An interstellar origin for the beryllium 10 in calcium-rich, aluminum-rich inclusions

Steven Desch, Harold C. Connolly, G. Srinivasan

Research output: Contribution to journalArticle

81 Citations (Scopus)

Abstract

Beryllium 10 is a short-lived radionuclide (t1/2 = 1.5 Myr) that was incorporated live into calcium-rich, aluminum-rich inclusions (CAIs) at the birth of our solar system. Beryllium 10 is unique among the short-lived radionuclides in that it is formed only by spallation reactions and not by nucleosynthesis, e.g., in a supernova. Recent work by McKeegan, Gounelle, and others has stated that the high initial abundance of 10Be in CAIs (10Be/9Be ≈ 1 × 10-3) cannot be attributed to galactic cosmic rays (GCRs) and therefore concluded that the spallation reactions must have occurred within the solar nebula itself, because of energetic particles emitted by the early Sun. In this paper we reexamine this conclusion. We calculate the contributions of GCRs to the 10Be abundance in a molecular cloud core as it collapses to form a protostar and protoplanetary disk. We constrain the flux of protons and 10Be GCRs in the Sun's molecular cloud core 4.5 Gyr ago. We use numerical magneto-hydrodynamic simulations of star formation to model the time evolution of the magnetic field strength and column density of gas in a collapsing cloud core. We account for magnetic focusing and magnetic mirroring and the anisotropic distribution of GCR pitch angles in the cloud core. We calculate the rates at which GCR protons and α-particles induce spallation reactions producing 10Be atoms, and the rates at which GCR 10Be nuclei are trapped in the cloud core. Accounting also for the decay of 10Be over the evolution of the cloud core, we calculate the time-varying 10Be/9Be ratio. We find that at the time of protostar formation 10Be/9Be ≈ 1 × 10 -3, with an uncertainty of about a factor of 3. Spallation reactions account for 20% of the 10Be in CAIs, while trapped GCR 10Be nuclei account for the other 80%. The initial abundance of 10Be in CAIs is therefore entirely attributable to cosmic rays. We discuss the implications of this finding for the origin of other short-lived radionuclides and for the use of 10Be as a chronometer.

Original languageEnglish (US)
Pages (from-to)528-542
Number of pages15
JournalAstrophysical Journal
Volume602
Issue number1 I
DOIs
StatePublished - Feb 10 2004

Fingerprint

beryllium 10
beryllium isotope
cosmic ray
calcium
aluminum
inclusions
spallation
radioactive isotopes
protostars
radionuclide
molecular clouds
chronometers
solar nebula
nuclei
magnetohydrodynamic simulation
protoplanetary disks
protons
pitch (inclination)
energetic particles
nuclear fusion

Keywords

  • Cosmic rays
  • Nuclear reactions, nucleosynthesis, abundances
  • Solar system: formation
  • Stars: formation

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

An interstellar origin for the beryllium 10 in calcium-rich, aluminum-rich inclusions. / Desch, Steven; Connolly, Harold C.; Srinivasan, G.

In: Astrophysical Journal, Vol. 602, No. 1 I, 10.02.2004, p. 528-542.

Research output: Contribution to journalArticle

Desch, Steven ; Connolly, Harold C. ; Srinivasan, G. / An interstellar origin for the beryllium 10 in calcium-rich, aluminum-rich inclusions. In: Astrophysical Journal. 2004 ; Vol. 602, No. 1 I. pp. 528-542.
@article{358f26d64e794cf6a5ec3ecc79840398,
title = "An interstellar origin for the beryllium 10 in calcium-rich, aluminum-rich inclusions",
abstract = "Beryllium 10 is a short-lived radionuclide (t1/2 = 1.5 Myr) that was incorporated live into calcium-rich, aluminum-rich inclusions (CAIs) at the birth of our solar system. Beryllium 10 is unique among the short-lived radionuclides in that it is formed only by spallation reactions and not by nucleosynthesis, e.g., in a supernova. Recent work by McKeegan, Gounelle, and others has stated that the high initial abundance of 10Be in CAIs (10Be/9Be ≈ 1 × 10-3) cannot be attributed to galactic cosmic rays (GCRs) and therefore concluded that the spallation reactions must have occurred within the solar nebula itself, because of energetic particles emitted by the early Sun. In this paper we reexamine this conclusion. We calculate the contributions of GCRs to the 10Be abundance in a molecular cloud core as it collapses to form a protostar and protoplanetary disk. We constrain the flux of protons and 10Be GCRs in the Sun's molecular cloud core 4.5 Gyr ago. We use numerical magneto-hydrodynamic simulations of star formation to model the time evolution of the magnetic field strength and column density of gas in a collapsing cloud core. We account for magnetic focusing and magnetic mirroring and the anisotropic distribution of GCR pitch angles in the cloud core. We calculate the rates at which GCR protons and α-particles induce spallation reactions producing 10Be atoms, and the rates at which GCR 10Be nuclei are trapped in the cloud core. Accounting also for the decay of 10Be over the evolution of the cloud core, we calculate the time-varying 10Be/9Be ratio. We find that at the time of protostar formation 10Be/9Be ≈ 1 × 10 -3, with an uncertainty of about a factor of 3. Spallation reactions account for 20{\%} of the 10Be in CAIs, while trapped GCR 10Be nuclei account for the other 80{\%}. The initial abundance of 10Be in CAIs is therefore entirely attributable to cosmic rays. We discuss the implications of this finding for the origin of other short-lived radionuclides and for the use of 10Be as a chronometer.",
keywords = "Cosmic rays, Nuclear reactions, nucleosynthesis, abundances, Solar system: formation, Stars: formation",
author = "Steven Desch and Connolly, {Harold C.} and G. Srinivasan",
year = "2004",
month = "2",
day = "10",
doi = "10.1086/380831",
language = "English (US)",
volume = "602",
pages = "528--542",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1 I",

