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This page is for people new to astronomy to see what I do.
The Power of Chemistry
The bulk of my research revolves around the idea that we can understand something about the star formation history of a stellar population/galaxy by measuring the abundances of the chemical elements in the atmospheres of individual stars. Stars form from gas that is nearly entirely composed of hydrogen and helium, but this gas also contains trace amounts of “metals”. Most astronomers consider all elements that are heavier than helium to be “metals”. These metals are forged in stars and/or explosions of stars (supernovae), and are ejected back to the interstellar medium (ISM). Eventually, gas in the ISM collapses to form new stars that are now enhanced in metals from the previous stellar generation.
Because the chemical abundances of a star generally stay the same throughout its lifetime, a measurement of the chemical abundance pattern of a star is a measurement of the chemical abundance pattern of the gas that was present in a galaxy at the time that star was formed! Furthermore, since we know that not all elements are created equally in the Universe, we can use this chemical abundance pattern to back out what astrophysical processes occurred in that galaxy to make those elements.
Theoretical and observational work have provided us with the “Astronomer’s Periodic Table” (shown below), which shows where in the Universe each element is created.
While this is a very powerful tool in principle, in practice one much observe the chemical abundances of many elements for many stars in a galaxy…
The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
Much of my research uses data from APOGEE. APOGEE is a dual hemisphere, high-resolution, near-infrared spectroscopic survey tasked with observing some 500,000 red giant stars across much of the Milky Way Galaxy. The goal is to measure chemical abundances for 15-20 elements from these spectra so that we can piece together the star formation history of our Galaxy.
My work generally focusses on the chemical abundances of the nearby dwarf galaxies (Sagittarius Dwarf Galaxy and Magellanic Clouds) and the Milky Way halo, but I have started getting into understanding the Milky Way disk and bulge.
Also, since my initial job with APOGEE had me looking at spectra all day, I’ve teamed up with exotic spectra expert, Drew Chojnowski, to identify and understand some pretty weird stars.