Galactic Chemical Evolution

As discussed previously, some galaxies are passive.  In other words, boring.  Most of the Milky Way’s satellite galaxies are just agglomerations of stars that aren’t doing much.  All of the action happened billions of years ago, when those stars formed.  At that time, turbulent clouds of gas were collapsing and expanding, and some of those clouds kept collapsing until they became individual stars.  All of that gas is gone today,…

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Using manganese to probe Type Ia supernovae

The death of a star As T.S. Eliot probably meant to say, “This is the way a solar-mass star ends / Not with a bang but with a whimper.” When a star like our sun runs out of fuel, it eventually puffs up and releases its outer layers, leaving behind a dense inner core called a white dwarf. In isolation, this white dwarf isn’t particularly interesting. It’s no longer fusing…

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Heavy Metals

Welcome to Caltech’s Galactic Archaeology blog!  In this inaugural post, I’d like to explain what we mean by galactic archaeology. We spend lots of time measuring the composition of stars.  Specifically, we pick several elements and attempt to figure out how much of that element is present inside of a star or a galaxy.  Different elements encode different information about the star because different elements have different cosmic origins.  In…

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