Did the Solar System form in a sequential triggered star formation event?

TL;DR

This paper evaluates whether the Solar System formed through sequential triggered star formation or direct supernova pollution, using simulations to analyze age distributions and triggering probabilities, ultimately questioning the likelihood of the triggered scenario.

Contribution

The study provides a detailed simulation-based analysis showing the improbability of sequential triggered star formation as the origin of the Solar System.

Findings

Sequential star formation results in large age spreads.

Triggered formation of spatially discrete star populations is highly unlikely.

Triggered star formation is as improbable as direct supernova pollution.

Abstract

The presence and abundance of the short-lived radioisotopes (SLRs) $^{26}$Al and $^{60}$Fe during the formation of the Solar System is difficult to explain unless the Sun formed in the vicinity of one or more massive star(s) that exploded as supernovae. Two different scenarios have been proposed to explain the delivery of SLRs to the protosolar nebula: (i) direct pollution of the protosolar disc by supernova ejecta and (ii) the formation of the Sun in a sequential star formation event in which supernovae shockwaves trigger further star formation which is enriched in SLRs. The sequentially triggered model has been suggested as being more astrophysically likely than the direct pollution scenario. In this paper we investigate this claim by analysing a combination of $N$-body and SPH simulations of star formation. We find that sequential star formation would result in large age spreads (or even bi-modal age distributions for spatially coincident events) due to the dynamical relaxation of the first star-formation event(s). Secondly, we discuss the probability of triggering spatially and temporally discrete populations of stars and find this to be only possible in very contrived situations. Taken together, these results suggest that the formation of the Solar System in a triggered star formation event is as improbable, if not more so, than the direct pollution of the protosolar disc by a supernova.