Publications by Tim Lichtenberg

Direct imaging of molten protoplanets in nearby young stellar associations

Astronomy and Astrophysics EDP Sciences 621 (2019) A125

I Bonati, T Lichtenberg, DJ Bower, ML Timpe, SP Quanz

© ESO 2019. During their formation and early evolution, rocky planets undergo multiple global melting events due to accretionary collisions with other protoplanets. The detection and characterization of their post-collision afterglows (magma oceans) can yield important clues about the origin and evolution of the solar and extrasolar planet population. Here, we quantitatively assess the observational prospects to detect the radiative signature of forming planets covered by such collision-induced magma oceans in nearby young stellar associations with future direct imaging facilities. We have compared performance estimates for near- and mid-infrared instruments to be installed at ESO's Extremely Large Telescope (ELT), and a potential space-based mission called Large Interferometer for Exoplanets (LIFE). We modelled the frequency and timing of energetic collisions using N-body models of planet formation for different stellar types, and determine the cooling of the resulting magma oceans with an insulating atmosphere. We find that the probability of detecting at least one magma ocean planet depends on the observing duration and the distribution of atmospheric properties among rocky protoplanets. However, the prospects for detection significantly increase for young and close stellar targets, which show the highest frequencies of giant impacts. For intensive reconnaissance with a K band (2.2 μm) ELT filter or a 5.6 μm LIFE filter, the β Pictoris, Columba, TW Hydrae, and Tucana-Horologium associations represent promising candidates for detecting a molten protoplanet. Our results motivate the exploration of magma ocean planets using the ELT and underline the importance of space-based direct imaging facilities to investigate and characterize planet formation and evolution in the solar vicinity. Direct imaging of magma oceans will advance our understanding of the early interior, surface and atmospheric properties of terrestrial worlds.

Magma ascent in planetesimals: control by grain size

Earth and Planetary Science Letters Elsevier 507 (2018) 154-165

T Lichtenberg, T Keller, R Katz, GJ Golabek, TV Gerya

Rocky planetesimals in the early solar system melted internally and evolved chemically due to radiogenic heating from 26Al. Here we quantify the parametric controls on magma genesis and transport using a coupled petrological and fluid mechanical model of reactive two-phase flow. We find the mean grain size of silicate minerals to be a key control on magma ascent. For grain sizes ≳1 mm, melt segregation produces distinct radial structure and chemical stratification. This stratification is most pronounced for bodies formed at around 1 Myr after formation of Ca, Al-rich inclusions. These findings suggest a link between the time and orbital location of planetesimal formation and their subsequent structural and chemical evolution. According to our models, the evolution of partially molten planetesimal interiors falls into two categories. In the magma ocean scenario, the whole interior of a planetesimal experiences nearly complete melting, which would result in turbulent convection and core–mantle differentiation by the rainfall mechanism. In the magma sill scenario, segregating melts gradually deplete the deep interior of the radiogenic heat source. In this case, magma may form melt-rich layers beneath a cool and stable lid, while core formation would proceed by percolation. Our findings suggest that grain sizes prevalent during the internal heating stage governed magma ascent in planetesimals. Regardless of whether evolution progresses toward a magma ocean or magma sill structure, our models predict that temperature inversions due to rapid 26Al redistribution are limited to bodies formed earlier than ≈1 Myr after CAIs. We find that if grain size was ≲1 mm during peak internal melting, only elevated solid–melt density contrasts (such as found for the reducing conditions in enstatite chondrite compositions) would allow substantial melt segregation to occur.

A water budget dichotomy of rocky protoplanets from 26Al-heating

Nature Astronomy Springer Nature 3 (2018) 307–313-

T Lichtenberg, GJ Golabek, R Burn, Meyer, Y Alibert, TV Gerya, C Mordasini

Impact splash chondrule formation during planetesimal recycling

Icarus Elsevier BV 302 (2018) 27-43

T Lichtenberg, GJ Golabek, CP Dullemond, M Schönbächler, TV Gerya, MR Meyer

Late metal–silicate separation on the IAB parent asteroid: Constraints from combined W and Pt isotopes and thermal modelling

Earth and Planetary Science Letters Elsevier BV 482 (2018) 490-500

AC Hunt, DL Cook, T Lichtenberg, PM Reger, M Ek, GJ Golabek, M Schönbächler

Was Planet 9 captured in the Sun’s natal star-forming region?

Monthly Notices of the Royal Astronomical Society: Letters Oxford University Press (OUP) 472 (2017) L75-L79

RJ Parker, T Lichtenberg, SP Quanz

The effects of short-lived radionuclides and porosity on the early thermo-mechanical evolution of planetesimals

Icarus Elsevier BV 274 (2016) 350-365

T Lichtenberg, GJ Golabek, TV Gerya, MR Meyer

Isotopic enrichment of forming planetary systems from supernova pollution

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 462 (2016) 3979-3992

T Lichtenberg, RJ Parker, MR Meyer

Modeling gravitational instabilities in self-gravitating protoplanetary disks with adaptive mesh refinement techniques

Astronomy & Astrophysics EDP Sciences 579 (2015) A32-A32

T Lichtenberg, DRG Schleicher