2022 Astronomy/Astrophysics
The pre-recorded talks and posters on this page showcase the work of students who received NC Space Grant research funding during 2021-2022. The menu at right provides links to pre-recorded talks and posters by other funded students on additional topics.
Madyson Barber
2021-22 NC Space Grant Undergraduate Research Scholar
University of North Carolina at Chapel Hill
Undergraduate Student (Senior), Astrophysics and Computer Science
Transit Hunt for Young and Maturing Exoplanets (THYME) VIII: A Pleiades-age Association Harboring Two Transiting Planetary Systems from Kepler
We describe a young association (MELANGE-3) in the Kepler field harboring two transiting planetary systems (KOI-3876 and Kepler-970). We initially identified MELANGE-3 by searching for kinematic and spatial overdensities around stars with high levels of lithium (in this case, KOI-3876). To better determine the age and membership of MELANGE-3, we combine archival light curves, velocities, and astrometry, with new high-resolution spectra of stars nearest KOI-3876 spatially and kinematically. The resulting rotation sequence, lithium levels, and color-magnitude diagram of members are all consistent with the Pleiades, confirming the population is co-eval and providing an age estimate of 105±10 Myr. MELANGE-3 may be one edge of the recently identified Theia 316 stream, also estimated to be approximately 108 Myr. For the two exoplanet systems, we revise the stellar and planetary parameters, taking into account the newly-determined age. We fit the 4.5 yr Kepler light curves and find that KOI-3876.01 is a 2.0±0.1R⊕ planet that orbits its star every 19.58 days, while Kepler-970 is a 2.8±0.2R⊕ planet that orbits its star every 16.73 days. KOI-3876 was previously flagged as an eclipsing binary, but we rule this out using radial velocities from APOGEE and statistically validate the signal as planetary in origin. Given its overlap with the Kepler field, MELANGE-3 is valuable for studies of spot evolution on timescales of years, and both planets contribute to the growing work on transiting planets in young stellar associations.
Faculty Advisor: Andrew Mann, University of North Carolina at Chapel Hill
Matthew Fields
2021-22 NC Space Grant Graduate Research Fellow
University of North Carolina at Chapel Hill
Graduate Student (Doctoral), Astrophysics
How Often Do Planets Form Misaligned with Their Host Stars?
Since the discoveries of the first exoplanets three decades ago, it has become clear that planetary systems are extremely diverse, especially compared to our own Solar System. Among the more puzzling discoveries are planetary systems whose orbits are misaligned with their host stars, i.e., the orbital axis of the planet(s) is offset from the rotation (spin) axis of the star. The planetary orbits of our Solar System are well-aligned with the Sun which is why the discoveries of misaligned systems stand out as particularly unusual. Most studies assume that these misalignments result from external gravitational disturbances (e.g., stellar flybys or wide binary companions) which occur after the planets are formed. Here, I present a method to measure the alignment between protoplanetary disks and their host stars to determine the statistical frequency in which planetary systems form misaligned. The method combines three stellar parameters (radius, rotation period, and projected rotation velocity) to calculate the stellar inclination, which is compared to the disk inclination to calculate alignment. To show that this methodology works, I perform several tests on a set of young stars (with ages ranging from ~3-600 Myr) with known parameters. This is an important first step toward applying the technique to a large collection of stars with resolved disks (and, hence disk inclinations) to estimate the statistical disk-star alignment distribution for star systems hosting protoplanetary disks.
