Architektura systémů exoplanet v porovnání se sluneční soustavou

• Název práce v češtině: Architektura systémů exoplanet v porovnání se sluneční soustavou
• Název v anglickém jazyce: Exoplanet systems versus Solar System architecture
• Klíčová slova: exoplanety
• Klíčová slova anglicky: exoplanets
• Akademický rok vypsání: 2024/2025
• Typ práce: disertační práce
• Ústav: Astronomický ústav UK (32-AUUK)
• Vedoucí / školitel: doc. Mgr. Miroslav Brož, Ph.D.
• Řešitel: skrytý - zadáno a potvrzeno stud. odd.
• Datum přihlášení: 09.09.2024
• Datum zadání: 09.09.2024
• Datum potvrzení stud. oddělením: 03.10.2024
• Konzultanti: RNDr. Ondřej Chrenko, Ph.D.

Zásady pro vypracování

Dynamics of exoplanet systems is more complex than just an N-body problem.
When these systems were forming, protoplanets were enshrouded by
gas, planetesimals, pebbles and dust, which altogether interacted.
For example:
protoplanets created spiral arms or waves in gas (Tanaka et al. 2002),
gas acted by aerodynamic drag on planetesimals (Nesvorný et al. 2024),
planetesimals formed when pebbles were concentrated (Johansen et al. 2007),
pebbles piled-up when dust condensed at an ice-line (Drążkowska et al. 2016),
etc.,
etc.,
etc..

One of the examples is a convergent migration of protoplanets,
explored recently by our team at the Institute of Astronomy
(Brož et al. 2021). When density and temperature profiles
of the gas disk support a convergence zone, the migration then
successfully explains observed Solar System architecture,
in particular, small separation of Venus and Earth (0.7 and 1 au),
as well as small sizes of Mercury and Mars (0.05 and 0.1 M_E).
Since a similar convergence zone is expected also around 5 au,
supporting a formation of Jupiter's core (Bitsch et al. 2014),
It follows that there must be a divergence zone in between.
This is where the current asteroid belt is located.

In this PhD project, we suggest to explore the effects of
the divergent zones (Task 1) and to test the model of
convergent migration in selected exoplanet systems (Task 2).

Specifically, the student should prepare a computational model
(either hydrodynamical, or simplified N-body) suitable
for protoplanets and planetesimals migrating/moving in
a divergent zone. The model has to include not only classical
Type-I torques (Paardekooper et al. 2011), but also
the hot-trail effect (Chrenko et al. 2017), and
possibly other thermal effects (Cornejo et al. 2023).
The formation of planetesimals within the asteroid belt
and their possible evolution should be discussed.
They can form either in an extended region, or locally,
at the Si-, C- or ice-line (Morbidelli et al. 2022).
The model should be compared to the observed distributions
of major classes of asteroids/meteorites (H, L, LL, CM, CI;
Anderson et al., submit.).

It might be interesting to take into account radiometric ages
(crystallisation, shock, exposure) and isotopic signatures
measured in major classes of meteorites (Kruijer et al. 2017).
These might be related to inflows from chemically distinct
reservoirs and mixing (Burkhardt et al. 2019).

Regarding an application to other exoplanet systems,
one suggestion might be, for example, TOI-178 (Leleu et al. 2021).
It is a six planet system (b, c, d, e, f, g), in which individual
masses and sizes were constrained by transit observations.
The current radial positions of planets correspond to a 'chain'
of mean-motion resonances (3:5, 1:2, 2:3, 2:3, 3:4).

The student should prepare a computational model of an exoplanet system
in its early stage, when low-mass protoplanets were forming,
growing, migrating, merging, or encountering each other.
Again, interactions with a gas disk must be taken into account.
As for the disk profiles, possible locations of important
transitions could be constrained (see, e.g., Ueda et al. 2017)
For a broader context, discussion of planetary atmospheres
is needed; they also determine the resulting densities of planets.

For computations, it is possible to use the symplectic integrator
Symba (Duncan et al. 1998) or the hydrodynamical code Fargo
(Benítez-Llambay & Masset 2016), or their alternatives.

Seznam odborné literatury

Anderson, S. et al., Different arrival times of CM and CI-like bodies
from the outer Solar System to the asteroid belt. Nat. Astron. submit.

Benítez-Llambay, P. Masset, F., FARGO3D: A new GPU-oriented MHD code.
Astrophys. J. Suppl. Ser. 223, 11, 2016.

Bitsch, B. et al., Stellar irradiated discs and implications on migration
of embedded planets. II. Astron. Astrophys. 564, A135, 2014.

Brož, M et al., Early terrestrial planet formation by torque-driven
convergent migration of planetary embryos. Nat. Astron. 5, 898, 2021.

Burkhardt, Ch. et al., Elemental and isotopic variability in solar system
materials by mixing and processing of primordial disk reservoirs.
Geochim. Comochim. Acta 261, 145, 2019.

Chrenko, O. et al., Eccentricity excitation and merging of planetary
embryos heated by pebble accretion. Astron. Astrophys. 606, A114, 2017.

Cornejo, S. et al., On the interaction of pebble accreting embryos with
the gaseous disc: importance of thermal forces. Mon. Not. R. Astron. Soc.
523, 936, 2023.

Drążkowska, J. et al., Close-in planetesimal formation by pile-up of
drifting pebbles. Astron. Astrophys. 594, A105, 2016.

Duncan, M.J. et al., A multiple time step symplectic algorithm for
integrating close encounters. Astron. J. 116, 2067, 1998.

Johansen, A. et al., Rapid planetesimal formation in turbulent circumstellar
disks. Nature 448, 1022, 2007.

Kruijer, T.S. et al., Age of Jupiter inferred from the distinct genetics
and formation times of meteorites. Proc. Nat. Acad. Sci. 114, 6712, 2017.

Leleu, A. et al., Six transiting planets and a chain of Laplace resonances
in TOI-178. Astron. Astrophys. 649, A26, 2021.

Morbidelli, A. et al., Contemporary formation of early Solar System
planetesimals at two distinct radial locations. Nat. Astron. 6, 72, 2022.

Nesvorný, D. et al., Isotopic trichotomy of main belt asteroids from
implantation of outer solar system planetesimals. Earth Planet. Sci. Lett.
626, 118521, 2024.

Paardekooper, S.-J. et al., A torque formula for non-isothermal Type I
planetary migration. II. Effects of diffusion. Mon. Not. R. Astron. Soc.
410, 293, 2011.

Tanaka, H. et al., Three-dimensional interaction between a planet and
an isothermal gaseous disk. Astrophys. J. 565, 1257, 2002.

Ueda, T. et al., Analytic expressions for the inner-rim structure of
passively heated protoplanetary disks. Astrophys. J. 843, 49, 2017.