March 30, 2017. 4:30PM. BPB-102. Prof. Isaac F. Silvera on Metalic Hydrogen

Hydrogen is the simplest and most abundant element in the Universe. Over 80 years ago Wigner and Huntington predicted that if solid molecular hydrogen was sufficiently compressed in the T=0 K limit, molecules would dissociate to form atomic metallic hydrogen. We have observed this transition at a pressure of 4.95 megabars. MH in this form has probably never existed on Earth or in the Universe; it may be a room temperature superconductor and is predicted to be metastable. Hydrogen makes up ~90% of the planet Jupiter. It is believed to occur as a layer of liquid metallic hydrogen surrounding Jupiter's core, responsible for Jupiter's magnetic field, with molecular hydrogen as the outermost layer. Descending through the atmosphere, a phase transition from liquid molecular to liquid atomic metallic hydrogen occurs as the pressure and temperature increase. This first-order phase transition to liquid metallic hydrogen is at intermediate pressures (~1-2 megabars) and temperatures of ~1000-2000 K. We have also observed this liquid-liquid transition, known as the plasma phase transition. We shall discuss the methods used to observe these phases of hydrogen at extreme conditions of static pressure in the laboratory, extending our understanding of the phase diagram of the simplest atom in the periodic table.

Prof. Isaac F. Silvera is the Thomas D. Cabot Professor of the Natural Sciences at the Lyman Laboratory of Physics at Harvard University

Prof. Lepp delivered the University Forum lecture: Supernova 1987A: Thirty Years Later

University Forum lecture looks back 30 years to the first time anyone since the days of Queen Elizabeth I was able to see a supernova with the naked eye.^*

Stephen H. Lepp is the chairman of UNLV's department of physics and astronomy. At 7:30 p.m. March 23, he will present "Supernova 1987A: Thirty Years Later" at the Marjorie Barrick Museum as part of the University Forum lecture series. Here, Lepp discusses what we learned from the first supernova visible to the naked eye in 400 years.

On Feb. 24, 1987, a supernova was discovered in the Large Magellanic Cloud. A supernova is an explosive end to a massive star. This supernova was bright enough to see with the naked eye, the first such in nearly 400 years and the first since the invention of the telescope. As such, this was the first bright supernova to be observed with modern scientific instruments. It was the first from which neutrinos were detected, the first in which molecules have been detected and the first where we have observations of the star before it blew up.

Stars begin their life in dense molecular clouds. These clouds, which exist between stars in our galaxy are basically star forming factories. Parts of the cloud can collapse to form dense objects which eventually burn hydrogen up to helium in the process of nuclear fusion. This is the most common configuration for stars, and almost all the stars you see in the night sky are undergoing this burning of hydrogen to helium.

Most of these stars are not massive enough to get temperatures high enough to burn anything beyond hydrogen, but the most massive stars will undergo a series of nuclear reactions burning elements all they way up to iron. Iron is the most tightly bound nuclei and so you cannot produce energy by converting iron to higher mass elements. The massive stars can undergo a processes called core collapse and the energy released out shines for a short time the entire galaxy. These explosions look like new stars and so were called nova or supernova.

In this talk we will cover the history of supernova observations and some interesting results from Supernova 1987A, along with some modern supernova research.

^{* From UNLV News Center}

Prof. Bing Zhang co-organized an Aspen meeting on Fast Radio Bursts

Prof. Zhang recently organized an Aspen Center for Physics conference "Fast Radio Bursts: New Probes of Fundamental Physics and Cosmology" on Feb.12-17, 2017. The conference hosted about 80 scientists from around the world to discuss the nature of Fast Radio Bursts, mysterious radio bursts discovered 10 years ago. The event was recently reported in the journals: Nature and Scientific American.