Faculty Advisor: Andrew Mann, University of North Carolina at Chapel Hill
Benjamin Kaiser
2021-22 NC Space Grant Graduate Research Fellow
University of North Carolina at Chapel Hill
Graduate Student (Doctoral), Astrophysics
Ancient Extrasolar Planetesimal Compositions and Cosmological Implications
White dwarf stars present the unique opportunity to measure the bulk abundances of extrasolar rocky planets and planetesimals when the planetesimals are accreted by their host white dwarf. Five white dwarfs have accreted rocky planetesimals that were formed ~8 billion years ago. These planetesimals appear to be enhanced in lithium compared to the planets and meteorites in the Solar System, which are ~4.5 billion years old. The two explanations offered for this lithium excess were the following: Galactic nucleosynthetic evolution (Kaiser et al. 2021) and differentiation of the planetesimal into continental crust (Hollands et al. 2021). We present newly obtained spectroscopic observations of three of the white dwarfs: LHS 2534, WD J1824+1213, and WD J2317+1830, which confirm the previously published lithium detections. We also present the discovery of MgH in WD J1824+1213 and a newly obtained potassium limit. We provide an independent potassium limit for WD J2317+1830 that is compatible with the limit previously determined by Hollands et al. (2021). We also present newly determined total ages for all five lithium-polluted white dwarf systems using the new models of Bédard et al. (2020). We compare the measured abundances of the planetesimals accreted by these white dwarfs to both the Galactic nucleosynthetic evolutionary model and the expected lithium enhancement from differentiation. We demonstrate that differentiation is inadequate to produce the observed levels of lithium enhancement, and Galactic nucleosynthetic evolution could produce the observed levels.
Faculty Advisor: J. Christopher Clemens, University of North Carolina at Chapel Hill
Caleb Keaveney
2021-22 NC Space Grant Undergraduate Research Scholar
North Carolina State University
Undergraduate Student (Junior), Meteorology and Applied Mathematics
Modeling the Dynamics of Jupiter’s Great Red Spot with the EPIC Atmosphere Model
Jupiter’s Great Red Spot (GRS) is the oldest discrete meteorological phenomenon known to exist in the universe. Observed continuously for over 150 years, with possible sightings as early as the 1600s, the GRS is a high-pressure anticyclone sandwiched between Jupiter’s South Equatorial Belt and South Tropical Zone. While it remains the largest storm in the solar system, the GRS has significantly decreased in visible size over the past 100 years. The dynamics driving the Spot’s contraction are not well understood. Here, we present findings regarding the dynamical structure of the GRS through numerical modeling. We use the Explicit Planetary Isentropic Coordinate (EPIC) atmosphere model to run simulations on a GRS-like model vortex embedded in the known Jovian zonal wind profile at the location of the GRS. In particular, we model the GRS as a Gaussian ellipsoidal perturbation on the Montgomery streamfunction, as done successfully by previous EPIC modelers in other cases. We have successfully generated a GRS-like vortex that is meteorologically and numerically stable on the order of several Jupiter days, and are in the process of manipulating this vortex to extend its lifetime. With the model vortex and atmosphere developed through this project, future studies can continue to offer insights into the dynamics that modulate the size of the solar system’s largest storm.
Faculty Advisor: Gary Lackmann, North Carolina State University
Reilly Milburn
2021-22 NC Space Grant Graduate Research Fellow
University of North Carolina at Chapel Hill
Graduate Student (Doctoral), Physics and Astronomy
Probing Planet Evolution Through Exoplanet Exosphere Detection
Of the approximately 4,900 confirmed exoplanets, there is an apparent dearth of intermediate sized planets that orbit close to their host stars. This “Neptunian Desert” could be explained by rapid photoevaporative mass-loss early in the lives of exoplanets with short orbital periods. We can probe these photoevaporative processes by measuring the transit at wavelengths where the escaping material should be opaque (e.g., Lyman-Alpha, H-alpha, He-10830). Using high-resolution telluric-corrected spectra taken during transit, we find a possible transit signal in H-alpha for HIP67522 b, a noisy signal for HD63433 b, and a non-detection for DS Tuc A b. We confirm this by testing our method on several photospheric lines less impacted by stellar variability. Non-detections could be due to ionization of the exosphere, strong stellar variability overwhelming a transit signal, or weaker-than-expected photoevaporative mass-loss.
