The travel diary of a micron-The travel diary of a micron-sized sphere, found in the sized sphere, found in the Murchison meteoriteMurchison meteorite

Timothy Joseph Volkert and P. FraundorfTimothy Joseph Volkert and P. FraundorfPhysics & Astronomy and Center for Molecular Physics & Astronomy and Center for Molecular ElectronicsElectronicsU. Of Missouri – StL (63121), St. Louis, MO, USAU. Of Missouri – StL (63121), St. Louis, MO, USA

Research GoalsResearch Goals

For just a few decades, astronomy For just a few decades, astronomy has had powerful new tools for has had powerful new tools for viewing the space around us.viewing the space around us.

Up-close-and-personal looks and first Up-close-and-personal looks and first hand knowledge of interstellar grains.hand knowledge of interstellar grains.

Ability to allow microscopic particles Ability to allow microscopic particles “in hand” to tell their story of travel “in hand” to tell their story of travel and originsand origins

OutlineOutline

Vivian the “onion”Vivian the “onion”

Unlayered graphene coreUnlayered graphene core

Graphitic layeringGraphitic layering

0.9 µm

Obtaining VivianObtaining Vivian

An example of An example of the microtome the microtome used to obtain used to obtain VivianVivian

Slices are less Slices are less than 100 than 100 nanometers thinnanometers thin

diamond knife

U. of Chicago immerses chunks of U. of Chicago immerses chunks of meteorite in acids/bases to dissolve meteorite in acids/bases to dissolve oxides, leaves behind graphitic oxides, leaves behind graphitic spherules and several nobles gases.spherules and several nobles gases.

Chicago group finds that the noble Chicago group finds that the noble gases (especially Ne, also Ar, Kr, and gases (especially Ne, also Ar, Kr, and Xe) found exist in exotic isotopic Xe) found exist in exotic isotopic abundances.abundances.

U. of Washington group find carbon U. of Washington group find carbon isotope ratios of C/ C far less than the isotope ratios of C/ C far less than the typical solar value of 89.typical solar value of 89.

Extraction from Extraction from MurchisonMurchison

12 13

22

Murchison’s TravelsMurchison’s Travels

Murchison impacted Murchison impacted near Murchison, near Murchison, Victoria in Australia Victoria in Australia on Sept. 28on Sept. 28thth, 1969 , 1969 in several pieces.in several pieces.

Nano-scale structure Nano-scale structure of the meteorite’s of the meteorite’s interior virtually interior virtually unchanged by unchanged by impact.impact.

Murchison was the Murchison was the perfect size to allow perfect size to allow entry without entry without burning up.burning up.

A chunk of the Murchison meteorite

Beginnings of Beginnings of MurchisonMurchison Radiometric dating of Murchison Radiometric dating of Murchison

puts its parent body’s formation at puts its parent body’s formation at 4.4 to 4.6 billion years ago, around 4.4 to 4.6 billion years ago, around the time of our Solar System’s the time of our Solar System’s formation.formation.

Vivian and her gang of particles Vivian and her gang of particles were swept up upon entering Sol’s were swept up upon entering Sol’s neighborhood from interstellar neighborhood from interstellar space.space.

Vivian’s YouthVivian’s Youth

Astrophysical Astrophysical observations suggest observations suggest galactic rotation on the galactic rotation on the order of once per order of once per 100,000 years, and 100,000 years, and Vivian may have spent Vivian may have spent well over 1 billion years well over 1 billion years in interstellar space.in interstellar space.

Vivian was found Vivian was found separate from her separate from her cohorts in Murchison, a cohorts in Murchison, a sign that she spent time sign that she spent time in interstellar travel in interstellar travel alone.alone.

Vivian’s InfancyVivian’s Infancy

During Vivian’s creation, she During Vivian’s creation, she underwent radiation pressure due to underwent radiation pressure due to fusion in her host AGB star’s core.fusion in her host AGB star’s core.

F = ma =L π r^2c 4 π R^2

m = π r^3 ρ43

Vivian’s Infancy (cont.)Vivian’s Infancy (cont.)

VivianCore density: 1.8 g/ccCore radius: 0.675 µm

3L16 π c ρ R^2 r

a =

Solving for acceleration gives us a value of 5 m/s^2, with an uncertainty of an order of magnitude in either direction.

DiscussionDiscussion

Carbon atoms in an AGB star’s atmosphere Carbon atoms in an AGB star’s atmosphere are most likely swept up by an outward are most likely swept up by an outward bound particle such as Vivian.bound particle such as Vivian.

This may follow indirect observations of This may follow indirect observations of stellar outflows in such stars, or even more stellar outflows in such stars, or even more exotic processes yet unknown.exotic processes yet unknown.

Pre-solar onion sizes and rim thickness Pre-solar onion sizes and rim thickness along with models of gas density and along with models of gas density and temperature in AGB stars could lead to temperature in AGB stars could lead to further investigations.further investigations.

Discussion (cont.)Discussion (cont.)

Vivian’s core growth, unique Vivian’s core growth, unique formation mechanismsformation mechanisms

Questions?Questions?