- Presolar grains are microscopic dust particles that formed in stars before the solar system. They are found in meteorites and provide insights into stellar and nucleosynthetic processes. - Two main approaches to study presolar grains are chemical separation from meteorites and in situ search using ion imaging techniques. Chemical separation risks altering grains while in situ search is time-consuming but preserves grain morphology. - Grains show isotopic anomalies reflecting their origins in AGB stars, supernovae, novae, and provide information about dust formation conditions in different stellar environments and the presolar molecular cloud.

1. Presolar Grains: Starbits in Laboratory
Lalit Kumar Shukla
(lalit@prl.res.in)
PSDN,PRL
1

2. Introduction
Different approaches and their pros & cons
Chemical Separation
Analysing tools
Classification
Stellar Sources
Future Plan
Outline
2

3. Presolar Grains:
chondrites
Presolar grains are
identified from their
isotopic anomalies
which can not be
explained by any
process occurring
within solar system.
3

4. Why do we study Presolar Grains?
Chemical and isotopic signatures record
grain formation and nucleosynthetic
processes of various stars.
Morphologies and compositions may
reflect grain formation conditions in
stellar environments.
Provide a glimpse into dust population
that accumulated in the presolar
molecular cloud.
4

5. Presolar Grains
(found in crystalline as well as amorphous phase)
Carbide Grains Nitride Grains Oxide Grains Silicate Grains
Diamond Silicon Carbide Graphite
Silicon Nitride
Corundum
(Al2O3)
Spinel
(MgAl2O4)
Hibonite
Pyroxene Olivine
(Size = 0.002μm) (Size = 0.2-50 μm) (Size = 1-20μm)
(Size = <1μm)
(Size = 0.2-50 μm) (Size = < 0.5 μm)
((Ca,Ce)(Al,Ti,Mg)12O19)
SS: Sne? SS: AGB, SNe
SS: SNe
SS: RGB, AGB, Sne, Novae SS: RGB, AGB, SNe
SS: AGB, J star, Sne, Novae
SS: Stellar Source, SNe: core-collapsed supernovae, AGB: Asymptotic Branch Star, RGB: Red Giant Branch Star, J
star: J-type carbon star
5

6. Picture Book of Presolar Grains
6

7. Abundance of different types of presolar grains:
 Reported maximum values from different meteorites.
7

8. Size Distribution of Presolar Grains
 Varies from meteorite to meteorite
(Amari et al. 1994, Huss et al. 1997)
 Variations in isotopic properties are
seen with grain size (Lewis et al. 1994)
Data is taken from Washington University Presolar Grain Database
8

9. Approaches to Study
Chemical Separation:
Separated from meteorites
by progressively harsher
acid dissolution.
In situ Search:
Identified by multi-
detection raster ion imaging
by NanoSIMS.
9

10. O isotopic images of 10 µm x 10 µm area
Isotope distribution images acquired
by rastering the primary ion beam over
sample.
Image resolution is determined to the
first order by the primary ion beam
diameter.
From isotope distribution maps
isotope ratio images can be calculated
which makes it possible to search for
object with specific fingerprint.
16O
17O
δ17O
In situ Search Approach
10

11. Comparison of both approaches
Chemical Separation In situ search
 Some presolar phases get dissolve
(silicates, amorphous grains, less
refractory coating around grains
etc.).
 May alter surfaces of grains
chemically and/or isotopically.
 Not great sampling issue
(Abundance calculation?)
 Time taking sample preparation.
But once over, thousands grains are
ready for analysis.
 No dilution effect.
 All phases can be recovered (no
chemistry).
 Grain morphologies remain
unchanged.
 Sampling matters (Abundance
calculation?)
 Finding grains take quite time.
 Dilution effect (?)
11