Faculty Advisor: Andrew Mann, University of North Carolina at Chapel Hill
Stephen Schmidt
2021-22 NC Space Grant Undergraduate Research Scholar
University of North Carolina at Chapel Hill
Undergraduate Student (Senior), Astrophysics and Mathematics
Estimating M Dwarf Metallicities Using Wide Binaries and Gaia EDR3 Data
Tidal As the most common type of star in the Galaxy, M dwarfs have the potential to offer great insight into both Galactic chemical evolution and exoplanet populations. However, current methods for finding a star’s metallicity are difficult to apply to M dwarfs, due to overlapping molecular lines in their spectra. Broadly applicable methods to estimate metallicities are the preferred method for quickly determining large numbers of M dwarf metallicities without any additional observations. In this work, we use a set of >500 wide binaries selected using Gaia astrometry to derive a relation between color-magnitude position and metallicity for late-type stars. We incorporate large metallicity catalogs like APOGEE, SPOCS, and LAMOST to associate the primary stars’ metallicities to the secondary stars’ data, using overlapping stars between these catalogs to correct for offsets, and wide binaries within each catalog to check reported uncertainties. To account for unresolved binaries in the late-type companions, we used a mixture model, with one model corresponding to single M dwarfs and another for unresolved pairs. We are able to determine a companionless low-mass star between spectral types K5 to M9’s metallicity to within 0.12-0.15 dex, enabling the calculation of metallicities for millions of single M dwarfs with parallaxes from Gaia.
Faculty Advisor: Andrew Mann, University of North Carolina at Chapel Hill
Alex Sobotka
2021-22 Graduate Research Fellow
University of North Carolina Chapel Hill
Graduate Student (Doctoral), Physics and Astronomy
Observational Constraints for a Decaying Hidden Sector Particle During the Epoch of Radiation Domination
The Cosmic Microwave Background (CMB) provides direct insight into the evolution and composition of the universe at the time of recombination, 380,000 years after the Big Bang. Furthermore, measurements of the abundance of primordial elements place stringent constraints on the baryon and radiation energy densities at the time of Big Bang Nucleosynthesis (BBN). We determine to what extent these observations constrain the period between BBN and recombination. Motivated by theories that place dark matter in a hidden sector, we consider a hidden sector particle that decays into Standard Model radiation. We modified the Cosmic Linear Anisotropy Solving System (CLASS) Boltzmann code to include the evolution of this hidden sector species and place constraints on the particle decay rate and its maximal contribution to the energy composition of the universe. In doing so, we find that if the particle decays into a mixture of photons and massless neutrinos, then the Planck satellite’s measurements of the CMB anisotropies, along with measurements of the baryon-to-photon ratio at BBN and bounds on CMB spectral distortions, constrain the particle to contribute at most 2.5% of the energy density of the universe and the particle lifetime to be less than about 383 hours. However, lifetimes longer than this are allowed if the particle decays only into massless neutrinos. In both cases, the derived constraints are dominated by the injection of new photons and neutrinos rather than the decay’s alteration of the expansion rate.
Faculty Advisor: Adrienne Erickcek, University of North Carolina at Chapel Hill
A. Turchaninova
2021-22 NC Space Grant Graduate Research Fellow
University of North Carolina at Chapel Hill
Graduate Student (Doctoral), Physics
Using the Cosmic Microwave Background to Probe the Universe’s First Second
The evolution of the early universe is largely unconstrained: there is a vast gulf between the energy scales of inflation and the onset of Big Bang nucleosynthesis. Among the theories proposed to fill this gap is a class of scenarios in which the universe is effectively dominated by matter during that time. An early matter-dominated era (EMDE) causes dark matter (DM) to cluster into dense structures called microhalos earlier than in a standard cosmology, increasing the DM annihilation rate for a given DM candidate. An EMDE broadens the range of viable DM candidates while also making more of these candidates accessible to indirect-detection methods, which search for energetic particles produced by DM annihilation. The cosmic microwave background (CMB) is particularly sensitive to injection of energetic particles that takes place before structures form in the absence of an EMDE. We demonstrate the constraining power of the CMB for EMDE scenarios via the temperature and polarization anisotropy spectra, as well as the reionization and thermal histories.
Faculty Advisor: Adrienne Erickcek, University of North Carolina at Chapel Hill