Cosmochemical Consequences of Particle Trajectories During FU Orionis Outbursts by the Early Sun

TL;DR

This study models particle trajectories during FU Orionis outbursts in the early solar nebula, explaining the presence of refractory particles in comets and their isotopic variations, with implications for the formation of CAIs.

Contribution

First calculations of particle trajectories during FU Orionis outbursts showing how particles are transported and modified in the early solar system.

Findings

Particles of 0.1 to 10 cm traverse over 10 AU in less than 200 years.

Refractory particles acquire rims with variable oxygen isotope ratios.

Most CAIs formed during the final FU Orionis outbursts period.

Abstract

The solar nebula is thought to have undergone a number of episodes of FU Orionis outbursts during its early evolution. We present here the first calculations of the trajectories of particles in a marginally gravitationally unstable solar nebula during an FU Orionis outburst, which show that 0.1 to 10 cm-sized particles traverse radial distances of 10 AU or more, inward and outward, in less than 200 yrs, exposing the particles to temperatures from $\sim$ 60 K to $\sim$ 1500 K. Such trajectories can thus account for the discovery of refractory particles in comets. Refractory particles should acquire Wark-Lovering-like rims as they leave the highest temperature regions of the disk, and these rims should have significant variations in their stable oxygen isotope ratios. Particles are likely to be heavily modified or destroyed if they pass within 1 AU of the Sun, and so are only likely to survive if they formed in the final few FU Orionis outbursts, or were transported to the outer reaches of the solar system. Calcium, aluminum-rich inclusions (CAIs) from primitive meteorites are the oldest known solar system objects and have a very narrow age range. Most CAIs may have formed at the end of the FU Orionis outbursts phase, with an age range reflecting the period between the last few outbursts.