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Over the past decade the discovery of three unique stellar populations and a large number of confirmed pulsars within the globular cluster Terzan 5 has raised questions over its classification. Using the longterm radio pulsar timing of 36 millisecond pulsars in the cluster core, we provide new measurements of key physical properties of the system. As Terzan 5 is located within the galactic bulge, stellar crowding and reddening make optical and near infrared observations difficult. Pulsar accelerations, however, allow us to study the intrinsic characteristics of the cluster independent of reddening and stellar crowding and probe the mass density profile without needing to quantify the mass to light ratio. Relating the spin and orbital periods of each pulsar to the acceleration predicted by a King model, we find a core density of 1.58 +0.13 −0.13 ×10 6 M pc −3 , a core radius of 0.16−0.01 pc, a pulsar density profile n ∝ r −3.14 +0.52 −0.53 , and a total mass of M T (R ⊥ <1.0 pc) 3.0×105 M assuming a cluster distance of 5.9 kpc. Using this information we argue against Terzan 5 being a disrupted dwarf galaxy and discuss the possibility of Terzan 5 being a fragment of the Milky Way's proto-bulge. We also discuss whether low-mass pulsars were formed via electron capture supernovae or exist in a core full of heavy white dwarfs and hard binaries. Finally we provide an upper limit for the mass of a possible black hole at the core of the cluster of M BH 3 × 10 4 M .

This paper presents the first results from draw-a-scientist tests (DASTs) over five years that were used to measure the effect of 8-10 week long astronomy clubs and week long summer camps on 3 rd-5 th grade elementary school students' perceptions of scientists. We facilitated these DASTs prior to these clubs or camps, which provide a baseline for a student's initial conception of scientists, and once at the end, to determine whether their conception changed, possibly as a result of their involvement. In total we analyze 89 pairs of DASTs using a numerical grading scheme designed to quantify the presence of various features in the drawn scientist and their activities. We find that there is a gender imbalance in both the pre-and postclub drawings, with only 32% and 35%, respectively, of students drawing female scientists. We also find that a third to a half of the scientists have a stereotypical appearance and/or are performing stereotypical activities. Although we find insignificant changes (<5%) in most categories, we do find an 8% increase in the number of scientists that have a stereotypical appearance, which is worth following up, but a significant 12% decrease in the number of scientists who are performing stereotypical activities. In addition, we present some possible improvements to implementing DASTs and discuss other possible assessments that could provide a more direct method of gauging the effect of these astronomy clubs or camps.

Since their discovery in 1967, neutron stars have been of great interest to the scientific community for their extreme physical characteristics. With supra-nuclear core densities and magnetic field strengths anywhere from 10 9 to 10 15 Gauss, these objects exist on the boundaries of science as we know it. Of particular interest are those neutron stars with extraordinarily stable rotational periods of a few milliseconds. These millisecond pulsars are thought to be the end result of a neutron star that has accreted mass from a companion star, giving it the angular momentum needed to spin rapidly.While we are beginning to find more pulsars in the process of turning into millisecond pulsars in the spiral disk of the Milky Way, we have traditionally found more systems close to this evolutionary stage in massive star clusters known as globular clusters. The large stellar interaction rate within globular clusters effectively increases the chances that a pulsar will have a nearby companion to interact with. More than 15 years of observations have been accumulated of millisecond pulsars in globular clusters, with some systems containing as many as 37 known pulsars within their core (with evidence of many more yet to be discovered).My thesis is broken into three broad areas of study. The first is designed to take the more than fifteen years of pulsar data available for the globular cluster Terzan 5and use it to model the physical characteristics of the system. Terzan 5 is a unique globular cluster in that it is thought to be the remnant of a smaller galaxy that was By looking at the long-term orbital period evolution I have measured changes in the orbital period of the pulsars and their companions and related it to changes in the gravitational field between the two stars. As pulsars are highly degenerate forms of matter, this change must arise due to changes in the companion stars interior density.These density perturbations allow me to provide better constraints on models of similar stars; these results also help to rule out the existence of large deformations in the companion star due to magnetic field realignments.My final goal for my thesis is to determine the exact mechanism by which a pulsar's radio emission interacts with unbound gas given off by the binary companion star. In redback systems, outer layers of gas may be stripped from the companion star due to a stellar wind or interactions with the pulsar. This unbound gas can cause eclipses iv Abstract v that obscure radio emission from the pulsar at both regular and irregular intervals of its orbit. Using four of the six redbacks previously mentioned, I have analyzed hundreds of eclipses to produce average eclipse properties for my sample of pulsars.My goal is to use these average eclipse properties to produce better estimates on the typical amount of unbound gas in these systems, as well as predict the distribution of the gas in each system. If possible, we will also determine the most likely physical mechanism that is actually obscuring the emission from...