Open Access. Powered by Scholars. Published by Universities.®

Astrophysics and Astronomy Commons

Open Access. Powered by Scholars. Published by Universities.®

6,367 Full-Text Articles 15,222 Authors 485,246 Downloads 178 Institutions

All Articles in Astrophysics and Astronomy

Faceted Search

6,367 full-text articles. Page 5 of 193.

Astronomy For Educators, Daniel E. Barth 2019 University of Arkansas, Fayetteville

Astronomy For Educators, Daniel E. Barth

Open Educational Resources

Astronomy for Educators provides new and accomplished K-12 instructors with concepts and projects for low-cost, high-impact STEM classroom instruction that is built around the National Academies National Research Council's K-12 Framework for Science Education.


Late Delivery Of Nitrogen To The Earth, Cheng Chen, Jeremy L. Smallwood, Rebecca G. Martin, Mario Livio 2019 University of Nevada, Las Vegas

Late Delivery Of Nitrogen To The Earth, Cheng Chen, Jeremy L. Smallwood, Rebecca G. Martin, Mario Livio

Physics & Astronomy Faculty Publications

Atmospheric nitrogen may be a necessary ingredient for the habitability of a planet as its presence helps to prevent water loss from a planet. The present-day nitrogen isotopic ratio, N-15/N-14, in the Earth's atmosphere is a combination of the primitive Earth's ratio and the ratio that might have been delivered in comets and asteroids. Asteroids have a nitrogen isotopic ratio that is close to the Earth's. This indicates either a similar formation environment to the Earth or that the main source of nitrogen was delivery by asteroids. However, according to geological records, the Earth's atmosphere ...


Dynamical Instability And Its Implications For Planetary System Architecture, Dong-Hong Wu, Rachel C. Zang, Ji-Lin Zhou, Jason H. Steffen 2019 Nanjing University

Dynamical Instability And Its Implications For Planetary System Architecture, Dong-Hong Wu, Rachel C. Zang, Ji-Lin Zhou, Jason H. Steffen

Physics & Astronomy Faculty Publications

We examine the effects that dynamical instability has on shaping the orbital properties of exoplanetary systems. Using N-body simulations of non-EMS (Equal Mutual Separation), multiplanet systems we find that the lower limit of the instability time-scale t is determined by the minimal mutual separation Kmin in units of the mutual Hill radius. Planetary systems showing instability generally include planet pairs with period ratio... (See abstract in article).


Ua1c2/36 Hardin Planetarium Photos, WKU Archives 2019 Western Kentucky University

Ua1c2/36 Hardin Planetarium Photos, Wku Archives

WKU Archives Collection Inventories

Images of Hardin Planetarium


Ua1c2/86 Bell Observatory Photos, WKU Archives 2019 Western Kentucky University

Ua1c2/86 Bell Observatory Photos, Wku Archives

WKU Archives Collection Inventories

Images of the Bell Observatory.


Numerical Simulations Of Convection With A Horizontal Magnetic Field, Talal Al-Refae 2019 University of Colorado, Boulder

Numerical Simulations Of Convection With A Horizontal Magnetic Field, Talal Al-Refae

Undergraduate Honors Theses

A numerical study of magnetoconvection with a horizontal magnetic field in a plane layer geometry is conducted. Novel dynamical regimes are observed beyond those occurring in classical (i.e non-magnetic) Rayleigh-Bénard convection. Imposed magnetic field strengths up to Chandrasekhar numbers of Q = 106 are investigated. The most unstable flow configuration is two-dimensional rolls oriented parallel to the direction of the imposed magnetic field in which the induced magnetic field is identically zero. The convective roll structure exhibits a preferential flow alignment along the direction of the imposed magnetic field thereby sustaining an anisotropic flow field. Deviations away from the ...


Robo-Ao M Dwarf Multiplicity Survey, Claire Lamman 2019 University of Colorado, Boulder

Robo-Ao M Dwarf Multiplicity Survey, Claire Lamman

Undergraduate Honors Theses

We analyze 6603 observations from Robo-AO’s M dwarf survey taken on the 2.1m Kitt Peak telescope and perform a multiplicity comparison with Gaia DR2. Through its laser-guided, automated system, the Robo-AO instrument has yielded the largest M dwarf multiplicity survey to date. After developing an interface to visually identify and locate stellar companions, we selected eleven low-significance Robo-AO detections for follow-up on the Keck II telescope using its NIRC2 imager. With Robo-AO, we find 550 candidate companions within 400 around 539 stars out of 5490 unique targets, most of which are new discoveries. Using a position cross match ...


Gemini, Michael Dalton 2019 Parkland College

Gemini, Michael Dalton

Natural Sciences Poster Sessions

This poster for the Natural Sciences Poster Session at Parkland College features the constellation Gemini, including a calculation of the change in rise time to determine the length of a year, determining the life span of the major stars in the constellation, identifying Messier objects within the region as well as the mythology behind the name of the constellation.


