March 10, 2015 3:30 BPB-217. Jason Steffen, Properties of exoplanets and systems with Kepler

NASA's Kepler mission has revolutionized the field of exoplanets and its discoveries give new insights into our theories of planet formation and dynamical evolution. With over 4000 planet candidates and 1000 confirmed planets, the variety of systems and planets shows the breadth of properties that planet formation models must encompass. I present some of the landmark results of the Kepler mission, especially relating to the planet masses and orbital architectures of the planetary systems. I discuss how these results affect our understanding of the solar system and of planets in general.

March 6, 2015 3:30PM BPB-217. Samaya Nissanke, Follow the chirp: seeing and listening to the transient Universe

The mergers of binary compact objects (black holes, neutron stars, white dwarfs) are amongst some of the most violent events in the Universe. The physics driving these events in strong field gravity are extremely complex, rich but still remain elusive. These cosmic laboratories present us now with both a challenge and an opportunity. The challenge is to explain the physics at play in strong-field gravity in Universe. The opportunity is to detect the accompanying radiation and panoply of multi-messenger particles (high energy neutrinos, cosmic rays and gravitational waves) for the first time with a suite of time-domain telescopes and experiments. In this pivotal new era of multi-messenger astronomy, the most compelling astrophysical sources are neutron star binary mergers, which should emit both in electromagnetic (EM) and gravitational waves (GW). I will first review the most recent advances in this blossoming field of EM+GW astronomy, which combines two active disciplines: time-domain astronomy and general relativity. I will discuss the promises of this new convergence by illustrating the wealth of astrophysical information that a combined EM+GW measurement would immediately bring. I will then outline the main challenge that lies ahead for this new field in pinpointing the sky location of neutron star mergers using GW detectors and EM wide-field synoptic surveys.

March 6, 2015 10:00AM BPB-217. Jean-Michel Desert, New Frontiers in Exoplanetary Science

The field of exoplanetology has recently transitioned from the investigation of individual objects to statistical studies. However, answers to key questions in exoplanetary science come not only from the statistics of discovery surveys, but also from the detailed characterisation of individual systems. I argue that the study of exoplanet atmospheres and their diversity is the next step in leveraging their detections. This is because a planet's atmosphere provides a fossil record of its primordial origins and controls its fate, size and appearance. The study of exoplanet atmospheres thus is crucial to answer fundamental questions in planetary formation and exoplanetary physics. In this context, I present new results from ongoing comparative exoplanetology programs that aim to characterise planetary systems transiting nearby stars through the observations of their atmospheres. This is achieved by combining ground- and space-based multi-wavelength observations secured over wide spectral regions. The results on the atmospheric composition and physical properties provide insights into the formation and evolution of planetary systems and enhance our understanding of our own Solar System's formation. Finally, I also present strategies for probing rocky exoplanet atmospheres orbiting in the habitable zone of their parent stars, and for searching for bio-signatures with future facilities.

February 20, 2015, 9:30AM BPB-217, Patricia Kalita, Ph.D. Defense

High Pressure Behavior of Mullite-Type Materials: Phase Transitions, Negative Linear Compressibility, Amorphization and Other Microstructural Implications

Even though mullite occurs rarely in natural rocks, it is perhaps one of the most important phases in both traditional and advanced ceramics and thus one of the most widely studied ceramic phases. Existing and emerging applications include: high temperature materials, aerospace materials, ballistic shielding components and even non-linear optical materials. There are many uncertainties regarding the basic physical properties of mullite-type materials, particularly in terms of their high-pressure phase stability and mechanical behavior that are important to address for new applications of mullites as an engineering materials. This work presents results of structural investigations of mullites and mullite-type materials at extreme pressures using synchrotron x-ray diffraction and laser Raman spectroscopy. The two experimental techniques used in this work are ideally suited to provide a synergical interplay in the study of mullites under high-pressure conditions: Raman spectroscopy is a technique for investigating short range order phenomena while x-ray diffraction accesses phenomena occurring at the long range order. Outcomes discussed include pressure-driven amorphization, phase transitions and negative linear compressibility.

February 27, 2015: Shri Kulkarni, Russell Frank Lecture Series

Professor Shri Kulkarni Director of the Caltech Optical Observatories will present a lecture entitled "The Restless Universe and the Palomar Transient Factory”

7:30pm Friday February 27 Bigelow Physics Building

Cosmic explosions were first noted nearly two thousand years ago Together, supernovae and variable stars have contributed richly to key problems in modern astrophysics: distances to galaxies, cosmography and the build up of elements in the Universe.

The Palomar Transient Factory (PTF), an innovative 2-telescope system, was designed to explicitly to chart the transient sky with a particular focus on events which lie in the nova-supernova gap. The PTF is now finding an extragalactic transient every 20 minutes and a Galactic (strong) variable every 10 minutes. The results so far: ultra-luminous supernovae as the end of the most massive stars in the Universe, progress in understanding the origin of Ia supernovae (which were used by astronomers to discover dark energy), and the identification of curious events of value to future gravitational wave observatories in space.

Admission is free. This talk is intended for a general audience including enthusiasts of all backgrounds and ages.

best regards
George Rhee

Jan 30, 2015 Forum: Fulvio Melia, The Zero Active Mass Condition in FRW Cosmologies

Abstract: The standard model of cosmology is based on the Friedmann-Robertson-Walker (FRW) metric. Often written in terms of co-moving coordinates, this elegant and highly practical solution to Einstein's equations is based on the Cosmological principal and Weyl's postulate. But not all of the physics behind such symmetries has yet been recognized. We invoke the fact that the co-moving frame also happens to be in free fall to demonstrate that the FRW metric is valid only for a medium with zero active mass. In other words, the application of FRW appears to require an equation-of-state rho+3p = 0, in terms of the total energy density rho and total pressure p. Though the standard model is not framed in these terms, the optimization of its parameters brings it ever closer to this constraint as the precision of the observations continues to improve.

UNLV Physics & Astronomy Forum is held in the conference room of the Bigelow Physics Building, BPB-217 at 3:45PM.  Refreshments at 3:30.

Prof. Zhang was named an APS Fellow by the American Physical Society

A high honor awarded by the American Physical Society, APS Fellows are elected based on "outstanding physics research, important applications of physics, leadership in or service to physics, or significant contributions to physics education". Specifically, Bing Zhang was recognized 

"for his significant scientific contributions to the understanding of the physical mechanisms of high-energy astrophysical sources, especially the prompt emission and afterglows of cosmological gamma-ray bursts."

All 2014 APS Fellows, along with Bing's entry, can be seen here.