Studying Stardust with a Microscope Thomas Zega Es Are in the Proportion of Forms ABOUT the SCIENTIST SPECIAL to the ARIZONA DAILY STAR of Elements Called Isotopes

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1166 • UUNIVERSITYNIVERSITY O OFF A ARIZONARIZONA COLLEGECOLLEGE O OFF S SCIENCECIENCE SSunday,unday, NovemberNovember 30,30, 20142014 / A ARIZONARIZONA D DAILYAILY S STARTAR

DEPARTMENT OF PLANETARY SCIENCES/LUNAR AND PLANETARY LABORATORY Studying stardust with a microscope Thomas Zega es are in the proportion of forms ABOUT THE SCIENTIST SPECIAL TO THE ARIZONA DAILY STAR of elements called isotopes. My When people think of astron- colleagues and I use an instru- Thomas Zega is omy, they often picture scien- ment called a secondary ion a University of tists using telescopes such as mass spectrometer to probe the Arizona assistant the Large Binocular Telescope composition of meteorite pieces professor in the on Mt. Graham to examine the as small as 50 nanometers (1 nm Lunar and Plan- light emitted by stars outside = 0.000000001 meters). If the etary Laboratory the solar system. dust speck has the right isotopic and principal Scientists use measurements composition, we know we have a investigator of from such telescopes to glean piece of stardust. the Planetary Materials Research a wealth of information about By comparing the stardust Group. The group’s research focuses a star, including what stage it grain’s composition to theoreti- on understanding the chemistry of the is in its lifecycle, its size and its cal predictions, we can infer the early solar system and ancient stars chemical makeup. kind of star the grain came from, and surface processes on the moon Astronomers must make such its mass, its evolutionary state, and asteroids. He uses advanced elec- measurements remotely because and its bulk chemical makeup. tron and ion microscopy techniques they can’t visit a star to extract a Once we know the meteor- to probe the structural and chemical sample of it. ite contains stardust, we probe makeup of extraterrestrial materials to But there are ways to get a deeper. Using a focused-ion- gain insight into our origins. piece of a star and study it in the beam scanning-electron micro- laboratory. That’s what I do — I scope, we take one microscop- study pieces of ancient stardust. ically thin slice from a grain of EXPERIENCE SCIENCE But instead of using a telescope, stardust. I use a microscope to look for We then look at the slice with • UA Planetary Materials Re- stardust inside meteorites. a transmission electron micro- search Group: www.lpl.arizona. Over their lifetimes, stars scope to see the atomic struc- edu/PMRG/index.html shed matter that can condense ture and to learn more detailed PHOTOS BY THOMAS ZEGA / UA LUNAR AND PLANETARY LABORATORY / • UA Lunar and Planetary Labo- into solid mineral grains — star- chemistry. With that informa- FROM THE ASTROPHYSICAL JOURNAL, REPRODUCED BY PERMISSION OF THE AAS ratory: www.lpl.arizona.edu dust — if conditions are just tion, we determine how and un- This scanning electron microscope image shows a ﬂake of stardust lying right. der what pressure and tempera- atop a tiny gold pedestal. The stardust grain, just 1.5 micrometers wide by The grains can be transport- ture conditions the solid dust 2.5 micrometers long, came from an asymptotic giant branch star. ed for millions of years through grains formed around their host These the interstellar medium and be stars. incorporated into newly forming Figuring out how the grains stellar systems such as our own formed and their structure stardust solar system. sometimes helps us learn how Primitive meteorites, solid the stardust traveled through grains relics left over from our solar interstellar space before be- system’s birth, have continual- ing injected into our part of the ly rained down on Earth over its Milky Way galaxy 4.5 billion are quite 4-billion-year history. years ago. To ﬁnd bits of stardust, my Our laboratory studies of literally the colleagues and I examine the stardust provide direct informa- chemical composition of such tion on the workings of stellar building meteorites. We are looking for interiors and their gaseous en- evidence of the process through velopes. which atomic nuclei are fused These stardust grains are quite blocks of together–aprocessthat occurs literally the building blocks of inside stars. our solar system. They are what our solar Material from long-ago stars was around in our local part of has a different chemical compo- the Milky Way before the plan- If a human could see down to the atomic level, this is what a grain of star- sition from material formed in ets and the sun formed. dust would look like. This transmission electron microscope image shows system. our solar system. The differenc- rows and rows of atoms stacked side-by-side.