12. Murray Murchison
Details Date of Fall: 20/09/1950
Location: Kentucky, USA
Weight: 12.6 Kg
Class: CM2, Carbonaceous
Chondrite
Date of Fall: 28/09/1969
Location: Victoria, Australia
Weight: 100 Kg
Class: CM2, Carbonaceous Chondrite
PSGs
Reported
SiC: Heck ApJ 2007, ..
Spinel: Gyngard ApJ 2007, ..
Corundum : Zinner GCA 2003, ..
SiC: 19 ppm (Devidson J. LPSC 2009)
Graphite: Amari GCA 1994, ..
Spinel: Nittler MetSoc 2007, ..
Corundum: Zinner GCA 2003, ..
Silicates: 3 ppm (Nagashima K., LPSC 2005)
Bulk
Chemical
Compositio
n
(wt.%)
SiO2 (28.69), Al2O3 (2.19), FeO
(21.08), MgO (19.77), CaO (1.92),
FeS(7.67), C (2.78) ,…
Wiik H. B. (1956), GCA 9,279-289
(Source: MetBase)
SiO2 (29.07), Al2O3 (2.15), FeO (22.39), MgO
(19.94), CaO (1.89), FeS(7.24), C (1.85) ,…
Jarosewich E.(1971), Meteoritics 6, 49-52
(Source: MetBase) 12

13. HF (10M) + HCl (1M)
Decant Solution)
HCl (6M)
Decant Solution)
Murray PM
17.82 g
PM +
HF(10M) + HCl(1M) (Five Changes)
HCl(6M) (Five Changes)
To dissolve silicates and metals
(at room temperature)
PM +
HF(10M) + HCl(1M) (Seven Changes)
HCl(6M) (Seven Changes)
To dissolve silicates and metals
(at 60oC)
PM +
H3BO3(0.6M) + HCl(6M) (Seven Changes)
HF(2M) + HCl(6M) (Seven Changes)
To dissolve fluorides and silicates
(at 55oC)
Wash with 0.1 M HCl
SiO2 + 4 HF → SiF4(g) + 2 H2O
FeS + 2HCl → FeCl2 + H2S (g)
FeO + 2HCl → FeCl2 + H2O
Yellowish color due to FeCl2 reduced as proceed
Chemical Separation of PSGs from Murray Meteorites
13
Received from Smithsonian
National Museum of Natural
History, Washington DC

14. Murchison MA
12 g
MA +
HF(10M) + HCl(1M) (Six Changes)
HCl(6M) (Five Changes)
To dissolve silicates and metals
(at room temperature)
MA +
HF(10M) + HCl(1M) (Four Changes)
HCl(6M) (Three Changes)
To dissolve silicates and metals
(at 60oC)
MA +
H3BO3(0.6M) + HCl(6M) (Seven Changes)
HF(2M) + HCl(6M) (Seven Changes)
To dissolve fluorides and silicates
(at 55oC)
Wash with 0.1 M HCl
Check in SEM for Silicates
MA1
MA1
MA1 + 4M KOH (at 70oC)
MA1 + 30% H2O2 (Below 20oC)
But temperature reached 30oC….
Chemical Separation of PSGs from Murchison Meteorite:
To remove
sulfur &
kerogen

15. YM (Residue)
0.30 g
YM +
Na2Cr2O7 (0.5N) + H2SO4 (2N)
at 85oC for 24h
NH3 treatment
YM1 + HClO4
at 200oC for 2h
YM2 + H2SO4
at 180oC for 4h
Wash with 0.1 M NaOH
To remove any reactive kerogen
that had survived the H2O2 treatment
To extract diamond
To destroy graphite and Organic C
To dissolve spinel and chromite
15

16. Analysing Tools:
Scanning Electron Microscope (SEM):
Grain morphology & composition
Transmission Electron Microscope (TEM):
Structural information
Ion Imaging Techniques:
To locate PSGs
Ion Probe Techniques:
For abundance & Isotopic measurement
16

17. Ion Probe Technique: Secondary Ion Mass Spectrometer
Sputtering of a small localized
area of solid sample by an
energetic primary ion beam under
high vacuum conditions to
generate energetic secondary ions
from sample surface that are mass
analyzed.
Basic Principle:
Non-destructive technique
Less sample preparation is needed
Element H to U may be detected
Isotopic ratios can be measured precisely in very localised area
Advantages:
Matrix Dependent
Sample must be vacuum Compatible
Limitations:
17