The Role Of Angular Momentum In The Interplay Between Disk Galaxies And Their Host Dark Matter Halos: Corollaries For The Hubble Fork Diagram, Angela Collier 2019 University of Kentucky

The Role Of Angular Momentum In The Interplay Between Disk Galaxies And Their Host Dark Matter Halos: Corollaries For The Hubble Fork Diagram, Angela Collier

Theses and Dissertations--Physics and Astronomy

A majority of disk galaxies host stellar bars that regulate and amplify the flow of angular momentum, J, between disks and their parent dark matter (DM) halos. These bars constitute the prime factor driving internal galaxy evolution. Yet, a non-negligible fraction of disks lack this morphological feature, which led to adoption of the Hubble Fork Diagram. The complex evolution of barred galaxies has been studied by means of numerical simulations, complemented by observations. Despite prolonged efforts, many fundamental questions remain, in part because cosmological simulations still lack the necessary resolution to account for resonant interactions and simulations of isolated galaxies ...


The Anthropic Principle And Multiple Universe Hypotheses, Oren Kreps 2019 University of Colorado, Boulder

The Anthropic Principle And Multiple Universe Hypotheses, Oren Kreps

Undergraduate Honors Theses

The universe appears to be fine-tuned for human life, which leads some to conclude that the universe must have been created for us. The Anthropic Principle is an attempt to dispel that argument, by stating that humans could only exist in a fine-tuned world and thus that it is not surprising that our world is (and seems to be) fine-tuned. I argue that to dispel the most surprising fine-tuning coincidences–those regarding the physical makeup of the universe–the Anthropic Principle requires that there be multiple universes, each with different physical characteristics. I further argue that some modern scientific hypotheses ...


Systematic Exploration Of The Inverse Cascade In Rapidly Rotating Convection, Mitchell Krouss 2019 University of Colorado, Boulder

Systematic Exploration Of The Inverse Cascade In Rapidly Rotating Convection, Mitchell Krouss

Undergraduate Honors Theses

A detailed investigation of the formation of large-scale vortices (LSVs) in rapidly rotating convection is carried out with an asymptotically-reduced model. The LSVs are generated by an inverse cascade of kinetic energy, which transfers kinetic energy from small length scales to large length scales. We can identify parameters, describing fluids, containing the presence of an inverse cascade by evaluating the transfer of kinetic energy to different wave numbers. We find a critical vertical Reynolds number that delineates the transition to flows which show a robust inverse cascade. The vertical Reynolds number can be fit with a multi-parameter power law, which ...


Comparison Of The Practical Applications And Limitations Of Insar And Structure From Motion Depictions Of Surface Elevation Flux For Academic Purposes, John Andrew Scherer 2019 University of Colorado, Boulder

Comparison Of The Practical Applications And Limitations Of Insar And Structure From Motion Depictions Of Surface Elevation Flux For Academic Purposes, John Andrew Scherer

Undergraduate Honors Theses

This paper seeks to identify the strengths and weaknesses of two remote sensing methods used for determining surface elevation flux (the difference in land surface elevation heights over a given time period): Interferometric Synthetic Aperture Radar (InSAR) and Drone Imagery processed using Structure from Motion (SFM) Techniques. This goal was accomplished by processing imagery from both platforms separately, before conducting a study of the same area and comparing the two methods analytically. A time-series of interferograms was generated on the study area of the Climax Mine and Mill near Leadville, CO and multiple drone flights were flown over an additional ...


The Relationship Between Radial Gas Pressure Gradient And The Planetesimal Mass Distribution Of A Protoplanetary Disk, Charles Abod 2019 University of Colorado, Boulder

The Relationship Between Radial Gas Pressure Gradient And The Planetesimal Mass Distribution Of A Protoplanetary Disk, Charles Abod

Undergraduate Honors Theses

The streaming instability is a mechanism that produces regions of particle overdensity in protoplanetary disks. These over-densities gravitationally collapse to form planetesimals. Although it is well known that the extent of particle clumping is dependent on the radial gas pressure gradient, the relationship between pressure gradient and planetesimal properties is not known. We carry out very high resolution local, shearing box simulations (i.e., a small co-rotating patch) of a protoplanetary disk to study the effect of the radial pressure gradient on the streaming instability and resulting planetesimal properties. We find that the pre-collapse structure of particles grows increasingly axisymmetric ...


Multiphase Cooling In A Large Halo, Jacob Moss 2019 University of Colorado, Boulder

Multiphase Cooling In A Large Halo, Jacob Moss

Undergraduate Honors Theses

The Cosmic Origins Spectrograph observations and The Hubble Space Telescope has detected OVI absorbers in the Circumgalactic Medium (CGM) of external galaxies, providiing evidence for large gas clouds outside galactic disks. These clouds may fall into the galactic disk, replenishing the gas that is consumed by forming stars. Large-scale galactic outflows are a signature of an active star-forming galaxy and are observed at all redshifts (Veilleux et al. 2005). Exploring a radially dependent pressure distribution of the confining pressure, Pcgm, suggests that outflows reach the outer halo or exit the galaxy if we assume an outflow velocity, v = 200 km ...


