The travel diary of a micron-sized sphere, found in the Murchison meteorite Timothy Joseph Volkert and P. Fraundorf Physics & Astronomy and Center for Molecular Electronics U. Of Missouri – StL (63121), St. Louis, MO, USA

Research Goals For just a few decades, astronomy has had powerful new tools for viewing the space around us. For just a few decades, astronomy has had powerful new tools for viewing the space around us. Up-close-and-personal looks and first hand knowledge of interstellar grains. Up-close-and-personal looks and first hand knowledge of interstellar grains. Ability to allow microscopic particles “in hand” to tell their story of travel and origins Ability to allow microscopic particles “in hand” to tell their story of travel and origins

Outline

Vivian the “onion” Unlayered graphene core Graphitic layering 0.9 µm

Obtaining Vivian An example of the microtome used to obtain Vivian An example of the microtome used to obtain Vivian Slices are less than 100 nanometers thin Slices are less than 100 nanometers thin diamond knife

U. of Chicago immerses chunks of meteorite in acids/bases to dissolve oxides, leaves behind graphitic spherules and several nobles gases. U. of Chicago immerses chunks of meteorite in acids/bases to dissolve oxides, leaves behind graphitic spherules and several nobles gases. Chicago group finds that the noble gases (especially Ne, also Ar, Kr, and Xe) found exist in exotic isotopic abundances. Chicago group finds that the noble gases (especially Ne, also Ar, Kr, and Xe) found exist in exotic isotopic abundances. U. of Washington group find carbon isotope ratios of C/ C far less than the typical solar value of 89. U. of Washington group find carbon isotope ratios of C/ C far less than the typical solar value of 89. Extraction from Murchison

Murchison’s Travels Murchison impacted near Murchison, Victoria in Australia on Sept. 28 th, 1969 in several pieces. Murchison impacted near Murchison, Victoria in Australia on Sept. 28 th, 1969 in several pieces. Nano-scale structure of the meteorite’s interior virtually unchanged by impact. Nano-scale structure of the meteorite’s interior virtually unchanged by impact. Murchison was the perfect size to allow entry without burning up. Murchison was the perfect size to allow entry without burning up. A chunk of the Murchison meteorite

Beginnings of Murchison Radiometric dating of Murchison puts its parent body’s formation at 4.4 to 4.6 billion years ago, around the time of our Solar System’s formation. Radiometric dating of Murchison puts its parent body’s formation at 4.4 to 4.6 billion years ago, around the time of our Solar System’s formation. Vivian and her gang of particles were swept up upon entering Sol’s neighborhood from interstellar space. Vivian and her gang of particles were swept up upon entering Sol’s neighborhood from interstellar space.

Vivian’s Youth Astrophysical observations suggest galactic rotation on the order of once per 100,000 years, and Vivian may have spent well over 1 billion years in interstellar space. Astrophysical observations suggest galactic rotation on the order of once per 100,000 years, and Vivian may have spent well over 1 billion years in interstellar space. Vivian was found separate from her cohorts in Murchison, a sign that she spent time in interstellar travel alone. Vivian was found separate from her cohorts in Murchison, a sign that she spent time in interstellar travel alone.

Vivian’s Infancy During Vivian’s creation, she underwent radiation pressure due to fusion in her host AGB star’s core. During Vivian’s creation, she underwent radiation pressure due to fusion in her host AGB star’s core. F = ma = L π r^2 c 4 π R^2 m = π r^3 ρ 4 3

Vivian’s Infancy (cont.) Vivian Core density: 1.8 g/cc Core radius: µm 3L 16 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.

Discussion Carbon atoms in an AGB star’s atmosphere are most likely swept up by an outward bound particle such as Vivian. Carbon atoms in an AGB star’s atmosphere are most likely swept up by an outward bound particle such as Vivian. This may follow indirect observations of stellar outflows in such stars, or even more exotic processes yet unknown. This may follow indirect observations of stellar outflows in such stars, or even more exotic processes yet unknown. Pre-solar onion sizes and rim thickness along with models of gas density and temperature in AGB stars could lead to further investigations. Pre-solar onion sizes and rim thickness along with models of gas density and temperature in AGB stars could lead to further investigations.

Discussion (cont.) Vivian’s core growth, unique formation mechanisms Vivian’s core growth, unique formation mechanisms Questions? Questions?