The Big Bang produced only hydrogen, helium, and trace amounts
of lithium.
Everything else - from the carbon in our cells and the oxygen
we breathe to the silicon in our computers and the iron in our
infrastructure - was synthesized in stars through the nuclear
reactions they facilitate.
This is what Carl Sagan meant in his famous quote
"We are made of star-stuff."
My research sits at the intersection of astrophysics and
nuclear physics, seeking to understand which nuclear reactions
occur when, where, and under what astrophysical conditions.
By their very nature, the nuclear reactions powering stars and
occurring in the wake of supernovae change the chemical
composition of the material.
This material is ultimately expelled as gas back to the host
galaxy's interstellar medium, where it can be incorporated into
the next generation of stars and planets that will condense out
of the gas.
Being the sites of star formation and supernovae in the
universe, galaxies are like petri dishes of their own nuclear
reactions, retaining the nuclear products that come out of
their own stars.
By studying the present-day chemical content of the stars and
gas within galaxies, we can learn about the history of nuclear
reactions that gave it such a composition.
This graphic, produced by my colleague and advisor
Jennifer Johnson, illustrates which
elements are produced by which astronomical phenomena and in
what relative amounts.
The majority of this work sits in a field called
Galactic Archaeology, which studies this very
connection between a galaxy's evolutionary history and its
present-day chemical composition with particular interest in
our home galaxy - the Milky Way.
Revolutionary big-data surveys such as
APOGEE and
GALAH have collected and continue to collect spectra for
millions of stars, and by combining these spectra with models
for stellar atmospheres, we can estimate their chemical
compositions.
Other surveys such as
MaNGA collect similar data for external galaxies.
By comparing galactic evolutionary models which track nuclear
processes to data such as these, we can deepen our
understanding of physics on both galactic and nuclear scales.
Links to my publications in peer-reviewed scientific journals
can be found
here.
Recently, I expanded my research efforts beyond galactic
archaeology to the supernovae themselves.
In this endeavor, I'm collaborating with Ohio State's
revolutionary
All Sky Automated Survey for Supernovae
(ASAS-SN).
In particular, I'm studying the thermonuclear detonations of
white dwarf stars (type Ia supernovae) from a statistical
perspective.
These supernovae are known to produce much of the iron, nickel,
and zinc in the universe, and are known to arise more frequently
in low-mass, star-forming systems
(e.g.
Mannucci et al. 2005;
Brown et al. 2019).
The origin of this result is, however, something of a mystery:
is it purely because of the different star formation histories
of galaxies of different masses and morphologies?
Or is it that low-mass galaxies are known to have low metal
abundances (e.g.
Andrews & Martini 2013) and the
binary star systems - the progenitors of type Ia supernovae -
are more abundant where metal abundances are low
(
Badenes et al. 2018;
Moe, Kratter & Badenes 2019)?
Stay tuned for the results!
