The Motion of Chondrules and Other Particles in a Protoplanetary Disk with Temperature Fluctuations

The Motion of Chondrules and Other Particles in a Protoplanetary Disk with Temperature Fluctuations

Authors:

Loesche et al

Abstract:

We consider the mechanism of photophoretic transport in protoplanetary disks that are optically thick to radiation. Here, photophoresis is not caused by the central star but by temperature fluctuations that subject suspended solid particles, including chondrules, to non-isotropic thermal radiation within the disk. These short-lived temperature fluctuations can explain time-of-flight size sorting and general number density enhancements. The same mechanism will also lead to velocity fluctuations of dust aggregates beyond 100ms−1 for mm-sized particles in protoplanetary disks. Applying this in future research will change our understanding of the early phases of collisional dust evolution and aggregate growth as particles cross the bouncing barrier and as mass transfer rates are altered.

Radiative Heating by Hot Planetesimals

A New Mechanism for Chondrule Formation: Radiative Heating by Hot Planetesimals

Authors:

Herbst et al

Abstract:

We propose that chondrules are formed by radiative heating of pre-existing dust clumps during close fly-bys of planetesimals with incandescent lava at their surfaces. We show that the required temperatures and cooling rates are easily achieved in this scenario and discuss how it is consistent with bulk aspects of chondritic meteorites, including complementarity and the co-mingling of FeO-poor and FeO-rich chondrules.

Chondrule Formation via Impact Jetting Triggered by Planetary Accretion

Chondrule Formation via Impact Jetting Triggered by Planetary Accretion

Authors:

Hasegawa et al

Abstract:

Chondrules are one of the most primitive elements that can serve as a fundamental clue as to the origin of our Solar system. We investigate a formation scenario of chondrules that involves planetesimal collisions and the resultant impact jetting. Planetesimal collisions are the main agent to regulate planetary accretion that corresponds to the formation of terrestrial planets and cores of gas giants. The key component of this scenario is that ejected materials can melt when the impact velocity between colliding planetesimals exceeds about 2.5 km s−1. The previous simulations show that the process is efficient enough to reproduce the primordial abundance of chondrules. We examine this scenario carefully by performing semi-analytical calculations that are developed based on the results of direct N-body simulations. As found by the previous work, we confirm that planetesimal collisions that occur during planetary accretion can play an important role in forming chondrules. This arises because protoplanet-planetesimal collisions can achieve the impact velocity of about 2.5 km s−1 or higher, as protoplanets approach the isolation mass (Mp,iso). Assuming that the ejected mass is a fraction (Fch) of colliding planetesimals' mass, we show that the resultant abundance of chondrules is formulated well by FchMp,iso, as long as the formation of protoplanets is completed within a given disk lifetime. We perform a parameter study and examine how the abundance of chondrules and their formation timing change. We find that the impact jetting scenario generally works reasonably well for a certain range of parameters, while more dedicated work would be needed to include other physical processes that are neglected in this work and to examine their effects on chondrule formation.

Chondrule Transport in Protoplanetary Disks

Chondrule Transport in Protoplanetary Disks

Authors:

Goldberg et al

Abstract:

Chondrule formation remains one of the most elusive early Solar System events. Here, we take the novel approach of employing numerical simulations to investigate chondrule origin beyond purely cosmochemical methods. We model the transport of generically-produced chondrules and dust in a 1D viscous protoplanetary disk model, in order to constrain the chondrule formation events. For a single formation event we are able to match analytical predictions of the memory chondrule and dust populations retain of each other (complementarity), finding that a large mass accretion rate (≳10−7~M⊙~yr−1) allows for delays on the order of the disk's viscous timescale between chondrule formation and chondrite accretion. Further, we find older disks to be severely diminished of chondrules, with accretion rates ≲10−9~M⊙~yr−1 for nominal parameters. We then characterize the distribution of chondrule origins in both space and time, as functions of disk parameters and chondrule formation rates, in runs with continuous chondrule formation and both static and evolving disks. Our data suggest that these can account for the observed diversity between distinct chondrite classes, if some diversity in accretion time is allowed for.