18. Why NanoSIMS?
High spatial resolution: ( ~ 50 nm for Cs+
and ~200 nm for O-) Capable of analyzing
sub micrometer-sized presolar grains.
High mass resolution: Interferences can be
resolved with MRP (m/Δm) = 10,000 to
15,000.
High Transmission: ~ 30 x IMS-4f
Multi isotope (5) detection facility: Made
in-situ search for presolar grains possible.
Less destructive technique: Few Ao.
Really needed for such precious grains!
18

19. Classification of Presolar Grains on the basis of Isotopic Data
Data is taken from Washington University Presolar Grain Database
Carbon and Nitrogen isotopic data:
19
Why Isotopic Abundances?
Formation of 12C:
α +α → 8Be + α → 12C
Formation of 13C:
12C(p, γ)13N(β+)13C
Completely different process!!
Formation of 14N:
13C(p,γ)14N
Formation of 15N:
14N(p,γ)15O(β+)15N
18O(p,α)15N

20. Classification of Presolar Grains on the basis of Isotopic Data
Oxygen Isotopic Data
Data is taken from Washington University Presolar Grain Database
20
Formation of 16O:
12C(α,γ)16O
Formation of 17O:
16O(p, γ)17F(β+)17O
Formation of 18O:
14N(α, γ)18F(β+)18O

21. Classification of Presolar Grains on the basis of Isotopic Data
Silicon Isotopic Data:
Data is taken from Washington University Presolar Grain Database21
Formation of 28Si:
16O+16O →28Si+ α
24Mg(α, γ) 28Si
Formation of 29Si:
28Si(n,γ)29Si
25Mg(α, γ)29Si
Formation of 30Si:
28Si(n,γ)29Si(n, γ)30Si
26Mg(α, γ)30Si

22. Stellar
Sources of
Presolar
Grains
22

23. AGB Stars
Characterized by an inert carbon-
oxygen core, surrounded by two
separate nuclear burning layers - an
inner layer of Helium and an outer
layer of Hydrogen. These layers are in
turn surrounded by a strongly
convective outer envelope.
All stars with masses 0.8 - 8 M
go through the AGB phase.
S-process nucleosynthesis:
Neutron Density: Nn ~ 107 n/cm3
τ (n capture) >> τ (β- decay)
Neutron source for AGB stars:
1. 12C(p, γ)13N(β+ν)13C(α, n)16O (Low Mass (0.8-2.5 M) AGB Star)
2. 14N(α, γ)18F(β+)18O(α, γ)22Ne(α, n)25Mg (Intermediate mass (2.5-8 M)AGB star) 23

24. Gains from AGB Stars:
 About 90% Silicon Carbide
grains and large fraction of Oxide
and Silicate grains show the
signature of AGB star origin.
 Characterized by lower 12C/13C
and higher 14N/15N than solar,
enriched in 17O.
Hoppe et al, 1994
Lambert et al, 1986
12C/13C
1 10 100 1000 10000
14N/15N
10
100
1000
10000
Presolar SiC
Mainstream Grain
AB Grain
X Grain
Y Grain
Z Grain
Nova Grain
18O/16O
0.000 0.002 0.004 0.006
17O/16O
0.000
0.001
0.002
0.003
0.004
0.005
0.006
Presolar Silicate and Oxide grains
Group 1
Group 2
Group 3
Group 4
Data is taken from Washington University Presolar Grain Database
24

25. Supernovae
Core-collapse Supernovae
The catastrophic explosions of massive
stars (> 8 M)
R-process Nucleosynthesis:
Creates neutron-rich heavy isotopes
Neutron Density: Nn ~ 1023 n/cm3
τ (n capture) << τ (β- decay)
Fe core collapse leads to co-existence of heavy nuclei , α, p, n, e-, ν
p + e- → n + γ : leads to neutron rich matter
25
Figure courtesy of C. Winteler
Schematic stellar structure of massive stars before their death

