Interaction of Supernova Ejecta with Nearby Protoplanetary Disks

Abstract

The early solar system contained short-lived radionuclides such as 60 Fe (t 1/2 = 1.5 Myr) whose most likely source was a nearby supernova. Previous models of solar system formation considered a supernova shock that triggered the collapse of the Sun's nascent molecular cloud. We advocate an alternative hypothesis, that the solar system's protoplanetary disk had already formed when a very close (<1 pc) supernova injected radioactive material directly into the disk. We conduct the first numerical simulations designed to answer two questions related to this hypothesis: Will the disk be destroyed by such a close supernova, and will any of the ejecta be mixed into the disk? Our simulations demonstrate that the disk does not absorb enough momentum from the shock to escape the protostar to which it is bound. Only low amounts (<1%) of mass loss occur, due to stripping by Kelvin-Helmholtz instabilities across the top of the disk, which also mix into the disk about 1% of the intercepted ejecta. These low efficiencies of destruction and injection are due to the fact that the high disk pressures prevent the ejecta from penetrating far into the disk before stalling. Injection of gas-phase ejecta is too inefficient to be consistent with the abundances of radionuclides inferred from meteorites. On the other hand, the radionuclides found in meteorites would have condensed into dust grains in the supernova ejecta, and we argue that such grains will be injected directly into the disk with nearly 100% efficiency. The meteoritic abundances of the short-lived radionuclides such as 60 Fe therefore are consistent with injection of grains condensed from the ejecta of a nearby (<1 pc) supernova, into an already formed protoplanetary disk.

Solar system genealogy revealed by extinct short-lived radionuclides in meteorites

“…The shell mass agrees with observations (Zavagno et al 2007;Deharveng et al 2008) though it could be a factor of two higher (Zavagno et al 2007;Deharveng et al 2008). In any case, the assumed mass of the shell is 10 5 times higher than the disk of Ouellette et al (2005), 500 times more than the core of , and four times greater than the most massive bow-shock shell of Tatischeff et al (2010). It means that the probability of enrichment (not even taking the astrophysical context into account, Gounelle & Meibom 2008), for a given massive star, is far higher in our collect-injectionand-collapse model than in any other model, considering that a single massive star is responsible for the solar system's 26 Al.…”

“…It does not suffer from the other difficulties encountered by the previous models. Because the 60 Fe and 26 Al have a decoupled origin (SN and wind, respectively), our model is not faced with the problem of the low 26 Al/ 60 Fe ratio met by the single SN models (Ouellette et al 2005;. In addition, when the massive star goes SN, the disk is far enough away (5−10 pc) to avoid the disruption caused by the SN shockwave (Chevalier 2000) or overinjection of 60 Fe, unlike the model of Gaidos et al (2009).…”

“…Because the solar system abundance of 26 Al is far better constrained than that of 60 Fe, we use the former SLR (C [ 26 Al] = 3.3 ppb) to calculate the maximum distance at which the SN has to be from either the disk or the core to deliver SLRs at the solar abundance. Using the SN yields of massive stars with M ≤ 60 M (Huss et al 2009) calculated by Woosley & Heger (2007), we obtain r ≤ 0.4 pc for a disk of mass 0.013 M (Hayashi et al 1985;Ouellette et al 2005) and size r 0 = 100 AU with an injection efficiency of 0.7 (Ouellette et al 2009), and r ≤ 0.6 pc for a core of mass 2 M and size r 0 = 0.058 pc with an injection efficiency of 0.02 . The receiving phases parameters (mass and size) correspond to the observed properties of disks and cores adopted by the tenants of the single SN model (Ouellette et al 2005;, while the injection efficiencies are estimated by the same authors (Ouellette et al 2009;).…”

THE ELUSIVE60Fe IN THE SOLAR NEBULA

“…Finally, Buchwald (1975) indicates that if shock melting happened in Muonionalusta, it was of very short duration. 60 Fe may be produced either from a single supernova explosion with injection of 60 Fe into the protoplanetary disk (Ouellette et al 2007) or from the molecular cloud core progenitor (Cameron et al 1995) of our solar system. AGB stars can produce 60 Fe with 60 Fe/ 56 Fe ratios up to 10 −7 .…”

Stellar neutron capture rates and thesprocess

“…The enrichment of 60 Ni in meteoritic inclusions [35][36][37][38] indicates that 60 Fe has been present in substantial amounts in the early solar system and has been taken as evidence for early injection of 60 Fe from a nearby supernova into the protosolar nebula [39][40][41][42]. In this context, 60 Fe represents an important chronometer for the early solar system (ESS) [43].…”