Subproject 5: Structure and thermal evolution models for Neptune-like planets

PI: N. Nettelmann, PhD: L. Scheibe

The primary purpose of this project is to develop coherent interior structure and evolution models for Uranus and Neptune. Furthermore, we plan to provide relations between the predicted internal structure and the value of the fluid Love number k2,f for Neptune-like exoplanets. This projects serves Key Question B "What is the interior structure of Neptune-like planets ?" and Key Question C "How can we distinguish between super-Earths and mini-Neptunes ?" of the Overall Project of this Research Unit.


Illustration of the possible internal structure of an ice giant planet, and of the unknowns.

Uranus and Neptune

This objective is important for understanding Neptune-like planets as class of planets. So far, none of the models for Uranus and Neptune can consistently explain the observed luminosity, the gravity fields, and the magnetic fields. In this context we will investigate

  • what internal configurations (temperature profiles and composition profiles) are consistent with both the observed luminosities and the gravity field?
  • are there stably stratified regions in the interior?
  • where is the magnetic field generated?
  • what are the possible bulk compositions and initial states for models that do meet the above constraints?
Love number k2 measurements of Solar system planets, and Love number k2f predictions for the mini-Neptune GJ1214b.

Neptune-like planets and the love number k2,f

The Love number k2 has been measured for a number of planets in the Solar system. The fluid Love k2f in particular yields the surface potential response of a planet that is in tidal equilibrium with its tidal perturber. Candidates are fluid planets such as Saturn, which adjust quickly , or exoplanets locked into a 1:1 resonance with the parent star. The more homogeneous the internal mass distribution of a planet is, the larger will be the value fo k2f. For instance, water envelopes will yield a higher k2f value that H/He envelopes on-top a rocky core of Neptune-like planets. This is illustrates in Figure 2 for the mini-Neptune GJ1214b. We will use the property to determine the internal mass distribution of Neptune-like exoplanets. In contrast, rocky planets in the Solar system are not in tidal equilibrium with their perturber: the Love number depends on the internal rheoplogy and adopts smaller values than the theortical k2f value (Earth, Mars).


This project is affiliated to the AG Statistische Physik.

Contact PI

Dr. Nadine Nettelmann, Institut für Physik, Universität Rostock 
Albert-Einstein Str. 23, Room 150
Tel. +49 (0)318 498 6916, Email