26. Gains from Supernovae:
 Oxides(Group 4) , SiC type X, Si3N4 and low density graphite
grains
 Characterized by excess in 28Si, 18O and lower 14N/15N than
air, 12C/13C ~ 3.4-7200.
Presolar Graphite
12
C/13
C
1 10 100 1000 10000
14
N/15
N
1
10
100
1000
10000
High Density
Low Density
18O/16O
0.000 0.002 0.004 0.006
17O/16O
0.000
0.001
0.002
0.003
0.004
0.005
0.006
Presolar Silicate and Oxide grains
Group 1
Group 2
Group 3
Group 4
12C/13C
0 100 200 300 400 500 600
14N/15N
0
50
100
150
200
250
300
Presolar SiN Grains
Data is taken from Washington University Presolar Grain Database
26

27. Novae
In a nova, one star is a normal star and the
other star is a white dwarf. Matter accretes in a
thin layer on the surface of the white dwarf and
eventually ignites in a thermonuclear explosion
Nucleosynthesis is driven by p-capture
reactions and β+ -decays.
27

28. Gains from Novae:
 Isotopic peculiarities:13C, 14C, 18O, 22Na, 26Al, 30Si
 SiC from Novae: LOW 12C/13C & 14N/15N and HIGH 30Si/28Si
 O-rich Novae grains: 17O/16O > 4.4 x 10-3 & δ25Mg/24Mg up to 1000 ‰
Very few
Nova grains
are found
till date!!
12C/13C
1 10 100 1000 10000
14N/15N
10
100
1000
10000
Presolar SiC
Mainstream Grain
AB Grain
X Grain
Y Grain
Z Grain
Nova Grain
Data is taken from Washington University Presolar Grain Database
28

29. Future Plans
 Successful chemical Separation and in-situ search of PSGs from different
meteorites to compare both approaches and estimate laboratory loss.
 Investigation for the crystalline and amorphous phases in PSGs to understand
stellar environment.
 C, N, Si and O isotopic analysis of grains to search for nova candidates and
nucleosynthesis processes.
 Heavy element analysis to better understand nucleosynthesis in different stars
and mixing.
29

30. 30

31. Supplementary Slides
31

32. 32

33. 33

34. 34

35. 35
S- process R-process
Neutron capture time
is much larger than β-
decay lifetime
Neutron capture times
(10-3
to 10-4 s) are shorter
than β- decay lifetimes
Synthesized elements
closely follow the line
of β stability
Synthesized elements
lie away from the line
of β stability

36. Meteorites
DifferentiatedUndifferentiated
Chondrites
Achondrites Stony-Iron Iron
Pallasites Mesosiderites
IA IIA IIB IIIA IIIB VIA Other
Carbonaceous
CI
CH
CR
CK
CV
CO
CM
Ordinary
H
L
LL
Enstatites
EH
EL
R-Chondrites
Primitive
Martian Met. Moon Met. Other
36

37. Designation Mainstream X Y Z A+B Nova
12C/13C 10-100 20-7000 140-260 8-180 <3.5(A) 3.5-
10(B)
<10
14N/15N 50-2x104 10-180 400-5000 1100-1.9x104 40-1.2x104 <20
29Si/28Si 0.95-1.20x 28Si-rich 0.95-1.15 ~solar 1.20x ~solar
30Si/28Si 0.95-1.14x 28Si-rich 30Si-rich 30Si-rich 1.13x 30Si-rich
26Al/27Al 10-3 – 10-4 0.02-0.6 10-3 – 10-4 10-3 – 10-4 <0.06 Up to 0.4
Heavy trace
element
~10-20x Highly
depleted
~10x NA Solar or
10-20x
NA
22Ne Yes NA NA NA NA NA
Other isotopic
markers
Excess in 46Ti,
49Ti, 50Ti over
48Ti.
44Ca excess
41K excess
Excess in
46Ti, 49Ti, 50Ti
over 48Ti.
Excess in 46Ti,
49Ti, 50Ti over
48Ti.
Excess in
46Ti, 49Ti, 50Ti
over 48Ti.
47Ti-rich
Abundance 87-94% 1% 1-2% 0-3% 2-5% <<1%
Stellar Source AGB (1.5-3
Solar Mass)
SN II J-type C Star Novae
Hoppe and Ott, 1997 37

38. Designation Group I Group II Group III Group IV
17O/16O (0.45-2.9)x10-3 (0.55-1.4)x10-3 (1.9-4.15)x10-4 (5.2-98)x10-4
18O/16O (0.89-2.2)x10-3 ≤7.1x10-4 (0.65-1.9)x10-3 (3.1-6.1)x10-3
Mean initial
26Al/27Al
0.0023 0.0060 0.0004 0.0021
38