}

TY - JOUR

T1 - An interstellar origin for the beryllium 10 in calcium-rich, aluminum-rich inclusions

AU - Desch, Steven

AU - Connolly, Harold C.

AU - Srinivasan, G.

PY - 2004/2/10

Y1 - 2004/2/10

N2 - Beryllium 10 is a short-lived radionuclide (t1/2 = 1.5 Myr) that was incorporated live into calcium-rich, aluminum-rich inclusions (CAIs) at the birth of our solar system. Beryllium 10 is unique among the short-lived radionuclides in that it is formed only by spallation reactions and not by nucleosynthesis, e.g., in a supernova. Recent work by McKeegan, Gounelle, and others has stated that the high initial abundance of 10Be in CAIs (10Be/9Be ≈ 1 × 10-3) cannot be attributed to galactic cosmic rays (GCRs) and therefore concluded that the spallation reactions must have occurred within the solar nebula itself, because of energetic particles emitted by the early Sun. In this paper we reexamine this conclusion. We calculate the contributions of GCRs to the 10Be abundance in a molecular cloud core as it collapses to form a protostar and protoplanetary disk. We constrain the flux of protons and 10Be GCRs in the Sun's molecular cloud core 4.5 Gyr ago. We use numerical magneto-hydrodynamic simulations of star formation to model the time evolution of the magnetic field strength and column density of gas in a collapsing cloud core. We account for magnetic focusing and magnetic mirroring and the anisotropic distribution of GCR pitch angles in the cloud core. We calculate the rates at which GCR protons and α-particles induce spallation reactions producing 10Be atoms, and the rates at which GCR 10Be nuclei are trapped in the cloud core. Accounting also for the decay of 10Be over the evolution of the cloud core, we calculate the time-varying 10Be/9Be ratio. We find that at the time of protostar formation 10Be/9Be ≈ 1 × 10 -3, with an uncertainty of about a factor of 3. Spallation reactions account for 20% of the 10Be in CAIs, while trapped GCR 10Be nuclei account for the other 80%. The initial abundance of 10Be in CAIs is therefore entirely attributable to cosmic rays. We discuss the implications of this finding for the origin of other short-lived radionuclides and for the use of 10Be as a chronometer.

AB - Beryllium 10 is a short-lived radionuclide (t1/2 = 1.5 Myr) that was incorporated live into calcium-rich, aluminum-rich inclusions (CAIs) at the birth of our solar system. Beryllium 10 is unique among the short-lived radionuclides in that it is formed only by spallation reactions and not by nucleosynthesis, e.g., in a supernova. Recent work by McKeegan, Gounelle, and others has stated that the high initial abundance of 10Be in CAIs (10Be/9Be ≈ 1 × 10-3) cannot be attributed to galactic cosmic rays (GCRs) and therefore concluded that the spallation reactions must have occurred within the solar nebula itself, because of energetic particles emitted by the early Sun. In this paper we reexamine this conclusion. We calculate the contributions of GCRs to the 10Be abundance in a molecular cloud core as it collapses to form a protostar and protoplanetary disk. We constrain the flux of protons and 10Be GCRs in the Sun's molecular cloud core 4.5 Gyr ago. We use numerical magneto-hydrodynamic simulations of star formation to model the time evolution of the magnetic field strength and column density of gas in a collapsing cloud core. We account for magnetic focusing and magnetic mirroring and the anisotropic distribution of GCR pitch angles in the cloud core. We calculate the rates at which GCR protons and α-particles induce spallation reactions producing 10Be atoms, and the rates at which GCR 10Be nuclei are trapped in the cloud core. Accounting also for the decay of 10Be over the evolution of the cloud core, we calculate the time-varying 10Be/9Be ratio. We find that at the time of protostar formation 10Be/9Be ≈ 1 × 10 -3, with an uncertainty of about a factor of 3. Spallation reactions account for 20% of the 10Be in CAIs, while trapped GCR 10Be nuclei account for the other 80%. The initial abundance of 10Be in CAIs is therefore entirely attributable to cosmic rays. We discuss the implications of this finding for the origin of other short-lived radionuclides and for the use of 10Be as a chronometer.

KW - Cosmic rays

KW - Nuclear reactions, nucleosynthesis, abundances

KW - Solar system: formation

KW - Stars: formation

UR - http://www.scopus.com/inward/record.url?scp=1842535487&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=1842535487&partnerID=8YFLogxK

U2 - 10.1086/380831

DO - 10.1086/380831

M3 - Article

AN - SCOPUS:1842535487

VL - 602

SP - 528

EP - 542

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 I

ER -