have also been part of the JWST Commissioning Team and helped to characterize the on-sky performance of its high-contrast imaging modes. Following commissioning, I participated in the JWST Early Release Science program and developed the first version of spaceKLIP, a dedicated and now widely used data reduction pipeline for JWST high-contrast imaging observations, together with my collaborators. I am also the PI of two JWST Cycle 1 programs that exploit the use of SAM and the closely related kernel phase technique on JWST.

Apart from that, I am also involved with future mission studies that could, for the first time, directly detect and characterize the atmospheres of Earth-like exoplanets. To understand the potential capabilities of these missions, and to make choices about their eventual design, it is important to predict how many and what kind of exoplanets they would be able to detect, and how various sources of noise can impact these detections. I am actively involved in the European LIFE Space Mission concept through leading the Instrument Science Team and conducting exoplanet yield estimates, and I also developed a simulator for NASA's Habitable Worlds Observatory concept and used it to characterize the impact of exozodiacal dust on our ability to detect Earth-like exoplanets in reflected light.

Characterization of HD 206893 B

In this work, we study the orbit and atmosphere of the reddest known sub-stellar companion HD 206893 B by combining our new GRAVITY data with GPI, SPHERE, and NACO data from the literature. GRAVITY's exquisite astrometric precision reveals a possible misalignment between the orbit of HD 206893 B and the debris disk of the system and the observed spectrum supports sub-micron sized dust particles in the cool upper atmosphere causing the extreme color of HD 206893 B. However, future observations are required to determine whether HD 206893 B is a gas giant planet or a brown dwarf.

Disk extinction in T Tauri triple system

In this work, we study the mid-infrared photometry of all three stars in the famous T Tauri triple system. To separate the tight southern binary star at 10 microns, we apply the kernel-phase high-resolution imaging technique. We find a decrease in the mid-infrared brightness of T Tauri Sb, consistent with a recent dimming observed in the near-infrared. This supports the hypothesis that T Tauri Sb has moved along its orbit behind the southern circumbinary disk and now suffers from increased dust extinction and confirms the presence of multiple misaligned disks in the young T Tauri system.

Pushing GRAVITY to deeper contrasts

In this work, we improve the detection limits for faint companions of the GRAVITY instrument at ESO's Very Large Telescope Interferometer in the North of Chile. This is achieved by studying and modeling the correlated errors which affect GRAVITY. When using our error correlation model in the companion search process, we are able to find more than two times fainter companions if compared to when only considering uncorrelated errors. Moreover, the robustness of statistical 3-sigma detections increases tremendously and false positive detections become much rarer.

Searching for young giant planets

In this work, we are searching for young gas giant exoplanets in the Taurus star-forming region (SFR). Forming planets in this extremely young region should be particularly bright and therefore easier to find than their older counterparts, but due to the larger distance of the Taurus SFR if compared to nearby moving group targets, we need to achieve a higher resolution to be able to resolve Solar System scales. This is achieved with the so-called kernel-phase technique, which can detect companions below the classical diffraction-limit of a telescope.

Kernel-phase from the ground

In this work, we search for faint companions at close separations around a sample of 28 nearby field stars. For this purpose, we apply the kernel-phase technique to archival ground-based NACO data and detect two stellar companions at or below the classical diffraction-limit, one of which was previously unknown. We also develop detector linearity, bad pixel, and saturation correction and principal component calibration algorithms that are applicable to Fourier plane imaging techniques in general.

Finding habitable extrasolar worlds with LIFE

In this work, we predict the number and properties of exoplanets that could be detected with a future space-based formation-flying nulling interferometer operating in the mid-infrared, such as the LIFE mission concept that we recently proposed for ESA's Voyage 2050 program. The mid-infrared wavelength regime is ideal to study the thermal emission of temperate Earth-like exoplanets and to characterize the composition of their atmospheres. With such a mission, we could find the first habitable planets outside our Solar System.

Resources

Publications

My publications on Google Scholar.

Software

My software on GitHub.

fouriever

A toolkit for calibrations, correlations, and companion search in kernel-phase, aperture masking, and long-baseline interferometry data.

NIRCCoS

A pipeline for simulating NIRCam coronagraphy data based on JWST APT files.

P-pop

A toolkit for simulating synthetic exoplanet populations based on Kepler and radial velocity statistics.

P-pop Photometry

An addition to P-pop for computing the observed fluxes of the synthetic exoplanets and their host stars.

HotSci talk

My HotSci talk about the direct characterization of gas giant exoplanets with optical long-baseline interferometry.

HLTau talk

My HLTau conference talk about planet formation with near-infrared interferometry.

Contact

If you have questions about my research, my software, or anything else, please feel free to send me an email at Jens.Kammerer (at) eso.org. A continuously updated list of all science staff at ESO Garching can be found here.