39. Scanning Electron Microscope:
Uses a focused beam of high-energy
electrons to generate a variety of
signals at the surface of solid
specimens.
The signals that derive from
electron-sample interactions reveal
information about the sample
including external morphology
(texture), chemical composition, and
orientation of materials making up
the sample.
39

40. Transmission Electron Microscope:
The scattering processes experienced by
electrons during their passage through the
specimen determine the kind of
information obtained.
Elastic scattering involves no energy loss
and gives rise to diffraction patterns.
Inelastic interactions at heterogeneities
such as grain boundaries, dislocations,
second phase particles, defects, density
variations, etc., cause complex absorption
and scattering effects, leading to a spatial
variation in the intensity of the
transmitted electrons.
40

41. HF-HCl
HCl
KOH
H2O2, NH3
Cr2O7
=
Density Separation
Size Separation
HClO4
H2SO4
NaOHHClO4
Size SeparationDensity Separation
Size Separation Size Separation Size Separation
g/ml
g/ml
µm
µm
KC2= Diamond
KJ = SiC
KE1, KFA1, KFB1, KFC1 = Graphite
Amari S. et. al 1994
Procedure developed for Chemical Separation of PSGs
41

42. 42

43. ♣ Isotopically anomalous noble gases were found in meteorites in late 60s.
Ne-E(L): 20Ne/22Ne < 0.01
(Solar 20Ne/22Ne = 9.8)
close to pure 22Ne (Black & Pepin)
♣ The huge isotopic anomalies in noble gases could be best explained by
nucleosynthesis in stars, not by processes occurring in the solar system.
⇓
Stardust hidden in meteorites?
♣ Effort to isolate carriers of anomalous noble gases
(Edward Anders, Roy S. Lewis and their co-workers)
Difficulties
Abundances of the carriers are low ( <0.01%).
They are small (a few μm or less).
Anomalous noble gases served as tracers to isolate these minerals.
“Burn the haystack to find a needle” (Edward Anders)
43

44. 44

45. 45
Stellar Nucleosynthesis: most important reactions
Hydrogen Burning: Deuterium burning, PP chain, CNO cycle
Helium Burning: Triple alpha process, Alpha process
Burning of heavier elements: lithium burning, carbon burning, neon burning, oxygen
burning, silicon burning.
Production of element heavier than iron: Neutron capture, proton capture, photo-
disintigration
Typical reactions relevant to astrophysics are:
H-burning in the Big Bang (T ~109 K, kT ~ 0.1 MeV) and in stars (107 K < T < 108 K, 1
keV < kT < 10 keV).
 He-burning in stars (T ~ 108 K, kT ~ 10 keV).
 C-, Ne-, O-burning in stars (108 K < T < 109 K, 10 keV < kT < 0.1MeV).
 Si-burning, hydrostatically near 109 K (0.1 MeV) and explosively at several times 109
K.
 Neutron capture in the Big Bang, s-process (a few ×108 K) and r-process (a few × 109
K).
 Spallation reactions, especially those involving cosmic rays in the ISM (non-thermal,
with MeV to GeV energies). Spallation reactions are those in which one or a few
nucleons are split off from a nucleus

46. 46

47. 47

48. 48

49. 49
Average nuclear binding energy per nucleon of stable isotopes (data: Audi et al. 2003)

50. 50
Solar system abundances of Asplund et al. (2005) with silicon normalised to 106

51. 51
The s-process path (red dashed line) in a section of the nuclear chart (proton
vs. neutron number) starting with iron as the seed of the slow neutron capture
process. The isotopes shown are either stable or unstable but long-living (red
squares). Figure adopted from K•appeler et al. (1989).

52. 52
The change in abundance Y of an isotope with mass A, due to neutron
captures and decays, is
λn(A) = neutron capture rate = σνT Nn
λβ(A) = beta decay rate
νT = Thermal neutron velocity = √ (2KT/mn )
Nn = Neutron density
σ = Neutron capture cross section

53. 53