Multi-Diffusion Domain Modeling Of Meteorite 40ar/39ar Data, Evan Tucker 2019 University of Colorado, Boulder

Multi-Diffusion Domain Modeling Of Meteorite 40ar/39ar Data, Evan Tucker

Undergraduate Honors Theses

The majority of 40Ar/39Ar analyses involving extraterrestrial samples were collected from bulk rock samples due to fine grain sizes. This present challenges in modeling the diffusion kinetics and thermal histories of these samples because of the presence of multiple-diffusion domains. Since Lovera et al. (1989) developed the multi-diffusion domain (MDD) method of modeling, many attempts have been made to automate the modeling process. However, existing software to model diffusion parameters and thermal histories falls short in that it is either restricted in availability, restricted in flexibility, or is cumbersome to use. I have created a new program ...


Atlas Of Experimental And Theoretical High Temperature Methane Cross Sections From T = 295 To 1000k In The Near-Infrared, Andy Wong, Peter F. Bernath, Michael Rey, Andrei V. Nikitin, Vladimir G. Tyuterev 2019 Old Dominion University

Atlas Of Experimental And Theoretical High Temperature Methane Cross Sections From T = 295 To 1000k In The Near-Infrared, Andy Wong, Peter F. Bernath, Michael Rey, Andrei V. Nikitin, Vladimir G. Tyuterev

Chemistry & Biochemistry Faculty Publications

Spectra of hot methane were recorded using a tube furnace and a high-resolution Fourier transform spectrometer. We obtained experimental absorption spectra in the 1.85-1.11 μm near-infrared region at eight temperatures ranging from 295 K up to 1000 K. We have converted these into an atlas of absorption cross sections at each temperature for the methane tetradecad, icosad and triacontad polyads, excluding some spectral intervals either strongly contaminated by water or due to baseline fringes. On the theoretical side, the spectra were simulated from the ab initio-based Reims-Tomsk TheoReTS line list for the same experimental conditions. This line list ...


Satellite Maintenance: An Opportunity To Minimize The Kessler Effect, Bettina M. Mrusek Dr. 2019 Embry Riddle Aeronautical University

Satellite Maintenance: An Opportunity To Minimize The Kessler Effect, Bettina M. Mrusek Dr.

International Journal of Aviation, Aeronautics, and Aerospace

Recently, there has been an emphasis on the growing problem of orbital debris. While the advantages of placing satellites into space are numerous, advances in satellite technology combined with the growth of the industry have resulted with a significant amount of debris in the orbits surrounding our planet. The harshness of the space environment has also contributed to the debris, as evidenced by the number of objects currently in orbit which are not operational. As the amount of debris grows, so too does the likelihood of collisions, ultimately culminating in the Kessler Effect. However, recent advances in propulsion, advanced navigation ...


The Impact Of Hii Regions On The Interstellar Medium Of Our Galaxy, Matteo Luisi 2019 West Virginia University

The Impact Of Hii Regions On The Interstellar Medium Of Our Galaxy, Matteo Luisi

Graduate Theses, Dissertations, and Problem Reports

The interstellar medium (ISM) of our Galaxy contains low-density diffuse ionized gas known as the warm ionized medium (WIM). O- and B-type stars emit large amounts of ionizing radiation and it is believed that a fraction of this radiation escapes from their fully ionized HII regions and into the ISM where it is responsible for maintaining the ionization of the WIM. Here we aim to better understand how the radiation produced by OB stars is able to leak from the HII regions, how the radiation field changes during this process, and how the radiation affects the ambient ISM. Using Green ...


The Non-Linear Dynamics Of Barred Galaxy Evolution In Lcdm, Michael Petersen 2019 University of Massachusetts Amherst

The Non-Linear Dynamics Of Barred Galaxy Evolution In Lcdm, Michael Petersen

Doctoral Dissertations

The study of barred galaxy dynamics has had many successes explaining observed phenomena in barred galaxies both locally and distant, including our own Milky Way, a barred galaxy. However, the majority of this knowledge arises from either (a) analytic linear theory, which by definition cannot inform nonlinear processes, or (b) simulations which are subject to an unconstrained host of evolutionary mechanisms, including `real' dynamical processes and `artificial' numerical processes, and are thus difficult to interpret. This work chooses a path which attempts to take the best of both techniques, employing n-body simulations in the Lambda cold dark matter paradigm designed ...


Improving Photometry And Astrophotography By Eliminating Dark Frames And Flat Fields, Tom C. Ireland 2019 University of New Hampshire, Durham

Improving Photometry And Astrophotography By Eliminating Dark Frames And Flat Fields, Tom C. Ireland

Honors Theses and Capstones

I report on the efforts to improve the dark frames and flat fielding procedure for the charged-coupled device (CCD) camera for the Celestron C14 telescope at the UNH observatory. Dark frames are images taken while the shutter of the camera is closed so that only electronic and dark noise and other internal inconsistencies are recorded. These are important because they allow astronomers to subtract out interference from dark current. Additionally, flat fields are images of the entire field of the telescope so that the brightness in the pixels of the telescope’s field of view is uniform. Flat fields are ...


Digital Commons powered by bepress